There is no single legally mandated size for an internal door in the UK. What exists instead is a set of commonly stocked sizes, split between an older imperial family and a newer metric family, and a lot of houses that fit neither. Doors2Floors has supplied doors and flooring to homes and businesses across the UK, and sizing is still the single most common reason a door has to go back.
This guide sets out the exact sizes we actually stock, how to measure so you order the right one first time, and what to do when your opening does not match anything on the list. Our internal doors collection holds over 710 products, so almost every standard size is covered.
The two size families you will meet
Imperial sizes, still the default in older housing
Imperial leaves are 1981mm tall, which is 78 inches, with widths quoted in inches. Most UK housing built before the 1980s uses this family, and it remains the largest part of our range.
Metric sizes, common in newer housing
Metric leaves are usually 2040mm tall with widths in even hundreds of millimetres. Newer builds, flats and commercial fit outs are more likely to use these.
Why both still exist
Housing stock outlives standards. A country with terraces from the 1880s and apartments from last year needs both families, and manufacturers supply both.
Regional variation
Sizing conventions have never been perfectly uniform across England, Wales, Scotland and Northern Ireland, and older properties vary house by house rather than region by region. Measure rather than assume.
How to tell which family you have
Measure the height of an existing leaf. Close to 1981mm means imperial. Close to 2040mm means metric. Anything else means a non standard or altered opening.
Mixing the two families in one house
Extensions and loft conversions frequently introduce metric openings into an imperial house. This is normal and it means measuring every opening separately.
What this means for ordering
Order per opening, not per house. Our how to measure a door guide covers the method in detail.
The imperial sizes we actually stock
1981mm x 457mm, or 78 inches by 18
The narrowest standard leaf. Cupboards, airing cupboards and understairs stores. Available from £30.84 in our white primed range.
1981mm x 533mm, or 78 by 21
Still a cupboard width in practice. Too narrow for a room you carry furniture into.
1981mm x 610mm, or 78 by 24
Common on box rooms, small bathrooms and older cottages. Workable but tight.
1981mm x 686mm, or 78 by 27
One of the two most common domestic widths. Bedrooms, bathrooms and most internal openings in a terrace.
1981mm x 711mm, or 78 by 28
Less common but genuinely stocked in some ranges, including our internal oak doors.
1981mm x 762mm, or 78 by 30
The other very common width. Main bedrooms, living rooms and hallway openings.
1981mm x 813mm, or 78 by 32
Generous. Often used where a wider clear opening is wanted.
1981mm x 838mm, or 78 by 33
The widest common imperial leaf. Used on main reception rooms and where access matters.
An example across the range
The LPD Belize unfinished oak door is listed at £87.75 in every width from 457mm to 838mm, which is useful when a house has mixed widths and you want one pattern throughout.
The metric sizes we actually stock
2040mm x 526mm
The narrow metric leaf, typically for cupboards and service risers.
2040mm x 626mm
Smaller rooms and bathrooms in newer housing.
2040mm x 726mm
The workhorse metric width for bedrooms and most habitable rooms.
2040mm x 826mm
Wider openings, and the size most often specified where clear opening width is being considered.
2040mm x 926mm
The widest common metric leaf, used on principal rooms and accessible routes.
Metric fire door pricing example
Our LPD White Primed Flush Internal Fire Door is £87.39 at 2040mm x 526mm, 626mm and 726mm, £95.34 at 826mm and £103.28 at 926mm. Wider rated leaves cost more because there is more certified material.
Metric heights above 2040mm
Taller leaves exist for high ceilinged and commercial openings, and they move quickly into special order territory.
Do not convert and hope
726mm and 711mm are not interchangeable. A 15mm error is the difference between a door that closes and a door that binds.
Where the metric family dominates
Flats, student accommodation, offices and any project where fire rated leaves were specified from the start. See our over 240 fire doors.
Door thickness, the dimension people forget
35mm leaves
The standard domestic internal thickness in most of our range. Light, cheap to hang, fine for bedrooms and cupboards.
44mm leaves
Used for fire rated doors, heavier solid leaves and many commercial specifications. Noticeably better acoustically.
Why thickness changes more than you expect
A 44mm leaf in a lining set up for 35mm will foul the stop, sit proud of the frame, and may not accept the existing latch. It is not a straight swap.
Hardware follows thickness
Latch backsets, spindle lengths and lock cases are all thickness dependent. Check before ordering from our over 720 product locks and latches range.
Hinges follow thickness too
Heavier 44mm leaves want three hinges as standard. Our door hinges range holds 358 products, including over 20 butt hinges.
Fire doors and thickness
Rated leaves are thicker for a reason and the thickness is part of the certification. Never plane a rated leaf to fit a thinner lining.
Measuring thickness properly
Measure at the leading edge, not the hinge edge, and measure the leaf rather than the frame rebate.
Bi-fold and sliding thickness
Track systems have their own thickness limits. Our 16 sliding door kit systems and 15 bi-fold doors state theirs.
How to measure for an internal door, step by step
Step one: measure the existing leaf if there is one
If the current door fits and closes properly, copy its dimensions. This is the fastest reliable method.
Step two: measure the width in three places
Top, middle and bottom of the opening. Take the smallest figure. Old openings are rarely parallel.
Step three: measure the height in three places
Left, centre and right, from the finished floor to the underside of the head. Again, take the smallest.
Step four: measure the thickness
Measure the existing leaf, not the frame. 35mm and 44mm are the two you will normally find.
Step five: check for square
Measure both diagonals of the opening. If they differ by more than a few millimetres, the opening is out of square and the leaf will need scribing.
Step six: check the floor
Measure the gap under the existing door. If new flooring is going down, that gap changes. Decide flooring first.
Step seven: note the swing and hinge side
Stand outside the room looking in. Record which side the hinges are on and which way the door opens.
Step eight: write it all down per opening
Label each opening. Eight sets of numbers in your head becomes seven correct doors and one expensive mistake.
Step nine: allow for clearance
A hung door needs a small even gap around the top and sides and a slightly larger one at the bottom. Do not order a leaf that exactly fills the opening.
Step ten: choose the nearest size down, then trim
You can remove material. You cannot add it.
Trimming allowances and how far you can go
Every leaf has a stated allowance
Manufacturers publish how much can come off each edge. It is usually a modest amount on the stiles and rails, and it is not negotiable.
Why the allowance exists
Behind the facing there is a lock block and a frame. Cut past it on a hollow core and you open the leaf up.
Trim evenly
Take the same amount off both stiles. Removing 20mm from one side moves the panel pattern visibly off centre.
Height trimming
Take material from the bottom rail where possible, and only within the allowance.
Fire doors are different
Rated leaves have much tighter allowances and some cannot be trimmed at all. Exceeding the allowance can void certification. Our fire door materials guide explains the assembly.
Planing technique
Work from the ends towards the middle to avoid splitting the corner. Our guide on how to plane a door covers it properly.
Seal the cut edge
A trimmed edge on a primed or veneered leaf must be sealed or it will absorb moisture and swell.
When trimming is the wrong answer
If you need more than the allowance, order the correct size or have the opening altered. Read how to stop doors swelling before assuming a binding door needs planing.
Frames, linings and the structural opening
The leaf size is not the opening size
The structural opening has to accept the lining, the leaf and the clearances. Work outwards from the leaf.
Lining thickness matters
A lining set for a 100mm wall will not suit a 140mm wall. Our internal frames collection holds 32 products.
Door stops and rebates
A loose stop lining lets you adjust the closing position. A rebated frame does not.
Architraves cover the joint
They hide the gap between lining and plaster. Our 16 door architraves and the architrave guide cover profiles.
Reusing an existing lining
Usually the biggest saving in the job, provided it is square and sound.
Fire rated linings
Rated openings need a compatible frame with the correct seals. This is not the place to reuse an old lining.
Checking the lining is plumb
A level on both jambs takes thirty seconds and prevents a door that swings open on its own.
Widening an opening
Anything involving the head of the opening may be structural. Get advice from a qualified professional before cutting.
Fire door sizes and why they behave differently
The size is part of the certification
A rated leaf is tested at specific sizes in a specific frame. Changing the size changes the tested condition.
Our rated size range
Our over 150 FD30 fire doors cover both imperial and metric families, from £87.39. We also list 8 FD60 fire doors and over 50 glazed fire doors.
Threshold and edge gaps
Rated assemblies specify the gaps. Never block a threshold gap and never pack a rated leaf out with timber to close a gap.
Intumescent seals
The seal groove is part of the assembly. Never paint it, fill it or cut through it.
Hinges and closers
We list over 50 fire rated hinges and 4 door closers. A closer must close the leaf fully every time, from any angle.
Things you must never do
Never wedge or prop a fire door, never fit a floor stop that holds it open, never fit a cat flap or letter plate, never remove the closer, and never reglaze it yourself.
If a rated door slams
Do not disable the closer. See why fire doors slam.
Where to get the requirement confirmed
Fire door requirements vary by property, layout and use. Confirm with your local building control body, a fire risk assessor or another competent professional before ordering. Start with what fire doors are and where they are needed.
Clear opening width and accessibility
Clear opening is not the leaf width
The usable gap is the leaf width minus the door thickness in the open position, minus the stop and any hardware projection. It is always less than the leaf width.
Why it matters
Wheelchairs, walking frames, prams and furniture all care about the clear opening rather than the nominal size.
How to gain clear width without a wider opening
Rising butt hinges, offset hinges and removing a bulky stop can all add usable width. Our door hinges range includes options.
Lever handles rather than knobs
Levers are easier for anyone with limited grip. Our door handles guide covers the choice.
Thresholds
Level thresholds matter more than door width for many users. Trip hazards are the practical risk.
Rugs and mats near doorways
A loose rug at a doorway is a fall risk. Never place one at the foot of a staircase. Our living room rug guide covers safer placement.
Requirements vary
Accessibility requirements depend on the building type, its use and whether the work is new build, extension or alteration. Take advice from your local building control body or a suitably qualified professional rather than working from a general figure.
Planning ahead
If a wider opening is likely to be needed later, it is far cheaper to build it wide now than to alter it afterwards.
Reading a door listing without getting caught out
The size in the title is the leaf, not the opening
Every internal door we list is described by the leaf dimensions. The opening always has to be larger to allow for the lining and the clearances.
Both systems often appear together
A listing may read 1981mm x 762mm followed by 78 inches by 30. These are the same size expressed twice, not two options.
Width first or height first
Convention varies. If a figure is close to 1981 or 2040 it is the height, whatever order it appears in.
Price can change with width
Our LPD White Primed Flush door runs from £30.84 at 457mm to £44.75 at 838mm. Others hold one price across every width, as our oak LPD Belize does at £87.75.
Check the thickness in the specification
It is often below the size list rather than in the title. 35mm and 44mm behave very differently in the same lining.
Check glazing before assuming a size exists
Glazed versions of a pattern often come in fewer widths, because the glass unit has to suit the stile width. Compare across our over 280 glazed doors and over 420 unglazed doors.
Fire rated versions are listed separately
A rated leaf is a different product with a different size list, not an option on the standard door. See our over 240 fire doors and over 20 black fire doors.
Finish level affects nothing about size
Our over 350 fully finished internal doors and over 80 unfinished internal doors use the same size families. Finish is a separate decision, covered in our primed versus prefinished guide.
Pairs are quoted per leaf
A pair of 686mm leaves needs an opening for two doors plus a meeting stile allowance, not a single 1372mm opening.
Sizing considerations by door style
Flush doors
Available in the widest range of sizes and the most tolerant of trimming, because there is no pattern to throw off centre.
Shaker doors
Trim evenly or the stile widths become visibly unequal. Our 9 shaker doors start at £106.50.
Panelled doors
Panel proportion is set by the leaf width. A six panel pattern on a 610mm leaf looks cramped, which is why we list 19 4 panel internal doors, 10 6 panel internal doors, 6 2 panel internal doors and 4 3 panel internal doors as separate families.
Cottage and boarded doors
The most forgiving style for out of square openings, because the boarding pattern hides a scribed edge.
Glazed doors
Least forgiving. The glass unit fixes the stile and rail widths, so trimming is limited. Compare over 110 clear glazed doors, over 20 frosted glazed doors, 7 reeded glazed doors and 5 tinted glazed doors.
Laminated doors
A trimmed laminate edge shows the core, so cut with a fine blade and seal it. See our over 20 internal laminated doors.
Oak and walnut veneered doors
Trim carefully to avoid chipping the veneer. Our over 290 internal oak doors and over 30 internal walnut doors both benefit from a sharp plane and a sealed edge. Our oak versus walnut comparison covers the two timbers.
Coloured and painted doors
Trimming exposes bare material that must be repainted. Factor that in with our over 110 internal black doors and over 60 internal grey doors.
Where style meets size in practice
If your openings are narrow, choose a style that suits narrow proportions rather than forcing a wide pattern onto a small leaf. Our guide to internal door styles covers which patterns suit which proportions.
Ordering, delivery and pre fitting checks
Order every door at once
Colour, grain and finish vary between production batches. Splitting an order is how mismatches happen.
Check the delivery against your list
Measure each leaf on arrival against your written schedule before anything is cut.
Inspect for damage at the edges
Corners and bottom rails take the worst of transit. Report damage before fitting rather than after.
Acclimatise before hanging
Store leaves flat, off the floor, in the room they will be fitted in, for several days. This prevents most binding complaints later.
Do not store doors in a damp garage
Timber and MDF both take up moisture and then move once they are in a heated house.
Keep the labels and certification plates
Photograph the data plate on any rated leaf before decoration covers it.
Buy hardware at the same time
Handles, hinges, latches and stops in one order, in one finish, from our over 2,900 product door hardware range. Our over 2,500 door handles and over 30 door stops cover most needs.
Keep one spare leaf
If the pattern is discontinued later, one spare protects the whole floor. This matters most with our over 20 clearance doors.
Budget the fitting properly
Our guide to internal door fitting costs covers realistic labour, and our budget door guide covers where saving is safe.
Sizing in rentals, flats and commercial buildings
Standardise the size, not just the style
One leaf size across a portfolio turns replacements into a stock item rather than a survey.
Metric is usually the safer default
Newer flats and commercial fit outs are more likely to be metric, and rated leaves are widely available in that family.
Rated openings drive the schedule
Identify every rated opening first, then size everything else around what is available. Our over 150 FD30 fire doors and 8 FD60 fire doors are the starting point.
Corridors and back of house
Wider leaves and hard wearing faces. Our over 20 internal laminated doors are the usual specification.
Closers change the usable width
A closer arm and a rated stop both eat into the clear opening. We list 4 door closers.
Record everything
A written door schedule with sizes, ratings and hardware saves money at every future refurbishment.
Accessibility in shared areas
Requirements depend on building type and use. Get them confirmed by your local building control body or a suitably qualified professional rather than copying another building.
Brand consistency for matching later
Our largest ranges are LPD with over 500 products, Deanta with 258 and Mendes with 40.
Hardware standardisation
One family across the building. Our Carlisle Brass, Atlantic UK Hardware and Zoo Hardware ranges hold 1,461, 849 and 157 products respectively.
Which width suits which room
Understairs and airing cupboards
457mm or 526mm. Anything wider is wasted and often will not clear the stair string.
Box rooms and small studies
610mm or 626mm. Adequate for a desk chair, tight for a wardrobe.
Bathrooms and cloakrooms
610mm to 686mm is typical. Check the swing does not hit the basin or the pan.
Standard bedrooms
686mm or 726mm. This is the most common bedroom width in UK housing.
Main bedrooms
762mm or 826mm where the opening allows. Furniture access is the reason.
Living rooms and reception rooms
762mm to 838mm, or a glazed leaf to borrow light. We list over 280 glazed doors.
Kitchens
762mm or wider if you can. Appliances have to get in and out.
Utility and store rooms
610mm to 686mm. Cheapest sensible leaf.
Through lounges and open plan divisions
A pair or a divider rather than a single wide leaf. Our 17 room dividers and the French doors guide cover the options.
Integral garages and loft access
Size is dictated by the rated assembly available, not by preference.
Non standard openings and what to do about them
Why so many openings are non standard
Settlement, replastering, new flooring, and previous owners who trimmed a door to fit rather than fixing the opening.
Option one: nearest size down plus trimming
Works if the difference is within the allowance. This solves most cases.
Option two: adjust the lining
Packing or replacing the lining is often easier and cheaper than a bespoke leaf.
Option three: made to measure
Reliable and the most expensive route. Worth it for a principal opening in a period house.
Option four: change the door type
A sliding or bi-fold arrangement can suit an awkward opening better than a swing door. See our 16 sliding door kit systems and how bi-fold doors work.
Openings that are too tall
A transom panel above the door is usually neater than a bespoke tall leaf.
Openings that are out of square
Scribing the leaf to the opening is normal joinery. Expect it in any house over fifty years old.
Very old cottages
Low head heights and heavily out of square openings are common. Boarded leaves suit these better because they can be scribed freely. Our 11 cottage doors start at £55.99.
Listed buildings and conservation areas
Consent may be required before altering openings or joinery. Ask your local planning authority first.
Sizing space saving door systems
Bi-fold doors
Measure the finished opening, not the leaf. Our 15 bi-fold doors start at £131.35, and bi-fold door ideas covers layouts.
Sliding doors
You need wall space beside the opening equal to the leaf width plus the track overrun.
Pocket doors
The cassette dictates the wall thickness and the leaf size. Our 4 pocket doors start at £298.99 and are best specified at first fix.
Room dividers
Measure the full aperture including any structural upstand. Our 17 room dividers start at £498.06.
Ladder and boarded leaves
We hold 2 ladder doors, which are usually scribed to fit.
Head clearance for tracks
Track systems need headroom above the opening. Measure to the ceiling, not just to the head.
Floor guides
Sliding and pocket systems need a floor guide, which affects the flooring detail.
Sound and fire limits
These systems are generally unsuitable where a rated self closing leaf is required. Check before specifying.
External door sizes for comparison
External doors are a different family
Thicker, heavier, and sized around the frame rather than the leaf. Our over 90 external doors start at £86.79.
Composite doors are sold as sets
Leaf and frame together. Our 18 composite external doors start at £725.00.
Frames and cills
We list 2 external frames. Cill projection affects the finished height.
Side lights
These widen the structural opening considerably. We stock 1 product in doors with side lights.
Glazed external doors
over 30 products in glazed external doors.
Thermal performance
External sizing interacts with performance requirements. See our U values guide.
Costs
Our front door costs guide covers the budget side.
Do not use an internal leaf externally
It will delaminate. This is the most common false economy we see.
Common measuring mistakes
Measuring the frame instead of the leaf
The most frequent error and the easiest to avoid.
Measuring in one place only
Openings taper. Always take three measurements per dimension.
Forgetting the new floor
A new floor build up can remove all the bottom clearance.
Ignoring thickness
Ordering 44mm for a 35mm lining creates work you did not budget for.
Assuming all openings match
They rarely do, even on the same landing.
Rounding up instead of down
You can plane a door. You cannot stretch it.
Buying before deciding the hardware
Latch and lock cases have thickness and backset requirements. Check against our door hardware range of over 2,900 products.
Trimming a fire door to fit
Order the correct rated size instead. There is no safe workaround.
Not recording the hinge side
Handing matters on many rated and glazed leaves. See where to fit door hinges.
Frequently asked questions
What is the most common internal door size in the UK?
1981mm x 762mm and 1981mm x 686mm in imperial housing, 2040mm x 726mm in metric.
Is there a legal standard internal door size?
No. There are widely stocked conventional sizes, and separate requirements that can apply to fire safety and accessibility depending on the building. Confirm those with building control.
Are 1981mm and 2040mm interchangeable?
No. The difference is roughly 59mm, which is far beyond any trimming allowance.
What thickness should an internal door be?
35mm for most domestic internal openings, 44mm for fire rated and heavier solid leaves.
How much can I trim off a door?
Only within the manufacturer stated allowance, taken evenly from both sides.
Can I trim a fire door?
Only within its certified allowance, which is tight, and some cannot be trimmed at all.
What if my opening is between two standard sizes?
Order the smaller size and adjust the lining, or go made to measure for a principal opening.
Do you stock every size in every style?
No. Our over 710 internal doors cover the common sizes, but individual patterns list their own size options.
Should I decide the floor or the door first?
The floor. Our 12 product vinyl flooring range and the laminate mistakes guide explain why build up matters.
How many hinges for each size?
Two for a light hollow core, three for anything solid or rated.
What if the opening is out of square?
Scribe the leaf to the opening. It is normal work in an older house.
Where should I start?
Measure every opening, write it down, then read how to choose the right door.
Prices, product counts, stated sizes and availability are correct at the time of writing and are subject to change. Individual products list their own available sizes and trimming allowances. Fire door, accessibility and building regulation requirements vary by property, layout and use. Confirm your specific obligations with your local building control body, a fire risk assessor or another competent professional before ordering or altering any door or opening.