Significant Figures
Count, identify, and round to significant figures with digit-by-digit highlighting
0.004200 → 4 sig figs | rounded to 3: 0.00420
Identified sig figs
4
Rounded result
0.00420
Rules applied
- • Non-zero digits are always significant
- • Leading zeros are not significant
- • Zeros between sig figs are significant
- • Trailing zeros after decimal point are significant
About this calculator
The Significant Figures Calculator counts the sig figs in any number and rounds it to your chosen precision, showing which digits are significant and which rules apply. Enter a measurement or calculation result to identify leading zeros, captive zeros, and trailing decimals correctly. Essential for chemistry, physics, and engineering lab work.
Common examples
- 1234 rounded to 2 sig figs → 1200 (sig figs: 1, 2)
- 0.00456 has 3 sig figs (4, 5, 6) — leading zeros are not significant
- 98765 rounded to 3 sig figs → 98800
- 0.02030 has 4 sig figs (2, 0, 3, 0) — trailing zero after decimal is significant
- 500.0 has 4 sig figs — decimal point makes all trailing zeros significant