About James Whitfield

I'm James Whitfield, and I build and review every calculator on Calculation Machine. I'm a former construction estimator based in Yorkshire, England, and I've spent the last decade working out quantities, angles and costs on real building sites — the kind of maths these calculators do, but usually done slowly with a clipboard and a calculator app that barely works.

Why I built this site

Most online calculators are built to farm ad clicks: huge pages, vague formulas, no sources and results that are quietly wrong. I got tired of double-checking everything they told me, so I started building my own tools where the formula is stated openly, the source is cited, and the numbers hold up. Calculation Machine is that collection, opened up to everyone — one question per calculator, clean pages, and no nonsense between you and the answer.

Experience and qualifications

I hold a BEng in Civil Engineering and spent over ten years in construction estimating and site engineering, covering concrete, landscaping, roofing and stair work. Alongside that I've taught applied maths to adult apprentices, which is where the habit of showing the working comes from. Every calculator on this site is built or personally reviewed by me — nothing is outsourced and no formula goes live without a cited source.

How the calculators are checked

Every formula is sourced, and every calculator is tested against worked examples before it goes live. The full process is on the methodology page.

Contact

Found an error or want a calculator added? Email hello@calculationmachine.com.