Writing big and small numbers
Scientific notation writes a number as a value between 1 and 10 times a power of ten. The speed of light, 299,792,458 m/s, becomes 2.99792458 × 10⁸; the width of a bacterium, 0.000002 m, becomes 2 × 10⁻⁶. The exponent tells you the order of magnitude at a glance, and multiplying is easy: add the exponents.
E notation is the same thing for keyboards and spreadsheets: 6.022e23 means 6.022 × 10²³. Engineering notation keeps the exponent a multiple of 3, so it lines up with SI prefixes: 4.5 × 10⁻⁴ A is 450 × 10⁻⁶ A, that is 450 µA.
Significant figures
The number of digits in the mantissa shows how precise a value is. Rounded to 3 significant figures, the speed of light is 3.00 × 10⁸ m/s.
How this works
The page finds the exponent as the integer part of log₁₀ of the absolute value, divides the number by that power of ten, and rounds the result to the number of significant figures you choose; if rounding pushes the mantissa to 10, it shifts it back and raises the exponent. Engineering notation lowers the exponent to the nearest multiple of 3 and scales the mantissa to between 1 and 1,000. You can type plain numbers, numbers with comma thousands separators, or E notation. Everything runs in your browser.
Frequently asked
How do I write 0.00045 in scientific notation?
4.5 × 10⁻⁴: move the decimal point 4 places to the right, so the exponent is −4.
What does 1.5e6 mean?
1.5 × 10⁶ = 1,500,000. The e stands for times ten to the power.
What is engineering notation?
Scientific notation with exponents that are multiples of 3, matching kilo, mega, milli, micro and so on.
How many significant figures should I use?
As many as the measurement supports. Rounding to fewer digits hides false precision.
Sources
Reviewed Oct 17, 2026 · test vectors fixtures/calculators/math/scientific-notation-calculator/