This rounding calculator rounds any number three ways — to a chosen number of decimal places, to significant figures, or to the nearest 10, 100 or 1,000 — using standard half-up rounding.

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The Rounding Rules (All of Them)

  • Find the digit in the rounding position. Look at the digit after it: 0–4, round down (keep); 5–9, round up. That is the whole game — everything else is choosing the position.
  • Decimal places count digits after the point (money: 2). Significant figures count meaningful digits from the first non-zero (science's choice, and the subject of our dedicated Significant Figures Calculator). Place value (nearest 100) counts from the left of the point.
  • This calculator uses half-up (school) rounding: exactly-half values go up. Banker's rounding (half-to-even, used to avoid bias in statistics) differs only at exact halves — 2.5 → 2 there, 3 here.

Part of our Math Calculators collection.

Worked Examples (Verified)

  • 3.14159 to 2 decimal places → 3.14 (third decimal is 1, down)
  • 4.567 to 2 significant figures → 4.6
  • 1,275 to the nearest 100 → 1,300 (the 7 in the tens place pushes up); 1,249 → 1,200
  • 0.125 to 2 dp → 0.13 under half-up (banker's would say 0.12 — know which game you are playing)

Rounding Traps

  • Never round twice: 2.449 → 2.45 (1 step to 2dp). Chaining 2.449 → 2.45 → 2.5 double-counts the push. Always round from the original number.
  • Round at the end of a calculation, not mid-stream — early rounding compounds into visibly wrong finals (the difference between a bridge budget and a bridge).
  • Trailing zeros carry information in science: 3.10 (3 sig figs, a measurement claim) is not the same statement as 3.1.

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Frequently Asked Questions

How do you round to 2 decimal places?

Keep two digits after the point; the third digit decides: 5 or more rounds the second digit up. 3.14159 → 3.14; 3.145 → 3.15 (half-up).

What does "round to significant figures" mean?

Keep a set count of meaningful digits starting from the first non-zero digit, regardless of where the decimal point sits: 0.004567 to 2 s.f. is 0.0046; 45,670 to 2 s.f. is 46,000.

What is the difference between half-up and banker's rounding?

Only the treatment of exact halves: half-up always goes up (2.5→3); banker's goes to the nearest even number (2.5→2, 3.5→4) to cancel systematic bias across many roundings. Schools teach half-up; statistics and computing quietly use banker's.

Why do computers sometimes round 2.675 to 2.67?

Binary floating-point cannot store 2.675 exactly — it is really 2.67499999…, so naive code rounds it down. This calculator nudges for that representation error; precision-critical work uses decimal arithmetic libraries.

Should I round measurements before or after calculating?

After. Carry full precision through the calculation and round only the final reported value — to the precision your least-precise measurement justifies.

Is this rounding calculator free?

Yes — free, instant, no sign-up.