How accurate is TireFitLab?
Every calculator on this site reads its numbers from one shared, deterministic calculation engine. The same engine also generates the reference tables, so a tool result and a page table can never disagree.
One engine, automatically tested
All tire and wheel math lives in a single TypeScript package with no external dependencies. At the 2026-08-27 review it is covered by 118 engine unit tests (boundary, inverse and property tests included) plus 187 site-level tests, and every deployment must pass them — a release with a failing test cannot reach production.
What the numbers are based on
Geometry follows directly from the tire marking (section width, aspect ratio, rim diameter) using the standard nominal formulas; load-index, speed-symbol and rim-width tables follow published standards (UN R30/R54, ETRTO practice). Metric values are canonical; imperial values are converted for display only.
What accuracy does not mean
Results describe nominal geometry. A manufactured tire varies with brand, model, wear and pressure, and a calculation is never a vehicle-specific fitment, clearance or legal approval. Always verify against the vehicle placard, the manufacturer documentation and a physical check.
Verification gates on every release
Beyond the unit tests, each release re-validates generated structured data, hreflang reciprocity across all ten languages, internal links, performance budgets and honest review dates across the full page corpus. Found a number that looks wrong? Use the contact page — confirmed errors are fixed in the engine and the affected pages get an updated review date.