Significant Figures
The digits in a measured or calculated quantity that carry meaningful contribution to its measurement precision.
SI unit
Dimensionless
In depth
Significant figures reflect instrument precision. Rules govern arithmetic: addition/subtraction results match the fewest decimal places of any input, while multiplication/division results match the fewest total significant figures.
Examples in the real world
Measuring 12.30 cm indicates four significant figures (uncertainty in the hundredths place), whereas 0.0012 kg has only two significant figures.