How the math is computed.

Every conversion uses constants ratified by the Bureau International des Poids et Mesures, defined since the 2019 SI redefinition. Length derives from the speed of light in vacuum (c = 299 792 458 m/s); mass from Planck's constant (h = 6.626 070 15 × 10⁻³⁴ J·s); and so on across the seven base units.

Where a definition has changed historically — the international foot, the survey foot, the troy ounce — terican defaults to the modern internationally-agreed definition and labels alternates explicitly.

Conversions and calculator formulas are evaluated in arbitrary-precision arithmetic, then truncated or rounded only at the final moment of display — typically to six decimal places, or to a domain-appropriate convention (two for currency, three for engineering).

Each tool exposes a Precision control where you can request fewer digits for legibility or more for verification. The displayed digits never carry residual rounding error from intermediate steps.

Every formula on terican is open source and accompanied by its source on GitHub, plain-language derivation, and a worked example. The full set of constants is published as a CSV with each quarterly release.

Once a year, every tool is re-derived from primary sources and cross-checked against at least one independent reference implementation. Discrepancies — even at the sixth decimal — block the release.

• BLS, BIPM, NIST, and ISO publications for physical constants.
• Standard reference works for finance (Brealey, Hull) and statistics (CLT-based formulas).
• National guidance bodies for health (CDC, NHS, NWS) for tools like BMI and wind chill.

terican's calculators are reference tools. They are appropriate for learning, estimation, and cross-checking professional work, but should not substitute for personalised advice from a qualified accountant, doctor, lawyer, or engineer.

Every calculator page links its full formula and the assumptions it makes. If a calculation materially depends on circumstances we don't model, we say so on the page.