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

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