---
title: "Free Construction Calculators & Field Apps | Tenon Tools"
description: "Free construction calculators — concrete slab, rafter length, stair layout — and field apps on the way: Tenon Calc, Tenon Cam, Tenon Log. No ads, ever."
canonical_url: "https://tenon.tools/"
language: "en"
date_published: "2026-08-16"
last_updated: "2026-08-20"
source: "Tenon Tools"
---

# Tools that do the math and show their work

_Published: 2026-08-16_

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](https://tenon.tools/calculators/concrete-slab/): 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](https://tenon.tools/calculators/rafter-length/): 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](https://tenon.tools/calculators/stair-layout/): 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](https://tenon.tools/articles/)

## 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](https://tenon.tools/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](https://tenon.tools/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](https://tenon.tools/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.

Page: https://tenon.tools/ — this file is its markdown mirror. All mirrors: https://tenon.tools/llms.txt