Unit Converter

What the Unit Converter Does

Pick Length, Weight or Volume; the unit menus fill with that category's options, and the result updates live as you type. Length covers metre, kilometre, centimetre, mile, yard, foot and inch; Weight covers kilogram, gram, pound, ounce and tonne; Volume covers litre, millilitre, US gallon, US cup and cubic metre.

There is no rounding surprise to hunt for: the answer is shown to six decimal places with trailing zeros trimmed, and the maths is the same every time. Nothing is sent anywhere — the conversion happens entirely on your device.

How It Works

Every unit is stored as a factor relative to one base unit per category — the metre for length, the kilogram for weight, the litre for volume. To convert, the tool turns your value into the base unit (value times the 'from' factor), then out of it (divide by the 'to' factor). One multiply, one divide.

Those factors come from the standard definitions: an inch is exactly 25.4 mm, a foot 0.3048 m, a yard 0.9144 m, and a pound 0.45359237 kg (held here to six figures). Because the route always passes through the base unit, any pair in a category converts correctly without storing a separate factor for every combination.

Data source & conversion logic

Conversion factors are the internationally agreed definitions — the 1959 international yard-and-pound agreement (inch 25.4 mm, yard 0.9144 m, pound 0.45359237 kg) for imperial length and weight, US customary definitions for volume (gallon 3.785 L, cup 236.6 mL), and the metric tonne (1,000 kg). They are constants baked into the tool, so the result never depends on a network call.

1. Read the value and units. Take your number plus the chosen 'from' and 'to' units within one category (Length, Weight or Volume).
2. Convert into the base unit. Multiply by the 'from' factor to express the value in the category's base unit — metre, kilogram or litre.
3. Convert out to the target. Divide by the 'to' factor to land on the requested unit.
4. Round and show. Round to six decimal places, trim trailing zeros, and display the result live.

Conversion through a base unit

Results are rounded to six decimal places with trailing zeros removed. The mile and pound factors are held to six significant figures (true values 1609.344 m and 0.45359237 kg), so very large conversions can differ in the last digit.

Technical Details

Standards & references

• 1959 international yard and pound — fixes the inch at 25.4 mm, the yard at 0.9144 m and the avoirdupois pound at 0.45359237 kg — the basis for the length and weight factors.
• SI base units — the metre, kilogram and litre act as the base units each conversion passes through.
• US customary volume — the gallon (3.78541 L) and cup (236.588 mL) here are US, not imperial — a UK gallon is about 20% larger.

Accuracy & Limitations

Volume is US customary. The gallon is 3.785 L and the cup 236.6 mL — a UK (imperial) gallon is about 20% larger at 4.546 L, so do not use these for a British recipe or fuel figure.

'Ton' here is the metric tonne (1,000 kg), not the US short ton (907 kg) or the UK long ton (1,016 kg). Check which one your source means.

The mile and pound factors are held to six figures (1609.34 m, 0.453592 kg) rather than their full exact values (1609.344 m, 0.45359237 kg). The difference is microscopic for everyday use but can show in the last digit of a very large conversion.

Results round to six decimal places, so an exact fraction such as one-third of a unit is shown rounded, not as a repeating decimal.

It covers length, weight and volume only — not temperature, area, speed, data size, pressure or time. Temperature in particular is not a simple factor (it has an offset), which is why it is a separate tool.

Real-World Use Cases

When to use it — and when not to

Converting temperatures? Use the temperature converter — it needs an offset, not a factor. Need imperial UK volumes, or units outside length, weight and volume? This tool does not cover them.

Frequently Asked Questions

References

• International yard and pound (Wikipedia)
• Gallon — US versus imperial (Wikipedia)
• Tonne (Wikipedia)
• SI base units (BIPM)

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