Bifold Door Sizes: A Complete Guide To Standard & Custom

Bifold doors don't come in one universal size. UK manufacturers offer a range of standard sizes plus bespoke options, and knowing which category your opening falls into changes what you pay, how long you wait, and how the buying process works.

This guide covers what "standard" actually means in the UK bifold market, the most common size options, how to measure your opening, what to do when your opening doesn't match a standard size, and the trade-offs of going bespoke.

What counts as a "standard" bifold size?

There isn't a single industry standard — but UK manufacturers have converged on a common set of widths and heights that get produced in volume. Most manufacturers offer standard bifolds at:

Widths: 1.8m, 2.1m, 2.4m, 2.7m, 3.0m, 3.6m, 4.0m, 4.2m, 4.8m, 5.0m, and 6.0m.

Heights: 2.0m and 2.1m are by far the most common. Some manufacturers offer 2.2m and 2.3m as standard, with anything taller usually classed as bespoke.

Standard sizes are cheaper because they're produced in optimised batches with pre-cut frame extrusions, pre-drilled hardware positions, and known glazing dimensions. Bespoke sizes require individual planning, custom cutting, and typically a longer lead time.

The standard size chart

Combining widths and heights gives you the typical UK bifold standard-size grid. The most-ordered sizes are marked with an asterisk.

Popular sizes marked with ★.

The 3m × 2.1m size is the single most common bifold order in the UK — it corresponds to the width most kitchen extensions get built at, and 2.1m is the standard door head height in modern construction.

How to measure your opening

Standard bifold sizes are quoted in frame dimensions — the size of the door frame itself. Your opening needs to be slightly larger to fit the frame plus a small tolerance for packing and levelling.

The rule: your structural opening should be 10mm wider and 10mm taller than the frame you're ordering.

Taking measurements:

1. Measure the width at three points: top, middle, and bottom of the opening.

2. Measure the height at three points: left, centre, and right.

3. Use the smallest of each set — the size the frame needs to fit into.

Openings are rarely perfectly square. A 3-metre-wide opening might measure 3,005mm at the top and 2,995mm at the bottom. The frame needs to fit the smaller dimension, so you order to 2,995mm minus 10mm tolerance = 2,985mm frame size, or the nearest standard down.

Checking for square: measure the two diagonals. They should be equal to within 5mm. If they're not, the opening isn't square and needs correcting before the doors go in, or the doors won't fit properly regardless of size.

When to measure: ideally, after structural work is complete but before internal plastering and rendering. Getting an accurate measurement of a finished opening is much easier than trying to work from plans.

Height matters as much as width

Buyers usually focus on width first — the length of the visible opening. But height is equally important for how the doors look and perform.

Standard 2.0–2.1m: Sits at the same height as most modern internal doors and window heads. Balanced, unobtrusive.

Extended 2.2–2.4m: Taller-than-standard configurations increasingly popular in new builds and extensions. Adds drama and lets in more light but changes the proportions of the room dramatically. Usually costs 10–20% more than the standard-height equivalent.

Bespoke over 2.5m: Available from most manufacturers but well into premium pricing territory. Frame engineering has to be strengthened to handle the extra glass weight, especially with 4+ panels.

For extensions, work back from the ceiling height. The frame head needs at least 100mm of clearance below the finished ceiling for the running gear, lintel, and any curtain or blind fitting.

When your opening doesn't match a standard size

Options in rough order of cost, cheapest to most expensive:

Option 1: Adjust the brickwork to fit a standard size. If you're already building an extension, or having structural work done, it's often cheap for the builder to adjust the opening by 20–100mm to hit a standard size. A 3,050mm opening becomes 3,000mm with a couple of bricks trimmed off — and you save the bespoke premium.

Option 2: Order the next standard size down and pack the difference. For small variations (say, 50mm), some fitters will pack the frame out with additional insulation and cladding to fill a slightly larger opening. Not always neat, and can create a visible frame border around the doors, but avoids the bespoke cost.

Option 3: Order a bespoke size. The right answer for non-standard openings where adjusting the brickwork isn't practical, or for buyers who want a very specific finish. Typically adds 15–25% to the price and 1–2 weeks to the lead time.

Option 4: Redesign the extension to fit a standard bifold. For new builds, work backwards from a standard bifold size. Adjust wall thickness, lintel width, or extension footprint by 100–200mm to match a standard door — it saves money and simplifies the schedule.

The cost of bespoke

Bespoke bifold pricing depends on how far from a standard size you're deviating. Some rough guides:

• Small variations (up to 100mm from a standard size): typically 5–15% premium.

• Moderate variations (up to 300mm): 15–25% premium.

• Non-standard dimensions (wider than 6m, taller than 2.4m): 25–50% premium, plus longer lead times.

• Fully bespoke (unusual proportions, corner configurations): case-by-case pricing.

Bespoke also usually means a lead time of 5–6 weeks rather than 3–4, because the doors have to be individually planned and cut.

Sizes vs configurations — don't confuse them

Two decisions get made together but aren't the same:

Size is the physical dimension of the frame — the width and height.

Configuration is the panel count, fold direction, and hardware — 3 doors folding left, 4 doors folding both ways with a traffic door, and so on.

The same size can accommodate different configurations. A 3m × 2.1m opening can be a 3-panel set or (with narrower panels) a 4-panel set. The configuration affects the look, price, and function of the finished doors as much as the size does — see our panel configuration guide for the detail.

Common questions

What's the maximum size of a bifold door?

Most UK manufacturers cap standard bifolds at 6m wide and 2.4m tall. Beyond that, you're into bespoke — some specialist manufacturers make bifolds up to 7-8 metres wide, but engineering, weight, and cost all step up significantly.

What's the smallest bifold worth having?

Around 1.8m wide is the practical minimum — below that, you're better off with French doors or a single hinged door, both of which are cheaper and just as practical for small openings.

Can I get a bifold in a non-standard height?

Yes, but expect a 10–25% cost premium and a longer lead time. If you're in a renovation or new build, consider adjusting the head height to match a standard bifold — it usually saves money overall.

How much clearance do I need above and around the doors?

Above: at least 100mm above the frame head for the lintel and running gear. Sides: 20–30mm each side for the jamb fixing and packing. Below: the threshold and cill combination sits on top of your floor structure, so the finished floor height changes.

What if the opening isn't square?

The doors won't fit properly without correction. Either the opening needs to be squared up (typically by re-plastering or rebuilding one jamb), or the doors have to be manufactured to the smallest workable size and the gap packed out — which is rarely a good outcome. Better to fix the opening before ordering.

Are wider doors always more expensive per metre?

Roughly proportional, but with a small premium for wider openings because the individual frame extrusions and glass units are longer and heavier. A 6m × 2.1m bifold costs slightly more per metre than a 3m × 2.1m equivalent, mostly due to the additional panels and running gear.

Can I have a bifold that's wider than it is tall?

Almost every domestic bifold is wider than tall. A 3m × 2.1m door is standard. Some very small bifolds (2m × 2.1m) are actually taller than wide — but generally, bifolds are landscape-format products.

Find the size that fits your opening

Our full size range from 2.1m to 6m is available direct from our Derbyshire factory, with bespoke options for anything in between. Configure your size, panel count, and finish on the product pages — pricing updates live as you choose.