What are the rules of rounding?

The standard rule is 'half up': if the digit after the rounding place is 5 or more, round up. If it is 4 or less, round down. Ceiling always rounds towards positive infinity, while floor always rounds towards negative infinity.

What is the difference between decimal places and significant figures?

Decimal places count digits to the right of the decimal point (e.g. 0.0034 has 4 decimal places). Significant figures count all meaningful digits starting from the first non-zero digit (e.g. 0.0034 has 2 significant figures: 3 and 4).

Can you round to negative decimal places?

Yes. Rounding to -1 decimal places rounds to the nearest ten (e.g. 15 -> 20). Rounding to -2 rounds to the nearest hundred, and so on.

Rounding Calculator — round numbers, decimals, sig figs

Round a Number

Number to Round The input value you want to round. Can be a decimal or negative.

Rounding Mode Choose whether to count digits relative to the decimal point or total significant digits.

Decimal Places / Sig Figs Enter positive digits (e.g. 2 for hundredths) or negative digits (e.g. -2 for nearest hundred).

Rounding Rule The rule to apply for rounding boundary numbers.

Result

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Enter values and press Round.

How to round numbers

Rounding simplifies numbers, making them easier to read and work with, while keeping their value close to the original.

Identify the target place value: Find the digit at the position you are rounding to.
Look at the next digit to the right: If that digit is **5 or greater**, round up by adding 1 to your target digit and replacing all digits to its right with zeros. If that digit is **4 or less**, round down by keeping the target digit as-is and replacing all digits to its right with zeros.
Decimal Places (DP): Round relative to the decimal point. E.g. 12.345 to 2 DP is 12.35 (nearest hundredth), and to 0 DP is 12 (nearest integer). You can also use negative decimal places: rounding to -2 DP rounds to the nearest hundred (e.g. 152 rounds to 200).
Significant Figures (SF): Round to a specific count of important digits. Start counting at the first non-zero digit. E.g. 0.005432 to 2 SF is 0.0054.

Different rounding rules

Different applications require different rounding boundaries:

Standard (Half Up): Standard school rounding. Mid-point values (like 0.5) are rounded up. E.g., 2.5 → 3 and -2.5 → -2.
Ceiling (Up): Rounds towards positive infinity. Helpful when estimating maximum values. E.g., 2.1 → 3 and -2.9 → -2.
Floor (Down): Rounds towards negative infinity. Helpful for estimating minimum values. E.g., 2.9 → 2 and -2.1 → -3.

FAQ

What are significant figures?

Significant figures are digits that carry meaning contributing to its measurement resolution. Leading zeros are not significant (e.g., 0.05 has 1 SF). Embedded zeros (5.05 has 3 SF) and trailing zeros in a decimal number (5.50 has 3 SF) are significant.

How do you round to the nearest ten?

Select the "Decimal Places" mode and enter -1. For the nearest hundred, enter -2, and for the nearest thousand, enter -3.

Is banker's rounding supported?

This calculator uses standard Round-Half-Up as its default method. For custom scientific banker's rounding, please consult specialized statistics software.

Disclaimer. RapidRatio is informational only. It is not financial, tax, business, or professional advice. Verify results and assumptions with qualified professionals before making decisions.