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Significant Figures Calculator

Round any number to a specified number of significant figures and view it in scientific notation.

Significant figures are the digits in a number that carry meaningful precision. This calculator rounds any number to however many sig figs you need and explains exactly why each digit counts or does not count. Useful for physics, chemistry, and any science where measurement precision matters.

Frequently Asked Questions

Significant figures (sig figs) are the digits in a number that contribute meaningful information about its precision. The number 1.234 has four sig figs. The number 1200 might have two, three, or four depending on context. Sig figs communicate how precisely a measurement was made.

They prevent false precision. If you measure something to the nearest millimetre and get 12.3mm, reporting it as 12.300mm implies far greater accuracy than you actually have. In science and engineering, using the wrong number of sig figs can misrepresent measurement quality and cause calculation errors downstream.

Enter your number and the calculator will identify and count all significant figures for you, highlighting which digits count and why. This is faster and less error-prone than applying the rules manually.

Decimal places count digits after the decimal point. Significant figures count all meaningful digits regardless of the decimal. The number 0.0045 has two sig figs but four decimal places. The number 1200 has four decimal places but potentially only two sig figs. They measure different things.

It depends on its position. Trailing zeros after a decimal point are always significant: 12.50 has four sig figs. Trailing zeros before a decimal point in a whole number are ambiguous: 1200 may have 2, 3, or 4 sig figs. Scientific notation removes this ambiguity.

Leading zeros are never significant: 0.004 has one sig fig. Trapped zeros (between non-zero digits) are always significant: 1004 has four sig figs. Trailing zeros after a decimal are significant: 3.00 has three sig figs. Trailing zeros in a whole number without a decimal are ambiguous.