Tools that do the math and show their work
Published:
Free construction calculators — every formula stated, every worked example verified against published test vectors that run on every build. Imperial and metric, switchable mid-calculation.
Calculators
- Concrete Slab Calculator
Concrete slab volume in cubic yards or cubic meters, plus 80 lb, 60 lb, or 25 kg bag counts — free, imperial + metric, with waste factor.
- Rafter Length Calculator
Common rafter length from run and roof pitch (rise-in-12 or degrees) — line length, rise, and plumb-cut angle. Free, imperial + metric.
- Stair Layout Calculator
Riser count, exact riser height, treads, and total run from floor-to-floor rise — with IRC and DIN 18065 comfort checks. Free, imperial + metric.
What we found in 208,539 reviews
Before writing a line of app code we read the complaints. We scraped 737,216 app-store reviews, analysed the 208,539 in scope across 235 apps, and counted what field-app users actually object to — 28,412 of those reviews were one to three stars.
Every figure is a computed count with a published provenance ledger, and where the data contradicted what we expected, we say so. Read the research.
The apps we're building
No ads, no accounts, fully offline. Tenon Calc and Tenon Cam are pay-once: buy them and they are yours. Tenon Log — if it gets built at all — is one flat price for the whole firm rather than per seat, yearly or lifetime, your choice.
- Tenon Calc
Construction calculator that turns any calculation into a client-ready, branded PDF quote. Feet-inch-fraction math to 1/64, thirteen calculators, four of them free forever.
- Tenon Cam
Timestamp field camera. No ads, no vendor logo — your logo on the stamp — and whole projects export as a PDF photo binder.
- Tenon Log
The small-crew site diary: a day's record in under a minute, signed PDFs. Not per seat — your whole crew, one price. Not built yet, and not committed: a German waitlist decides it on 31 October 2026.
Get the mobile apps when they launch
Tenon Calc and Tenon Cam are pay-once. Tenon Log — if it gets built — is one flat price for the whole firm, not per seat. One email when each ships. Double opt-in, no spam, unsubscribe anytime.