Instant, bidirectional unit conversion across seven categories — fast, private, and fully offline.
A premium, zero-dependency conversion workbench. Type a value into any unit field and every other unit in that category updates live, with real static conversion factors and correct non-linear temperature math — all in your browser, with nothing ever leaving your machine.
Unit Converter Pro is part of the Web Utility Suite. It runs entirely in the browser with no build step, no frameworks, and no network calls — open index.html from disk and it works. Pick a category from the tab bar, type into any field, and every other unit in that category recalculates instantly from a shared base-unit conversion engine.
- Seven categories: Length, Weight/Mass, Temperature, Area, Volume, Speed, and Digital Storage.
- Live bidirectional conversion — typing into any unit field instantly updates every other field in the category, driven by a generic base-unit engine (each category converts through one base unit; typed value → base → every other unit).
- Real static conversion factors — length (mm → nautical miles), mass (mg → US tons), area (mm² → mi²), volume (mL → Imperial gallons), and speed (m/s → knots), all using accurate real-world constants (e.g. 1 mile = 1609.344 m, 1 lb = 0.45359237 kg, 1 US gallon = 3.785411784 L, 1 acre = 4046.8564224 m², 1 knot = 0.514444 m/s).
- Correct temperature math — Celsius, Fahrenheit and Kelvin are non-linear, so they're converted with the real formulas (
C = (F−32)×5/9,K = C+273.15) instead of a bogus multiply table. - Dual-base digital storage — decimal/SI units (KB, MB, GB, TB, PB — 1000-based) and binary/IEC units (KiB, MiB, GiB, TiB, PiB — 1024-based) are both listed side by side, alongside bits and bytes.
- Clean number formatting — results are rounded to 12 significant digits and trimmed of trailing zeros and floating-point noise.
- Per-field copy buttons and a one-click Clear for the active category.
- Auto-persist — your last category and values are saved to
localStorageand restored on return. - Dark & light themes, fully responsive down to 360px, accessible, and keyboard-driven.
No dependencies, no build step.
git clone https://github.com/kasapdev/unit-converter-pro.git
cd unit-converter-proThen simply open index.html in any modern browser (double-click it, or file:// it). That's it.
- Pick a category from the tab bar — Length, Weight/Mass, Temperature, Area, Volume, Speed, or Digital Storage.
- Type a value into any unit field. Every other field in that category updates instantly.
- For Digital Storage, choose whichever decimal (1000-based) or binary (1024-based) units you need — both are always listed.
- Use Copy on any field to grab its formatted value, or Clear to reset the whole category.
- Your last category and values are remembered automatically for next time.
| Action | Shortcut |
|---|---|
| Length | Alt + 1 |
| Weight / Mass | Alt + 2 |
| Temperature | Alt + 3 |
| Area | Alt + 4 |
| Volume | Alt + 5 |
| Speed | Alt + 6 |
| Digital Storage | Alt + 7 |
| Clear current category | Alt + X |
| Show shortcuts help | ? |
| Close dialog | Esc |
Screenshots coming soon.
- Custom/user-defined units
- Copy-all as a formatted summary block
- Fuel economy and pressure categories
- Unit search/filter within a category
- Shareable permalink encoding the current category + value
MIT Licensed. Part of the Web Utility Suite.
One of 45+ zero-dependency vanilla JS tools, all free and open source — see the full list.