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Round to 2 Significant Figures Calculator

Count the significant figures in any number with every digit classified by rule, or round a number to 1–15 significant figures with exact string-based math.

Processing... 0%
Parsing the number
Classifying every digit
Applying the sig-fig rules

Result

This page opens the sig fig calculator preset to round to 2 significant figures: enter any number and only its two leading significant digits survive, with the third digit deciding whether the second rounds up.

Two sig figs is a coarse precision used for quick estimates and error margins. 1234 becomes 1200, 0.04562 becomes 0.046, and 987 becomes 990 — in each case the first two significant digits are kept and the next digit is the judge: 5 or more rounds up, less than 5 rounds down. The math runs on the digit string you typed, not on a binary float, so borderline inputs never wobble.

Note that a result like 1200 no longer shows how precise it is — its trailing zeros are placeholders. The calculator says so under the answer and offers the scientific form 1.2 × 10³; tick the checkbox to get scientific notation directly. To round to a fixed number of decimal places instead, use the separate rounding calculator on this site.

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Executed in Browser

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Accepted Formats & Rules

  • Counter mode: per-digit classification — nonzero, captive zero, leading zero, trailing zero with or without a decimal point.
  • Rounding mode: 1 to 15 significant figures with digit-string math, so 0.0019997 becomes 0.00200 with its trailing zeros intact.
  • Optional scientific notation output, like 1.20 × 10³.
  • Honest notes for the tricky cases: the number zero and integers ending in zeros.

Key Benefits

✓ Every digit is highlighted and labelled with the exact rule that makes it significant or not — you learn the why, not just the count.
✓ Ambiguity is flagged honestly: trailing zeros in 1200 are called out as ambiguous, with the scientific notation that would resolve them.
✓ Runs entirely in your browser: no sign-up, no upload, instant results.

Use Cases

  • • Check chemistry and physics homework: count the sig figs in a measurement and see the rule behind every digit.
  • • Round lab results to 2, 3 or 4 significant figures with digit-exact math — 0.0019997 keeps its trailing zeros as 0.00200.
  • • Resolve ambiguous integers like 1200 by switching to scientific notation such as 1.200 × 10³.