How to use it
Enter the measured number as written, including a decimal point or scientific notation when those zeros are meaningful. Choose Count or Round; for rounding, choose 1–15 figures.
Method and worked example
Leading zeros are placeholders. Zeros between nonzero digits are significant. Trailing zeros after a decimal point are significant. In a whole number without a decimal point, trailing zeros are treated as ambiguous and not counted; use a decimal point or scientific notation to state intended precision. Rounding uses decimal digits with a half-up next-digit rule and displays normalized scientific notation.
Example
0.004500 has four significant figures. Rounding 9.99 to two significant figures gives 1.0e+1.
Assumptions and limitations
This tool does not evaluate arithmetic expressions or apply addition/subtraction versus multiplication/division propagation rules. The treatment of an integer such as 1200 is a stated convention, not a claim about the measurement instrument.
Privacy and accessibility
Calculations run in this browser session. This page does not send, store, or add your entered values to a URL. Controls work with a keyboard and results and errors are announced as text.