What counts as significant
Significant figures are the digits that carry meaning. Leading zeros never count, so 0.004567 has four significant figures.
Trailing zeros in a whole number do not count either, so 1200 has two. Writing 1200.0 would make five.
Worked example
0.004567 to two significant figures is 0.0046, because the third significant digit is 6 and rounds the 5 up.
The same number in standard form is 4.6 x 10 to the power of -3.
Why significant figures matter
A measurement cannot be more precise than the instrument that took it. Reporting 0.004567 from a ruler marked in millimetres overstates what you know.
Rounding to significant figures keeps the answer honest and matches how the input was measured.
Inputs for the significant figures calculator
Number
The number to round. Leading zeros are ignored when counting significant figures.
Significant figures
How many meaningful digits to keep, from 1 to 15.
CALCULATOR QUESTIONS
Significant figures calculator questions
How many significant figures does 0.004567 have?
Four. The leading zeros only place the decimal point and do not count.
How do I round to 2 significant figures?
Keep the first two meaningful digits and round on the third. 0.004567 becomes 0.0046.
Do trailing zeros count?
In a whole number such as 1200 they do not, which is why standard form is clearer: 1.2 x 10 to the power of 3.
What is the difference from decimal places?
Decimal places count digits after the point. Significant figures count meaningful digits from the first non-zero digit.