What this calculator does
Switch a measurement from one metric prefix to another, like microfarads to nanofarads, without slipping a decimal place. Metric prefixes are short names for powers of ten. Kilo means a thousand, milli a thousandth, micro a millionth, and so on. They attach to any SI (metric) unit: kilometers, milligrams, microfarads, gigahertz. Changing from one prefix to another never changes the amount itself. It only moves the decimal point.
This converter moves a value between any two of the 25 SI prefixes. That includes ronna, quetta, ronto and quecto, which were added in 2022. It shifts the decimal point exactly, instead of using the computer's usual rounded math. So 0.3 mF becomes exactly 300 µF. Pick a unit to label the answer, or leave it as a bare prefix.
Where it's used
Why this math matters outside the classroom:
- Electronics parts. Hobbyists rewrite a 0.1 µF capacitor as 100 nF to match the code printed on the part.
- Science class. Students convert 2,500 mm to 2.5 m by moving the decimal point three places left.
- Radio frequencies. A radio listener converts 101.1 MHz to 0.1011 GHz, or 101,100 kHz, to compare tuning ranges.
- Medicine labels. Pharmacy students see that 500 mg is 0.5 g and 500,000 µg by shifting three places at a time.
- Light wavelengths. A physics student writes 550 nm green light as 0.55 µm or 5.5 × 10⁻⁷ m.
Grade level and standards: Grades 5–6; Common Core State Standards for Mathematics 5.MD.A.1, 5.NBT.A.2. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter the value. Negative numbers and decimals are fine.
- Choose the prefix the value has now and the prefix you want.
- If you like, choose the unit, such as m, g, Hz or F, so the answer is labeled. The math is the same for every unit.
- Read the converted value, its scientific notation, and the table of the same value with every nearby prefix.
What the inputs mean
- Value
- Any number, including decimals and negatives.
- From prefix
- The prefix symbols are case-sensitive. M is mega (a million) and m is milli (a thousandth). P is peta and p is pico.
- Unit (optional)
- Prefixes for bytes and bits here are the decimal ones (1 kB = 1,000 B). The binary units KiB, MiB and GiB (powers of 1,024) are a separate system.
Formula and method
result = value × 10^(from exponent − to exponent) kilo = 10³, mega = 10⁶, giga = 10⁹, tera = 10¹² milli = 10⁻³, micro = 10⁻⁶, nano = 10⁻⁹, pico = 10⁻¹²
Every prefix stands for a power of ten, and its exponent is the small raised number. For example, kilo is 10³, a 1 followed by three zeros. To convert, subtract the exponent of the prefix you want from the exponent of the prefix you have.
A positive difference moves the decimal point that many places to the right. The number gets bigger, because the new unit is smaller. A negative difference moves it to the left.
Prefixes from kilo up, and from milli down, go in steps of three powers of ten. The four in the middle fill the gap: hecto (10²), deca (10¹), deci (10⁻¹) and centi (10⁻²). They're mostly used with meters, liters and grams.
Worked example
A circuit diagram calls for a 0.047 µF capacitor, but the parts list is in nanofarads. What value is that?
- Micro is 10⁻⁶ and nano is 10⁻⁹.
- The shift is −6 − (−9) = 3, so move the decimal point 3 places to the right.
- 0.047 µF × 10³ = 47 nF.
Result: 0.047 µF is 47 nF, the same capacitor written with a different prefix.
Understanding the result
Going to a smaller prefix gives a bigger number, and going to a larger prefix gives a smaller number. That's because the amount itself never changes.
Engineers usually pick the prefix that leaves a number between 1 and 1,000. For example, 47 nF rather than 0.047 µF or 47,000 pF. That's the idea behind engineering notation.
Assumptions and limitations
- Prefixes are the SI decimal prefixes set by the BIPM, the international measurement bureau. Each is an exact power of ten.
- The value and its prefix apply to the whole unit, not to a squared or cubed unit.
- For area and volume units, the prefix is squared or cubed along with the unit: 1 km² is 10⁶ m², not 10³ m². This converter handles plain units only.
- Binary prefixes (Ki, Mi, Gi) aren't included. Use a data storage converter for those.
- It doesn't change units, only prefixes: meters stay meters.
Frequently asked questions
How many nanometers are in a micrometer?
1,000. Micro is 10⁻⁶ and nano is 10⁻⁹, a difference of three powers of ten. So 1 µm = 1,000 nm.
What are the newest SI prefixes?
In 2022 the General Conference on Weights and Measures added ronna (R, 10²⁷), quetta (Q, 10³⁰), ronto (r, 10⁻²⁷) and quecto (q, 10⁻³⁰). They're mainly for very large amounts of data and very small masses.
Why is the kilogram the base unit if kilo is a prefix?
For historical reasons, the SI base unit of mass already carries a prefix. Prefixes for mass are attached to the gram. So a thousandth of a kilogram is a gram, not a millikilogram.
Is a kilobyte 1,000 or 1,024 bytes?
With SI prefixes, a kilobyte is 1,000 bytes. 1,024 bytes is a kibibyte (KiB). Some software still uses kB loosely for 1,024, so check which one a figure means.
How this calculator is checked
Method: SI prefixes from the BIPM SI Brochure (9th edition) and the 2022 CGPM resolution adding ronna, quetta, ronto and quecto; each prefix is an exact power of ten. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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