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Significant Figures

Count a number's significant figures — with the why — and round to any precision.

Why this exists

Capacity math and engineering reports care about claimed precision: 1.20 promises more than 1.2. This shows which digits of a number are significant and the rule that makes each one count, then rounds values to the precision you actually measured.

🔒 Runs in your browser — nothing is sent anywhere
0.00120
3 significant figures
= 1.20 × 10^-3
  • Leading zeros only locate the decimal point — never significant.
  • Trailing zeros after a decimal point ARE significant — they claim measured precision.
0.00120