What is engineering notation versus scientific notation?

Engineering notation restricts the exponent to multiples of three so it lines up with SI prefixes. 47000 is written as 47e3 (47 kilo) rather than 4.7e4. Every metric prefix corresponds to one engineering-notation step of 1000.

Why do prefixes step by powers of 1000?

From kilo upward and milli downward, each prefix is a factor of 1000 from the next, which keeps the mantissa between 1 and 999. Centi, deci, deca, and hecto are the historical exceptions that step by 10.

What are the newest SI prefixes?

In 2022 the CGPM added ronna (1e27), quetta (1e30), ronto (1e-27), and quecto (1e-30) to cover data and physics scales. They are the largest and smallest official prefixes.

How does the converter rescale a value?

It multiplies your number by ten raised to the difference between the source exponent and the target exponent. Converting 5 mega to kilo multiplies by 10^(6-3) = 1000, giving 5000 kilo.

Are prefix symbols case sensitive?

Yes. Capital M is mega and lowercase m is milli, a factor of 10^9 apart. Capitals are used for prefixes of a million and above (except kilo), so getting the case wrong is a serious error.

Engineering Unit Prefix Reference

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SI prefixes let you write very large and very small quantities compactly by attaching a single letter to a unit. This reference lists every official prefix alongside its symbol, power of ten, and full numeric multiplier, and includes a converter to rescale a value from one prefix to another.

How it works

Each prefix represents a fixed power of ten. From kilo (10^3) upward and milli (10^-3) downward the steps are powers of one thousand, which is why they map cleanly onto engineering notation — notation where the exponent is always a multiple of three. The four small exceptions near unity (deca 10^1, hecto 10^2, deci 10^-1, centi 10^-2) step by ten instead.

To convert a value between two prefixes the tool simply applies the difference of their exponents:

result = value * 10^(sourceExponent - targetExponent)

So 2.5 giga in mega is 2.5 * 10^(9 - 6) = 2500 mega. No unit information is needed because both endpoints share the same base unit.

Tips and notes

Capitalisation is meaningful: M (mega, 10^6) and m (milli, 10^-3) differ by a factor of a billion. Always preserve case.
Prefixes do not stack: there is no such thing as a millikilometre — write it as a metre.
The 2022 additions ronna, quetta, ronto, and quecto extend the range to ±10^30, mainly for data storage and astrophysics.
Engineering notation keeps the mantissa in the 1–999 range, which is why it pairs naturally with these prefixes in spec sheets and calculators.