About PrecisionCalc

PrecisionCalc provides free, standards-based engineering calculators for mechanical designers, machinists and manufacturing engineers. Every calculator runs entirely in your browser: nothing is uploaded, stored or shared.

How the formulas are validated

Each calculator is backed by an automated regression test suite that compares outputs against published standard values and engineering handbook data. For example, the ISO 286 limits and fits calculator is checked against the ISO 286-1 table values for common sizes, and the metal weight calculator is checked against handbook mass-per-metre values.

What we deliberately do not do

We do not auto-generate low-value pages, and we do not hide unit conversions behind a paywall. Where a conversion is approximate by nature, such as Ra to Rz surface roughness, the page says so explicitly instead of pretending it is exact.

Planned Pro features

A paid Pro tier is planned with batch calculations, saved calculation history, PDF reports and a REST API. The free calculators will stay free.