What Are SI Prefixes? (kilo, milli, micro, nano, pico)
SI prefixes are multiplier symbols placed before units to write very large or very small values compactly. The most common in electronics are: kilo (k) = 10³, milli (m) = 10⁻³, micro (µ) = 10⁻⁶, nano (n) = 10⁻⁹, pico (p) = 10⁻¹². For example, 1 kΩ = 1000 Ω and 100 nF = 0.0000001 F. The right prefix makes reading and calculation easier.
SI prefixes are multiplier names that let us write very large or very small numbers simply. You meet them constantly in electronics: kΩ (kilohm), µF (microfarad), mA (milliampere), MHz (megahertz).
What Is an SI Prefix?
A prefix goes in front of the unit and multiplies it by a power of 10. For example, "kilo" multiplies by 1000, and "milli" by 0.001. So instead of 1000 Ω we can write 1 kΩ.
Prefix Table
| Prefix | Symbol | Multiplier |
|---|---|---|
| Giga | G | 1,000,000,000 |
| Mega | M | 1,000,000 |
| Kilo | k | 1,000 |
| (unit) | — | 1 |
| Milli | m | 0.001 |
| Micro | µ | 0.000001 |
| Nano | n | 0.000000001 |
| Pico | p | 0.000000000001 |
Common Use in Electronics
Resistance is usually in Ω/kΩ/MΩ; a capacitor in µF/nF/pF; current in A/mA/µA; frequency in Hz/kHz/MHz.
Conversion Example
1 µF = 1,000 nF = 1,000,000 pF. Likewise 2,200 Ω = 2.2 kΩ and 0.1 A = 100 mA. Converting everything to the base unit before calculating prevents errors.
Common Mistakes
- Calculating without the prefixes: putting mA into a formula without converting to A throws the result off by 1000×.
- Confusing µ and m: micro (µ) and milli (m) differ by a factor of a thousand.
- Upper/lower case: M (mega) and m (milli) are very different; the letter case matters.
Frequently Asked Questions
What are the most-used SI prefixes in electronics?+
How many ohms is 1 kΩ?+
How many farads is 100 nF?+
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