About

This site exists to answer one question accurately in every form people ask it: how big is an engine? It turns bore, stroke and cylinder count into displacement in cc, litres and cubic inches, and refuses to fake the figures — power, fuel and tax that displacement cannot determine — that other tools invent.

Who is behind it

The tools and reference tables are maintained by Todd C. Thompson, working from published engine specifications, primary standards such as SAE J1349 and NIST SP 811 for units, and hands-on engine-build reference data. Where a figure is an estimate — horsepower, fuel consumption — the page shows the assumptions rather than a single confident number. Where it is illustrative — displacement-based vehicle tax — the page dates the review and points you to the official authority for the amount owed.

How the numbers are produced

Every calculation on the site runs through a single JavaScript core, engine.js, which is tested against known engines before each release: a Chevy 350 resolves to 349.85 cubic inches, a Honda K20 to 1998 cc and a perfectly square 1.00 bore/stroke ratio, a Mazda 13B rotary to 1308 cc, and one cubic inch to the exact 16.387064 cc. Keeping the maths in one audited place is what lets the whole site stay consistent and correct.

Our editorial line on honesty

Geometry is treated as exact. Estimates are labelled and given as ranges. Illustrative material is dated and caveated. Brand names appear only as search references, with no affiliation implied. If you find an error, the contact page is the fastest way to get it fixed.