Unit Converter
Measurement units are fundamental in science, engineering, commerce, and everyday life. They standardize the way we quantify and compare everything from lengths and weights to volumes and data sizes. Below is an overview of the most commonly used systems and scales for measurement:
International System of Units (SI)
The International System of Units (SI), or Metric System, is the most widely adopted measurement system globally. It’s used by scientists and many countries for consistency and ease of communication across international borders. The SI is based on a decimal system and includes seven base units:
- Meter (m) – for length
- Kilogram (kg) – for mass
- Second (s) – for time
- Ampere (A) – for electric current
- Kelvin (K) – for temperature
- Mole (mol) – for amount of substance
- Candela (cd) – for luminous intensity
These units can be modified by adding prefixes to represent different scales (e.g., milli-, centi-, kilo-, mega-), making them versatile for measuring everything from microscopic distances to astronomical ones.
The International System is a standard established and revised by BIPM (Bureau International des Poids et Mesures -International Bureau of Weights and Measures).
Imperial System
The Imperial System is primarily used in the United States and a few other countries. It includes units such as:
- Inches, Feet, and Yards – for length
- Pounds and Ounces – for weight
- Gallons and Pints – for volume
Unlike the SI, the Imperial System does not follow a base-10 structure, which can make conversions challenging. However, it remains widely used in certain applications, particularly in construction and industry in the U.S.
Scales and Prefixes
Scales and prefixes allow measurements to be represented in manageable quantities, regardless of their magnitude. Here are some standard prefixes:
| Prefix | Symbol | Factor | Power of 10 | Scale |
|---|---|---|---|---|
| Yotta | Y | 1,000,000,000,000,000,000,000 | 1024 | Septillion |
| Zetta | Z | 1,000,000,000,000,000,000 | 1021 | Sextillion |
| Exa | E | 1,000,000,000,000,000 | 1018 | Quintillion |
| Peta | P | 1,000,000,000,000 | 1015 | Quadrillion |
| Tera | T | 1,000,000,000,000 | 1012 | Trillion |
| Giga | G | 1,000,000,000 | 109 | Billion |
| Mega | M | 1,000,000 | 106 | Million |
| Kilo | k | 1,000 | 103 | Thousand |
| Hecto | h | 100 | 102 | Hundred |
| Deca | da | 10 | 101 | Ten |
| Base Unit | – | 1 | 100 | One |
| Deci | d | 0.1 | 10-1 | Tenth |
| Centi | c | 0.01 | 10-2 | Hundredth |
| Milli | m | 0.001 | 10-3 | Thousandth |
| Micro | µ | 0.000001 | 10-6 | Millionth |
| Nano | n | 0.000000001 | 10-9 | Billionth |
| Pico | p | 0.000000000001 | 10-12 | Trillionth |
| Femto | f | 0.000000000000001 | 10-15 | Quadrillionth |
| Atto | a | 0.000000000000000001 | 10-18 | Quintillionth |
| Zepto | z | 0.000000000000000000001 | 10-21 | Sextillionth |
| Yocto | y | 0.000000000000000000000001 | 10-24 | Septillionth |
Complete Table
| Unit | System | Symbol | in Feet | in Metres | Notes |
|---|---|---|---|---|---|
| Twip | Typographic | 1⁄17280 | 0.0000176389 | Typographic. | |
| Thou | Imperial | th | 1⁄12000 | 0.0000254 | |
| Barleycorn | Imperial | 1⁄36 | 0.0084667 | 1⁄3 in | |
| Inch | Imperial | in (″) | 1⁄12 | 0.0254 | 1 metre ≈ 39.3701 in |
| Hand | Imperial | hh | 1⁄3 | 0.1016 | Used to measure the height of horses |
| Foot | Imperial | ft (′) | 1 | 0.3048 | 12 in |
| Yard | Imperial | yd | 3 | 0.9144 | Defined as exactly 0.9144 m by the international yard and pound agreement of 1959 |
| Chain | Imperial | ch | 66 | 20.1168 | 100 links, 4 rods, or 1⁄10 of a furlong. The distance between the two wickets on a cricket pitch. |
| Furlong | Imperial | fur | 660 | 201.168 | 220 yd |
| Mile | Imperial | mi | 5280 | 1609.344 | 1760 yd or 80 chains |
| League | Old | lea | 15840 | 4828.032 | |
| Fathom | Maritime | ftm | 6.0761 | 1.852 | The British Admiralty in practice used a fathom of 6 ft. This was despite its being 1⁄1000 of a nautical mile (i.e. 6.08 ft) until the adoption of the international nautical mile. |
| Cable | Maritime | 607.61 | 185.2 | One tenth of a nautical mile. Equal to 100 fathoms under the strict definition. | |
| Nautical mile | Maritime | nmi | 6076.1 | 1852 | Used for measuring distances at sea (and also in aviation) and approximately equal to one arc minute of a great circle. |
| Metre (Meter) | SI | m | 0.3048 | 1 | |
| Kilometre (Kilometer) | SI | km | 304.8 | 1,000 | |
| Centimetre (Centimeter) | SI | cm | 0.003048 | 0.01 | |
| Millimetre (Millimeter) | SI | mm | 0.0003048 | 0.001 | |
| Light-year | Astronomical | ly | 2.88363E+15 | 9.46073E+15 | The distance that light travels in a vacuum in one Julian year. |
| Light-day | Astronomical | 7894950439542 | 25902068371200 | 24 light-hours | |
| Light-hour | Astronomical | 328956268314 | 1079252848800 | 60 light-minutes | |
| Light-minute | Astronomical | 5482604472 | 17987547480 | 60 light-seconds | |
| Light-second | Astronomical | 91376741.2 | 299792458 | Distance light travels in one second in vacuum. | |
| Parsec | Astronomical | pc | 9.40515E+15 | 30856775814913673 | |
| Astronomical Unit | Astronomical | au | 45597430989 | 149,597,870,700 | Earth-Sun distance (the average of Earth’s aphelion and perihelion). |
| Toise | Old | T | 0.5940662642 | 1.9490363 | 27000 / 13853 m |
| Cubit | Old | H | 0.1524 | 0.5 | Distance from fingers to elbow ≈ 18 in |
| Fermi | SI | fm | 0 | 0 | 1×10^−15 m |
| Shaku | Japan | 0.09236363544 | 0.3030303 | 10/33 m |
See also: Number Explorer