How to use the metric prefix converter
- Type the number. Plain numbers such as 2.5 or 0.004 work, and so does a form like 1.5e3.
- Choose the prefix the number has now under From prefix. Pick (no prefix) if it is in base units like meters, grams or watts.
- Choose the prefix you want under To prefix.
- Read the exact result and the table that shows the same quantity with every prefix. Copy, Print or export the CSV.
Formula
shift = exponent of the From prefix - exponent of the To prefix
result = number x 10^shift
kilo = 10^3, mega = 10^6, giga = 10^9, milli = 10^-3, micro = 10^-6
The result is an exact decimal shift of the digits you typed, so no rounding is involved. Very long results switch to scientific notation. The prefixes run from quecto (10^-30) to quetta (10^30), including ronna and ronto added in 2022.
2.5 giga to mega
Giga is 10^9 and mega is 10^6, so the exponent difference is 9 - 6 = 3. Moving the decimal point three places right turns 2.5 into 2,500, so 2.5 giga equals 2500 mega.
Going down, 0.004 milli (10^-3) to micro (10^-6) multiplies by 1,000 and gives 4 micro. A quantity of 1 kilo is 1,000 base units, 1,000,000 milli and 1,000,000,000 micro.
How prefixes work
A metric prefix is a power of ten that is written in front of a unit name: a kilometer is 1,000 meters and a millisecond is a thousandth of a second. Because every prefix is a power of ten, converting between them is only a matter of moving the decimal point by the difference in exponents. That is why no rounding error can creep in here.
The steps shown with your result spell out which exponents were used, which is useful when you want to check the work by hand.
Common mix-ups
Capital M is mega (a million) and lowercase m is milli (a thousandth), a difference of nine powers of ten. The symbol for micro is the Greek letter mu, often written u when it is not available. For computer storage, prefixes used in decimal mean powers of 1,000, while binary prefixes such as kibi and mebi mean powers of 1,024 and are not covered here. Use the storage unit size calculator for that.
For numbers that are very large or small, the scientific notation converter is a good companion, and the unit converter changes between different units of the same kind.
Assumptions and limits
- The number can have up to 60 digits and an exponent of up to four digits. Commas are ignored.
- The prefixes are the standard SI set from quecto to quetta. Binary prefixes are not included.
- Results longer than 24 characters are shown in scientific notation so they stay readable.
- Nothing is stored or uploaded.
Frequently asked questions
How do I convert giga to mega?
Giga is a thousand times larger than mega, so multiply by 1,000. Two and a half giga is 2,500 mega. The page does this by moving the decimal point.
What is the difference between milli and micro?
Milli is one thousandth and micro is one millionth, so one milli equals 1,000 micro. They are written m and the Greek letter mu.
Are the results rounded?
No. Prefix conversion is an exact shift of the decimal point, so the digits you type are the digits you get, just moved. Long results are shown in scientific notation for readability, not rounding.
Does this cover kibibytes and mebibytes?
No. Those binary prefixes are powers of 1,024 and are different from the powers of 1,000 used here. The storage unit size calculator on this site handles them.