Free Unit Converter

How It Works

All conversion math runs directly in your browser using a hand-written two-step algorithm — no library, no server call. Each of the 18 unit categories defines a base unit (metres for length, pascals for pressure, watts for power, etc.), and every other unit in that category stores two plain JavaScript functions: one to convert into the base, one to convert out of it.

1. 1
   Pick a category and units

   Choosing a category (length, temperature, energy, capacitance, and 14 others) loads that category's hardcoded unit table. Each unit entry carries a symbol, a display label, and two arithmetic functions — toBase and fromBase — baked directly into the source.
2. 2
   Two-step base-unit pivot

   When you type a value, the converter calls fromUnit.toBase(value) to reach the category's canonical base (e.g. metres, joules, amperes), then immediately calls toUnit.fromBase(baseValue) to arrive at the target unit. This single pivot works for any pair without storing an O(n²) table of direct ratios.
3. 3
   Result formatted to selectable precision

   The raw floating-point result is formatted with toPrecision(sig) where sig is 2, 4, 6, or 8 significant figures — your choice. Very large or very small results (outside 1e-10 to 1e15) switch automatically to exponential notation. An 'all conversions' grid simultaneously shows the input value converted into every unit in the category.
4. 4
   Conversion persisted and shareable via URL

   Your current category, units, and value are written into the URL fragment (e.g. #cat=length&from=km&to=mi&v=42) with a 300 ms debounce, so any conversion can be bookmarked or shared as a direct link without the value ever reaching a server. The last eight conversions are also saved to localStorage and appear as one-click history chips.

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