ScientificConverters.com Precise unit conversions for science & engineering.

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    How We Verify Conversion Factors

    This page explains where each conversion factor comes from, how it is stored and calculated, and how it is tested before every release.

    1. One factor per unit, relative to the SI

    Each unit is defined once, by its factor to the coherent SI unit of its category: pascal for pressure, cubic metre per second for flow, metre per second for face velocity, and so on. Any conversion A → B is then (factor A ÷ factor B). This avoids storing hundreds of pairwise factors that could disagree with each other.

    2. Exact definitions are stored as exact expressions

    Where a unit is exact by definition, the factor is stored as the defining expression, not a rounded decimal. For example:

    • psi = 0.45359237 kg × 9.80665 m/s² ÷ (0.0254 m)² = 6894.757293168361… Pa
    • torr = 101 325 / 760 Pa
    • US gallon = 231 × (0.0254 m)³ = 0.003785411784 m³
    • inch of water (conventional) = 1000 kg/m³ × 9.80665 m/s² × 0.0254 m = 249.08891 Pa

    Measured values, such as the inch of water at 60 °F (248.84 Pa), are taken as published by NIST and flagged as approximate on every page that uses them.

    3. Reference conditions are explicit

    Manometric units depend on the density of the liquid. We use the conventional definitions (water 1000 kg/m³, mercury 13 595.1 kg/m³, standard gravity 9.80665 m/s²) and state them on the page. Standard gas flows (sccm, SLPM) depend on the reference temperature and pressure; the default is 0 °C and 101.325 kPa (SEMI E12), and the converter lets you choose 20 °C and enter actual line conditions.

    4. Decimal arithmetic

    Calculations use the decimal.js library with 50 significant digits and half-even rounding. Results are rounded only when displayed: 10 significant figures by default, adjustable from 4 to 15. Very large and very small results switch to scientific notation.

    5. Automated tests on every build

    • Round trip: every pair in every category is converted A → B → A for several values; the result must match within a relative 10⁻¹².
    • Reference values: factors are checked against the values printed in NIST SP 811 Appendix B.8, to the number of digits NIST prints.
    • Exact identities: e.g. 1 L/(m²·s) = 1 mm/s and 1 ft³/(ft²·min) = 1 ft/min must hold exactly.
    • Data integrity: the build fails if any unit lacks a source, an id or slug is duplicated, or a worked example refers to a unit that does not exist.
    • Page checks: the build fails on duplicate titles or descriptions, a missing canonical URL, broken internal links or pages with too few internal links.

    6. Numbers in text are computed

    Numbers in FAQ answers and examples are not typed by hand. They are placeholders that the build replaces with values calculated from the stored factors, so the text cannot drift from the converter.

    Primary sources

    Found a discrepancy? Tell us. Corrections are logged in the changelog.

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