What are SI prefixes?

SI prefixes are multipliers attached to SI units to express very large or very small quantities compactly. They are defined as powers of 10: kilo (k) = 10³, mega (M) = 10⁶, milli (m) = 10⁻³, micro (μ) = 10⁻⁶, etc. They apply to any SI unit: km, MHz, mA, μF, nS, etc.

What are the 2022 CGPM additions?

In 2022, the 27th General Conference on Weights and Measures (CGPM) added four new prefixes to the SI: quetta (Q) = 10³⁰, ronna (R) = 10²⁷, ronto (r) = 10⁻²⁷, and quecto (q) = 10⁻³⁰. These were needed to express data storage (yottabytes were running out) and ultra-small quantities in quantum physics.

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Prefixes Converter

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Enter a quantity expressed in one SI prefix to convert it to any other prefix. For example: 1 kilo → millis shows 1,000,000.

From

Sig. figures:

Sci notation

Quetta (Q)

Q = 10⁺³⁰

1.000000e-27

Ronna (R)

R = 10⁺²⁷

1.000000e-24

Yotta (Y)

Y = 10⁺²⁴

1.000000e-21

Zetta (Z)

Z = 10⁺²¹

1.000000e-18

Exa (E)

E = 10⁺¹⁸

1.000000e-15

Peta (P)

P = 10⁺¹⁵

1.000000e-12

Tera (T)

T = 10⁺¹²

1.000000e-9

Giga (G)

G = 10⁺⁹

1.000000e-6

Mega (M)

M = 10⁺⁶

0.001

Kilo (k)

k = 10⁺³

1(input)

Hecto (h)

h = 10⁺²

Deca (da)

da = 10⁺¹

100

Base unit (×1)

- = 10⁺⁰

1000

Deci (d)

d = 10^-1

10000

Centi (c)

c = 10^-2

100000

Milli (m)

m = 10^-3

1.00000e+6

Micro (μ)

μ = 10^-6

1.000000e+9

Nano (n)

n = 10^-9

1.000000e+12

Pico (p)

p = 10^-12

1.000000e+15

Femto (f)

f = 10^-15

1.000000e+18

Atto (a)

a = 10^-18

1.000000e+21

Zepto (z)

z = 10^-21

1.000000e+24

Yocto (y)

y = 10^-24

1.000000e+27

Ronto (r)

r = 10^-27

1.000000e+30

Quecto (q)

q = 10^-30

1.000000e+33

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Convert between all 25 official SI metric prefixes. Includes the 2022 CGPM additions: quetta (Q, 10³⁰), ronna (R, 10²⁷), ronto (r, 10⁻²⁷), quecto (q, 10⁻³⁰). Enter a value in one prefix and see all 25 equivalents simultaneously. Examples: 1 km = 10⁶ mm = 10⁻³ Mm; 1 GHz = 10³ MHz = 10⁻³ THz. Scientific notation strongly recommended. 100% browser-based.

How to Use

1Read the intro note: enter a number expressed in one prefix to convert to all others
2Type a number in the input field (e.g. 1 for '1 kilo')
3Select your starting prefix from the From dropdown (e.g. Kilo, Mega, Nano)
4Select your target prefix from the To dropdown - the result appears instantly
5All 25 prefix conversions appear simultaneously across Large and Base/Small groups
6Enable Sci notation (recommended - values span 60 orders of magnitude)
7Hover any row to copy or use as input; click ⇄ to swap
8Open 'Common prefix examples' for practical examples like km, MHz, nm

Features

25 SI prefixes: quecto (10⁻³⁰) through quetta (10³⁰)
Includes 2022 CGPM additions: quetta, ronna, ronto, quecto
Groups: Large (×10ⁿ, n>0), Base & Small
Exponent shown next to each prefix label
Scientific notation on by default
One-click copy per result
100% browser-based

Prefixes Converter

How to Use

Features

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