SI Prefix Converter

SI prefixes are the shorthand the entire scientific world uses to avoid writing strings of zeros. Kilo-, mega-, giga-, tera- step up by factors of 1,000. Milli-, micro-, nano-, pico- step down by 1,000. Learning the ladder eliminates most arithmetic errors in technical reading.

The standard SI prefixes step by 1,000 from atto (10⁻¹⁸) to exa (10¹⁸), with zetta, yotta, ronna, quetta extending upward and zepto, yocto, ronto, quecto downward. Centi- and deci- (hundredth and tenth) are the odd retainers from earlier decimal notation; they persist in centimeter and decibel.

Each step is 1,000. Kilo to mega is ×1,000. Kilo to milli is ×10⁶ (six zeros). Reading a datasheet: 2.2 µF × 10⁻⁶ = 0.0000022 F. Writing the prefix saves digits.

• Yotta (Y, 10²⁴)
• Zetta (Z, 10²¹)
• Exa (E, 10¹⁸)
• Peta (P, 10¹⁵)
• Tera (T, 10¹²)
• Giga (G, 10⁹)
• Mega (M, 10⁶)
• Kilo (k, 10³)
• Hecto (h, 10²)
• Deka (da, 10¹)
• Base unit (10⁰)
• Deci (d, 10⁻¹)
• Centi (c, 10⁻²)
• Milli (m, 10⁻³)
• Micro (µ, 10⁻⁶)
• Nano (n, 10⁻⁹)
• Pico (p, 10⁻¹²)
• Femto (f, 10⁻¹⁵)
• Atto (a, 10⁻¹⁸)
• Zepto (z, 10⁻²¹)
• Yocto (y, 10⁻²⁴)

• Milli- vs micro-. 10⁻³ vs 10⁻⁶ — 1,000× different. Handwritten 'mA' can be confused with 'µA.' Always clarify.
• Centi- and deci- are not 1,000-step. Centi is 10⁻², deci is 10⁻¹. Non-standard for SI work.
• Binary vs decimal for data. Kilo = 1,000 in SI; kibi = 1,024 in binary. Related in KB vs KiB.

• 1 gigabyte = 10⁹ bytes = 1,000,000,000 bytes.
• 1 nanometer = 10⁻⁹ m = 0.000000001 m.
• 1 microsecond = 10⁻⁶ s = 0.000001 s.
• 1 terawatt = 10¹² W = 1,000,000,000,000 W.
• Age of universe: ~13.8 Gyr (gigayears) = 4.35 × 10¹⁷ s.
• Plank length: 1.6 × 10⁻³⁵ m (below quecto scale).

• Memorize the ladder: atto, femto, pico, nano, micro, milli, (unit), kilo, mega, giga, tera, peta, exa.
• Convert everything to scientific notation if the prefix ladder gets confusing.

Related: Data Storage Converter · Frequency Converter · Time Converter.