# Unit Converter — Length, Mass, Volume, Area, Speed & Data

> Convert any unit instantly: metres, feet, kilograms, pounds, litres, gallons, m², acres, km/h, mph and more — all in one free universal converter.

- **Category:** Conversions & Units
- **Interactive calculator:** https://youcalc.com/en/conversions-units/unit-converter/
- **Price:** Free, no sign-up required

## Overview

This converter handles six measurement categories — length, mass, volume, area, speed, and digital data — in one place. Pick a category, enter a value and a starting unit, and every equivalent in that category appears instantly. Use it to check metric-to-imperial conversions, compare speeds, or translate data storage sizes without switching tools.

## How to read your result

The result panel lists all units in the chosen category alongside their converted values. The number you typed appears in its own row so you can scan the full range at once — from the smallest unit (millimetres, milligrams, bytes) to the largest (kilometres, metric tonnes, terabytes). Equivalent values that are very small or very large are shown in standard decimal notation so you can copy them directly.

## Method

The converter normalises every measurement to a base SI unit and then scales to the target. For length the base is the metre; for mass, the kilogram; for volume, the litre; for area, the square metre; for speed, the metre per second; for data, the byte. Each unit is associated with an exact multiplicative factor taken from NIST SP-811 and the BIPM SI Brochure — for example, 1 inch = 0.0254 m exactly, 1 pound = 0.45359237 kg exactly, and 1 US gallon = 3.785411784 L exactly. To convert a value from unit A to unit B, the value is first multiplied by the factor for A (giving the base-unit amount) and then divided by the factor for B. Because all factors are applied as exact constants and no intermediate rounding occurs, every unit in a category is derived from the same base-unit value, keeping all results mutually consistent.

## Example

- **Setup:** Enter 5 in the value field, choose the length category, and select ft (feet) as the source unit.
- **Result:** 5 feet converts to 1.524 metres, 152.4 centimetres, 1524 millimetres, 60 inches, and approximately 1.667 yards. The kilometre and mile equivalents (0.001524 km and 0.000947 mi) are also shown in the same panel.

## Frequently asked questions

### How does the converter handle categories with both metric and imperial units?

Every value is first converted to the base SI unit for that category (metre for length, kilogram for mass, litre for volume, square metre for area, metre per second for speed, byte for data). From that base value each target unit is calculated by dividing by its own exact conversion factor, so all results stay consistent with no accumulated rounding.

### Where do the conversion factors come from?

All factors are taken directly from NIST Special Publication 811 and the BIPM SI Brochure (9th edition). Inch-to-metre (1 in = 0.0254 m), pound-to-kilogram (1 lb = 0.45359237 kg), and gallon-to-litre (1 US gal = 3.785411784 L) are exact definitions, not rounded approximations. Binary data prefixes follow IEC 80000-13 (1 KiB = 1024 bytes).

### Why are some results shown with many decimal places?

When converting between units of very different magnitudes — say, miles to millimetres — the result naturally carries many significant figures to remain useful. You can round the displayed number to as many places as your task requires; the underlying calculation always uses the full-precision factor.

### What is the difference between KB and KiB for data sizes?

KB (kilobyte) follows the decimal SI convention: 1 KB = 1000 bytes, used by hard-drive manufacturers and network speeds. KiB (kibibyte) follows the binary IEC convention: 1 KiB = 1024 bytes, used by operating systems when reporting file or memory sizes. The same distinction applies to MB vs MiB, GB vs GiB, and TB vs TiB.

### Can I convert temperatures here?

Temperature is not in this converter because Celsius, Fahrenheit, and Kelvin use offset formulas (not simple multiplication), which require a separate approach. Use the Temperature Converter for those.

## Related calculators

- [Temperature Converter](https://youcalc.com/en/conversions-units/temperature-converter/)
- [Land Area Converter](https://youcalc.com/en/conversions-units/land-area-converter/)
- [Fuel Economy Converter](https://youcalc.com/en/conversions-units/fuel-economy-converter/)

## Sources

- https://www.nist.gov/pml/special-publication-811
- https://www.bipm.org/en/publications/si-brochure

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Interactive version: https://youcalc.com/en/conversions-units/unit-converter/ · From YouCalc — https://youcalc.com