Standard interior door sizes: what to know before ordering

What door leaf widths are common on the market

Interior door leaves sold in Estonia are almost always made in a set of standard widths: 60, 70, 80 and 90 centimetres, measured as the leaf itself rather than the finished opening. Height is far less variable, with 200 centimetres being close to universal for interior doors, so the width is what you need to get right.

A 70 cm leaf is the usual choice for bedrooms and living rooms, 80 cm for a main entrance door within the flat or for anywhere a wheelchair or pram needs to pass, and 60 cm turns up mainly in narrow bathrooms, storage rooms or older builds where the opening simply was not made any wider. A 90 cm leaf is less common and mostly ordered for wide openings in newer housing.

How the frame and rough opening size differ from the leaf size

The leaf width is not what you measure on your wall. The frame (the casing that sits inside the wall opening and holds the hinges and latch) adds roughly 4 to 6 centimetres in width beyond the leaf, and the rough opening in the wall needs to be a little larger again to allow the frame to be shimmed level and packed with installation foam.

As a rough guide, a 70 cm leaf typically needs an opening in the region of 78 to 82 centimetres wide, but this varies by manufacturer and frame profile, so always check the specific product's installation dimensions rather than relying on a rule of thumb. Height works the same way: a 200 cm leaf needs an opening closer to 205 to 210 centimetres once the frame and packing are accounted for.

This is the step where most ordering mistakes happen. Someone measures the existing door leaf, orders the same number, and finds the new frame will not go into the old opening because the true opening size was never checked.

Why openings in older buildings rarely match a standard size

Wooden houses from the 1930s in areas such as Kalamaja and Nõmme, and Soviet-era panel flats from the 1960s to 1980s, were built to their own local conventions, often before the current standard range existed in its present form or built by hand without strict adherence to any catalogue size. Openings can be a few centimetres narrower or wider than any current standard, sit slightly out of square, or have settled and shifted over decades.

It is also common to find that a previous renovation altered the opening informally, packing it out with timber or plaster to fit whatever door was available at the time. The result is an opening that looks standard at a glance but measures awkwardly in practice, which only becomes clear once you take a tape measure to all four sides and the diagonals.

What to do when your opening matches no standard size

You have two realistic options. The first is to have the opening adjusted, usually by adding or removing a small amount of timber framing or plaster around the edge, so that it accepts a standard door and frame. This is often the cheaper and faster route, since standard doors are stocked and delivered quickly, and it is the approach we usually take on flat renovation and door installation jobs.

The second option is to order a custom-sized door leaf and frame made to your exact measurements. This avoids touching the wall opening at all but comes with a longer lead time, typically several weeks rather than a few days, and a noticeably higher price than a standard size, since it is a one-off production run rather than stock.

Which makes sense depends on how far off standard the opening is. A gap of one or two centimetres is usually cheaper to solve by packing out the frame; a genuinely unusual opening, common in older wooden houses with hand-built frames, may only be solved properly with a custom order.

• Measure the existing rough opening width, height and diagonal, not just the door leaf
• Check whether the opening is out of square before assuming a standard door will fit
• Get a quote for both adjusting the opening and for a custom door before deciding
• Ask the supplier for the exact frame and opening dimensions their standard sizes require
• Allow several weeks' lead time if a custom size turns out to be necessary

Other details worth checking before you place the order

Beyond width, check which way the door needs to open and hang, since a door ordered with the wrong hand will not simply flip round on site. Also check the wall thickness against the frame depth on offer: panel flats and wooden houses can have quite different wall thicknesses, and a frame that is too shallow or too deep for the wall will need extra trim to look right.

If the door sits near a bathroom or kitchen, consider whether you want a threshold strip for moisture or sound, and whether the existing floor covering height matches the new door's underside clearance. These are small details, but they are much easier to sort out before ordering than after the door has arrived.

Do you need permission to replace an interior door

Replacing a single interior door leaf and frame within a flat is generally not the kind of change that needs a building permit or notice to the building register, as long as you are not touching a load-bearing wall or altering the layout. We do not work on load-bearing walls, and if your project involves widening an opening in one, that is a job for a structural specialist, not standard door replacement.

If you live in a block of flats managed by an apartment association (korteriühistu), it is still worth checking their house rules, since some associations ask to be informed about renovation work in shared buildings even when no permit is required, and most set quiet hours that any noisy work such as cutting or chiselling out an opening should respect. When in doubt about whether a specific change needs formal permission, the city or the building register can confirm it directly.