Metric Prefix Converter

How it works

An SI prefix is a power of ten attached to a unit: kilo is 10^3, so 4.7 kΩ is 4.7 × 10^3 Ω = 4,700 Ω. Changing prefix changes only the power of ten, so the conversion is a single shift of the decimal point by the difference between the two exponents. From kilo (10^3) to milli (10^-3) the difference is 6, so 1 km is 10^6 mm.

The calculator works on the digits you typed rather than multiplying doubles, so the answer is exact however far apart the prefixes are: 1 Qg (quetta, 10^30) is 10^60 qg (quecto, 10^-30), written as a 1 followed by sixty zeros. The result is shown in standard notation and in scientific notation, and the factor line states the power of ten used.

The unit symbol you type only labels the result; the arithmetic is the same for Ω, F, m, g, B or Hz. The table lists your value against all 24 SI prefixes of the SI Brochure, 9th edition (2019), as amended in 2022, from quecto to quetta, plus the bare unit, so you can read off whichever form a datasheet or a lab report uses.

Formula

result = value × 10^(exponent(from) − exponent(to))
Q 10^30  R 10^27  Y 10^24  Z 10^21  E 10^18  P 10^15  T 10^12  G 10^9  M 10^6  k 10^3
h 10^2   da 10^1  (none) 10^0  d 10^-1  c 10^-2
m 10^-3  µ 10^-6  n 10^-9  p 10^-12  f 10^-15  a 10^-18  z 10^-21  y 10^-24  r 10^-27  q 10^-30

Example

A 4.7 kΩ resistor, the default: kilo is 10^3 and the bare ohm is 10^0, so the shift is 3 places and 4.7 kΩ = 4700 Ω, or 4.7 × 10^3 Ω. The factor line reads 1 kΩ = 10^3 Ω.

A 250 µF capacitor in nanofarads: micro is 10^-6 and nano is 10^-9, a difference of 3, so 250 µF = 250000 nF (2.5 × 10^5 nF). Going the other way, a 2.4 GHz Wi-Fi signal is 2.4 × 10^9 Hz = 2400000000 Hz, and 1 km is 1000000 mm.

Assumptions and limitations

• The prefixes are the 24 of the SI Brochure, 9th edition (BIPM), including ronna (R, 10^27), quetta (Q, 10^30), ronto (r, 10^-27) and quecto (q, 10^-30), which the 27th General Conference on Weights and Measures adopted in November 2022.
• The unit symbol is a label only. The calculator does not check that the prefix is sensible for the unit: SI does not allow compound prefixes (no "kµm"), and the kilogram is the one base unit that already carries a prefix, so prefixes attach to the gram (1 Mg, not 1 kkg).
• Binary prefixes (Ki, Mi, Gi) are powers of 1024, not of ten, and are not SI; 1 KiB is 1024 B while 1 kB is 1000 B. Use the data size converter for those.
• Results are exact because the digits are shifted rather than multiplied, so the standard form of an extreme conversion can run to sixty or more digits.

Frequently asked questions