Leading zeros do not count
The nonzero value 0.004560 contains four significant figures: 4, 5, 6, and the final zero. Rounded to three figures it is 4.56 × 10^-3.
Count and round significant figures
For example, 1200 has 2 figures by default or 4 when checked. A decimal point or explicit e notation makes written trailing zeros significant. For zero, 0 has 1 figure and 0.00 has 2 by this tool’s convention.
Results
Significant figures in the input
4
Rounded to 3 significant figure(s)
4.56 × 10^-3
Ordinary decimal
0.00456
Scientific notation explicitly shows the requested digit count. An ordinary whole number ending in zeros may hide that count.
Calculations and exports run locally in your browser. Your entries are not sent to a calculation service.
How to use the Significant Figures Calculator
- 01
Enter the number exactly as written, including any decimal point and trailing zeros.
- 02
Choose whether trailing zeros in a plain whole number count as significant, then choose a target from 1 to 100 figures.
- 03
Select the halfway rule and read the scientific result. Added zeros format the number; they do not create measurement accuracy.
Examples
Ambiguous whole-number zeros
1200 has two significant figures under the default convention and four when the whole-number-zero option is checked. Writing 1.200e3 makes all four explicit.
Rounding can move the exponent
Rounding 999 to two significant figures gives 1.0 × 10^3. The extra zero after the decimal point records the second retained figure.
Count the written representation
For a nonzero number, leading zeros are placeholders; zeros between nonzero digits count. Written trailing zeros after a decimal point count too. This tool treats written zeros in explicit e notation as significant and offers a separate choice for plain whole numbers without a decimal point.
Zeros and exact counts need context
The precision of a measured zero is better described by its decimal resolution or uncertainty. For display, this tool counts 0 as one figure and a zero decimal by its digits after the decimal point, with a minimum of one. An exact count such as three objects has no measurement-limited figure count; the tool still analyzes its written digits.
Rounding is separate from uncertainty
A target figure count controls the output representation. It does not derive uncertainty, propagate errors through a calculation, or apply separate rules for addition and multiplication. Keep full working values and choose the final reporting precision appropriate to the task.
What to know
- Zero-valued inputs use the explicit display convention described above; scientific fields may adopt a different convention.
- No uncertainty propagation or significant-figure arithmetic expressions.
Common questions
Why are there two halfway rules?
Both are common explicit conventions. Ties to even avoids always increasing magnitude at exact halfway points; ties away from zero increases magnitude. The tool defaults to ties to even.
Can I request more figures than the input has?
Yes. Zeros are padded and a note appears. The extra digits are a formatting request, not evidence of additional measured precision.
Why prefer the scientific output for 1000?
The plain integer does not clearly distinguish 1, 2, 3, or 4 significant figures. Scientific forms such as 1e3 and 1.000e3 make the distinction visible.