Free UK Door Finishing Calculator

Architrave Calculator

Work out how much architrave you need for one door or multiple doors. Include one side or both sides, standard or custom door sizes, waste allowance, board quantities, cost guidance and an optional fitted estimate.

Built for DIY and trade Useful for one doorway, a whole house refresh, skirting and architrave jobs, and realistic buying plans.

Single or multi-door Useful whether you are trimming one doorway or planning a full property refresh.

Board comparison Compare 2.4m, 3.0m, 4.2m and 4.8m lengths to see likely quantities and spare.

Shopping list Get a copyable summary with board quantities, caulk, pins, paint guidance and costs.

Fitted estimate Add a broad installed cost guide using profile type, sides and project complexity.

Start with one door, then add more if needed. The calculator totals the two side legs and head piece for each doorway, applies any optional mitre allowance and waste, then converts the result into practical architrave board quantities.

Simple mode Quick answer using door size, one or both sides, waste and board length.

Advanced mode Add leg allowance, reveal allowance, mitres, board cost, fitted estimate and more.

Metric (mm) Imperial (inches) Single door Multi-door

Project setup

Board length

Waste allowance

Architrave type

Include paint guide?

Door measurements

Door 1

Door preset

Door height

Door width

Architrave sides

Advanced buying and costing

Allowance per mitre

Include material cost?

Include fitted estimate?

Include undercoat / primer note?

Estimated architrave needed

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Enter your door details to see total metres, board quantities and buying guidance.

Waste: —

Board length: —

Mode: simple

Project: single door

Project complexity meter

This helps show whether the project is fairly straightforward or likely to involve more joints, more waste and more fitting time.

Raw total before waste —

Mitre / extras —

Per door average —

Suggested target range —

Base architrave total—

Mitre and extra allowances—

Waste allowance—

Lengths required—

Estimated material cost—

Optional fitted estimate—

Board length comparison

2.4m lengths —

4.2m lengths —

Suggested buying and fitting direction

Enter your door details to see a practical architrave recommendation.

Layout suggestion

Best buying approach —

Practical note —

Practical guidance

A little extra architrave is usually safer than coming up short, especially when you are working through several doorways and trying to keep the profile, finish and joins consistent.

Practical doorway finishing guide

How much architrave do you need?

If you are trying to work out how much architrave to buy, the starting point is normally simple: two side legs and one head piece for each side of the doorway you are trimming. From there, you add any extra allowance for mitres, reveals, wider frame coverage, awkward cuts and normal waste.

This architrave calculator is designed to make that process more useful in the real world. Rather than only showing a raw metre total, it helps turn your door sizes into something practical: how many lengths to buy, which board lengths might reduce waste, whether the job is likely to need a bit more allowance, and what the overall cost may look like if you want a supply or fitted estimate too.

How this calculator works

Doorway first

The calculator starts with the doorway itself. It takes the door height and width, then builds the architrave total from the two side legs and one head section.

One side or both sides

Some jobs only need one face of the frame trimmed, while others need both. That makes a big difference to the total, which is why the sides selector matters.

Waste and mitres matter

Architrave is not only about raw lengths. Mitres, damaged ends, slight measuring differences and fitting choices all affect how many full lengths you should actually buy.

Typical architrave waste guidance

Job type	Typical allowance	Why it matters
One simple doorway	5% to 10%	Often enough where the frame is straightforward and the cuts are limited.
Several standard internal doors	10%	A practical middle ground for most homes where mitres and consistency matter.
Decorative profile or premium timber	10% to 15%	It is often worth allowing more so poor cuts or mismatched replacements do not slow the job down.
Older property with uneven walls or reveals	12.5% to 15%	Older openings and frame lines often need more trimming, scribing and correction work.
Whole-house refresh	10% to 15%	Buying a bit more helps keep the finish and profile consistent across multiple doorways.

Useful tools for decorating, trim and finishing work

Architrave calculator FAQ

How do I work out how much architrave I need?

The usual starting point is two side pieces and one head piece for each side of the doorway. Add those together, multiply by the number of doors, then allow extra for waste and mitres before converting the result into full board lengths.

Do I need architrave on one side or both sides of a door?

That depends on the job. Many internal doors have architrave on both sides, but some situations only need one side trimmed. The calculator lets you choose either option.

How much waste should I allow for architrave?

Around 5% to 10% is often enough for a simple doorway or a straightforward run of standard doors. For more decorative profiles, awkward openings, older walls or larger jobs, 10% to 15% is often safer.

Do mitres make much difference to the amount I should buy?

They can do. Every doorway usually involves mitred cuts, and those cuts create offcuts, trim loss and a bit of risk if the fit is not right first time. That is why mitre allowance is useful.

What length architrave should I buy?

Longer lengths can reduce joints and sometimes produce a cleaner result, but they may be harder to carry, transport and manoeuvre around stairs or tighter spaces. The best choice depends on the job and access.

Can I use this for several doors at once?

Yes. Multi-door mode lets you add several doorways together so you can plan a bigger decorating, carpentry or finishing project more easily.

Can this calculator estimate paint as well?

Yes, it can give a basic paint guide where that makes sense, especially for MDF, primed or paint-finish architrave. It is designed as a practical buying guide rather than a decorating specification.

How accurate is this architrave calculator?

It is designed to be a practical estimating tool and is much more useful than guessing from memory. It still does not replace measuring the real opening and checking the actual frame conditions on detailed jobs.