Scientific notation converter
Convert between plain numbers, scientific notation (mantissa × 10^exponent) and engineering notation (exponent a multiple of 3), with a configurable number of significant digits plus mantissa, exponent, integer and precision details.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Convert between plain, scientific (mantissa × 10^exponent) and engineering notation (exponent a multiple of 3).
Result
What this tool does
- Turn a long number from a paper, an API response or a log into scientific notation so you stop miscounting zeros.
- Engineering notation keeps the exponent a multiple of 3, which lines up with the k / M / G prefixes and reads far better for capacitance, resistance or frequency values.
- Run it backwards: take 1.2345e-8 and convert it to a plain number to see how many decimal places that really is.
- Check floating point precision: an integer beyond Number.MAX_SAFE_INTEGER already has unreliable trailing digits and the tool flags it.
Example
Input
123456789
Output
1.23456789e+8 (scientific); 123.456789e+6 (engineering); 123456789 (plain); 123,456,789 (grouped)
With the default "auto" significant digits nothing is truncated, so the mantissa is 1.23456789 with exponent 8. For 0.00042 you get 4.2e-4 and 420e-6.
Frequently asked questions
How do scientific and engineering notation differ?
Scientific notation keeps the mantissa in [1, 10) and lets the exponent be anything; engineering notation forces the exponent to a multiple of 3 with the mantissa in [1, 1000). The same number 123456789 is 1.23456789e+8 or 123.456789e+6 respectively, and the engineering form maps directly onto the k / M / G prefixes.
Why does the plain number come back in e-notation sometimes?
When the absolute value is ≥ 1e21 or < 1e-6, JavaScript’s own String(number) already prints scientific notation. The tool follows the same rule and notes that the value is outside the readable plain range.
What should I put in significant digits?
Leave it empty to keep the shortest untruncated form. An integer from 1 to 15 rounds to that many significant digits — with 3, 123456789 becomes 1.23e+8, 123e+6 and 123000000. Values above 15 are rejected because an IEEE 754 double reliably carries at most 15 significant decimal digits.
Can I paste grouped, hex or full-width input?
Yes. 1,234.5 (US style), 1.234,5 (European style), 1_234, 0x1f, 0b1010 and 0o17 all parse, and a Unicode minus sign (−) counts as negative. Anything else answers "not a valid number".
Is my input uploaded?
No. Parsing and conversion run entirely in the browser in plain JavaScript — no network requests, no logging of what you typed.
Keywords：scientific notationengineering notationexponentmantissasignificant digits科学计数法工程计数法指数尾数有效数字e 记法