Free construction calculators for UK builders
Five free calculators written against the Approved Documents for England. No signup, no limits, and each one tells you which document and edition its figures came from.
What each calculator checks, and what it does not
Each of the five does one job, and each page says which document it read.
- Roof pitch converts between degrees, ratio and fall, returns the true rafter length, and checks the pitch against the covering. That last check is against manufacturer minimums, because no Approved Document sets one.
- Stairs checks a private stair for a rise between 150mm and 220mm, a going between 220mm and 300mm, a pitch of no more than 42 degrees and the 2R+G rule, with the utility and general access limits alongside. Headroom and handrails are on the Part K guide, not in the calculator.
- Ramp takes the rise and returns the gradient, the number of flights and the landings between them. Approved Document M allows 1:20 up to 10m of going, 1:15 up to 5m and 1:12 up to 2m, so a 900mm rise at 1:12 needs more floor than most people have budgeted.
- Joist span is a take-off: joists at 400, 450 or 600mm centres, lineal metres and noggins. The joist size still has to come from a span table or an engineer, and the page tells you where.
- Extension cost refuses to run without your own rate per square metre, then adds fees, party wall, contingency and VAT. It will not invent a rate for you.
Using them well
Everything is in millimetres unless the field says otherwise. Nothing you enter is stored, and every one runs on a phone without an app. Where a result depends on a limit from an Approved Document, the result panel names the document and the edition, so you can check it against the copy your building control officer is working from.
What is not here yet
These five are the calculators where the English rule changes the answer. Concrete volumes, brick counts, tile counts and the rest of the geometry are the same in Leeds as in Melbourne, and the Australian set covers them with no regulatory figure attached. Scotland, Wales and Northern Ireland work to their own documents with different limits, and we have not built for them rather than guess.
Why a separate set of calculators
Geometry is the same everywhere. A 3-4-5 triangle squares a building in Manchester exactly as it does in Melbourne. What changes is the rule the answer has to meet: the maximum riser on a stair, the minimum pitch a tile can be laid at, the gradient a ramp is allowed to run. These calculators check against the local rule, so the answer you get is one you can build to.
Take the numbers into the job
Built Simple keeps your estimates, schedule and crew in one place, on the phone in your pocket.
Frequently Asked Questions
Are these calculators free? Yes, all of them, with no account and no limit on how many times you use them.
Which building regulations do they check against? The Approved Documents published for England. Each page names the document and the edition it used.
Can I use these for a job in Scotland? No. Scotland works to the Technical Handbooks, which set different figures. These calculators would give you the wrong answer.
