What Are SI Prefixes?
SI prefixes (International System of Units prefixes) are symbols placed before a unit to indicate a power-of-10 multiple. Standardized by the General Conference on Weights and Measures (CGPM) in 1960, there are currently 20 official prefixes ranging from yotta (10²⁴) to yocto (10⁻²⁴). They allow scientists and engineers to express very large or very small quantities concisely.
Common SI Prefixes
| Prefix | Symbol | Value | Example |
|---|---|---|---|
| Tera | T | 10¹² | 1 TB = 1 trillion bytes |
| Giga | G | 10⁹ | 1 GHz = 1 billion Hz |
| Mega | M | 10⁶ | 1 MB = 1 million bytes |
| Kilo | k | 10³ | 1 km = 1,000 m |
| Milli | m | 10⁻³ | 1 mm = 0.001 m |
| Micro | μ | 10⁻⁶ | 1 μm = 0.000001 m |
| Nano | n | 10⁻⁹ | 1 nm = 1 billionth of a meter |
| Pico | p | 10⁻¹² | 1 pF = 1 trillionth of a farad |
How to Convert Between SI Prefixes
Subtract the target prefix exponent from the source prefix exponent to find the power-of-10 multiplier. For example, to convert 5 km to m: kilo is 10³, base unit is 10⁰, difference is 3, so 5 × 10³ = 5,000 m.
Frequently Asked Questions
1 kilo (k) equals 10³ = 1,000 base units. For example, 1 km = 1,000 m, and 1 kg = 1,000 g.
Micro (μ) is 10⁻⁶ (one millionth), and nano (n) is 10⁻⁹ (one billionth). So 1 μm = 1,000 nm.
Multiply the value by 10 raised to the difference in exponents. For example, 5 km to m: 5 × 10^(3-0) = 5,000 m.