Rounding Calculator
Round any number to a chosen number of decimal places, significant figures, or the nearest integer, 10, 100, or 1000.
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How to use this calculator
Standard rounding (half-up) rounds 0.5 and above to the next digit. Significant figures count from the first non-zero digit regardless of the decimal point position.
- 1
Enter the number you want to round.
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Select the rounding method from the dropdown (decimal places, significant figures, or nearest power of 10).
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The rounded value and rounding error are shown immediately.
Frequently asked questions
What is the difference between decimal places and significant figures?
Decimal places count digits after the decimal point: 3.14159 rounded to 2 dp = 3.14. Significant figures count all meaningful digits starting from the first non-zero digit: 3.14159 rounded to 3 sf = 3.14; but 0.00456 rounded to 2 sf = 0.0046 (the leading zeros are not significant).
What is "half-up" rounding?
In half-up rounding, digits 5–9 round up and digits 0–4 round down. So 2.5 → 3, and 2.45 → 2.5 → 3 (when rounding to 1 dp). Other methods include "half-even" (banker's rounding, which rounds 0.5 to the nearest even number), used in financial calculations to reduce systematic bias.
How do I round to the nearest 10, 100, or 1000?
Divide by the target (10, 100, or 1000), round to the nearest integer, then multiply back. For 1,357 to the nearest 100: 1357/100 = 13.57 → round to 14 → 14 × 100 = 1400. This calculator does this automatically.
Why do scientific measurements use significant figures instead of decimal places?
Significant figures convey the precision of a measurement regardless of the magnitude. A measurement of 0.0034 km and 3.4 m both have 2 significant figures — the same precision expressed in different units. Decimal places would differ (4 dp vs 1 dp), misleadingly suggesting different precision.
Rounding calculator — decimal places, significant figures, nearest 10/100/1000
Decimal places vs. significant figures
Decimal places measure distance from the decimal point: rounding to 2 dp always gives two digits after the dot. Significant figures measure meaningful precision: the result has a fixed number of non-trivial digits. For large numbers (e.g., 12,345.678) rounding to 3 sf gives 12,300 — much less precise than 3 dp (12,345.678 → 12,345.678). Use dp when comparing numbers on the same scale; use sf when comparing measurements of very different magnitudes.
Rounding in financial calculations
Finance uses "banker's rounding" (round half to even) to minimize cumulative bias across many transactions. For example, 0.5 rounds to 0 (nearest even), and 1.5 rounds to 2. Standard half-up rounding accumulates a slight positive bias over many operations, which matters for large-scale financial aggregation. Tax calculations and accounting standards often specify which rounding method is mandated.
Rounding errors and numerical stability
Every rounding operation introduces a small error. When rounded numbers are used in further calculations, errors can accumulate — a phenomenon called round-off error. Subtraction of nearly equal numbers amplifies relative error catastrophically (catastrophic cancellation). Numerical analysts design algorithms to minimize rounding error propagation, especially in scientific computing and engineering simulation software.
Learn more from an authoritative source:
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →