Universal Unit Converter
Fast · Accurate · SI & Imperial

About this Converter

Universal Unit Converter is built to be a fast, accurate companion for science, engineering, education, and everyday work. It supports modern SI (metric) alongside widely used US/Imperial units, with clear notes wherever context matters.

How we compute results

  • Exact definitions: inch = 0.0254 m; atm = 101 325 Pa; cal(th) = 4.184 J; hp(mech) = 745.69987158227 W.
  • High-precision math: calculations use Decimal arithmetic to avoid floating-point drift.
  • Affine handling: temperatures use proper offset+scale (K/°C/°F/°R).
  • Context locks: we block conversions that need extra info (e.g., VA → W without power factor; "standard" gas volumes without T/P).

What you can convert

Popular categories include:

Length Area Volume Mass/Weight Temperature Speed Time Energy Power Pressure Density Luminous Flux Illuminance Luminous Intensity Radiant Energy

See All Converters for full lists, spectral categories, and historic units.

Accuracy & sources

  • SI & standards: definitions follow BIPM, ISO, NIST and other standards bodies.
  • Temperature-specific columns: mercury at 0 °C (and 20 °C notes); water at 4 °C / 20 °C / 60-68 °F.
  • Photometry: cd, lm, lx handled consistently; historical "candle" units labeled.
  • Limitations: this tool is for general informational use; verify critical calculations.

Accessibility & UX

  • Keyboard-friendly: tab between inputs; selects support search.
  • Live updates: results announce via aria-live="polite".
  • Dark mode: toggle persists locally.
  • Copy result: one-click copy of the numeric output.

Changelog & versioning

  • v1.2.0 (2025-12-13): Modular engine with data-driven unit registry, alias mapping, and Decimal precision; dedicated pages pull from the shared registry.
  • v1.1.0: Added photometric and radiometric categories; improved accessibility and search.
  • v1.0.0: Initial launch with core SI and US/Imperial coverage.

See also: UI components, test suite.

Roadmap

  • More categories (torque, angle, viscosity, data rate, radiation dose).
  • Gauge vs absolute pressure mode; VA/var with power-factor input.
  • Gas volumes at reference conditions (SCF/Sm3/Nm3) with T/P selector.
  • Advanced/historic unit packs with tooltips.

Contact & credits

Built by Universal Unit Converter. Feedback and unit requests: universalunitconverter@gmail.com.

Powered by Decimal.js for high-precision math. SI definitions per BIPM; constants cross-checked against reputable standards sources.

Responsible use

This site is provided "as is." While we aim for accuracy, always confirm critical calculations with primary standards or engineering references.