BYTETOOLS

Significant Figures Calculator

Count the significant figures in any number and round values to a chosen number of sig figs, with the counting rules explained for each answer.

Count significant figures

3
Significant figures
Counted / none
Trailing zeros

Why

Leading zeros are placeholders and never significant; all 3 digits from the first non-zero digit count (trailing zeros count because a decimal point is present).

Round to significant figures

Rounded result

Plain: 98800

Scientific: 9.88e+4

What is the Significant Figures Calculator?

The ByteTools Significant Figures Calculator does two jobs: it counts the significant figures in a number exactly as you typed it, and it rounds any value to a chosen number of significant figures.

  • Counts sig figs from the written form, so trailing zeros are respected
  • Explains which counting rule applied to your number
  • Flags ambiguous trailing zeros in whole numbers
  • Rounds any value to 1–15 significant figures
  • Scientific notation supported for input and output
  • 100% private — runs entirely in your browser

How to use the Significant Figures Calculator

  1. 1

    Type the number exactly as written, e.g. 0.00520 or 1.20e3.

  2. 2

    Read the significant-figure count and the rule that applied.

  3. 3

    To round, enter a value and the number of significant figures to keep.

  4. 4

    Read the rounded result in plain and scientific notation.

  5. 5

    Copy either result with one click.

About the Significant Figures Calculator

The ByteTools Significant Figures Calculator does two jobs: it counts the significant figures in a number exactly as you typed it, and it rounds any value to a chosen number of significant figures. For every count it explains which rule applied — why leading zeros never count, and when trailing zeros do.

Because trailing zeros matter, the counter reads your number as written text rather than as a computed value: 0.00520 has three significant figures, 1200 has two by convention, and 1.20e3 has three. Scientific notation is fully supported, which is also the standard way to make trailing zeros unambiguous.

The rounding mode handles the exponent correctly, so 98,765 rounded to 3 sig figs becomes 98,800 (not 98.8), and tiny values like 0.012345 round to 0.0123. Everything runs locally in your browser — nothing is uploaded, and it works offline.

Frequently asked questions

What are significant figures?

Significant figures are the digits in a number that carry meaningful precision: all non-zero digits, zeros between them, and trailing zeros after a decimal point. They tell you how precisely a value was measured — 2.50 cm claims more precision than 2.5 cm.

How many significant figures does 0.00520 have?

Three: the 5, the 2, and the final 0. The leading zeros are only placeholders that set the decimal scale, so they never count. The trailing zero counts because it comes after the decimal point — writing it signals that the measurement is precise to that place.

Are trailing zeros in 1200 significant?

It is ambiguous. By the usual convention, 1200 has two significant figures because bare trailing zeros in a whole number are treated as placeholders. To show four sig figs, write 1200. with a decimal point, or 1.200 × 10³ in scientific notation.

How do you round to 3 significant figures?

Keep the first three significant digits and round the third based on the digit after it, preserving the number's magnitude with zeros. So 98,765 becomes 98,800 and 0.012345 becomes 0.0123. The calculator handles the exponent so the size of the number never changes.

Why use significant figures instead of decimal places?

Decimal places measure position, while significant figures measure relative precision, which is what science cares about. A measurement of 0.003 g to 3 decimal places has just one sig fig — quoting more digits in a result than your least precise measurement would overstate your accuracy.

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