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Rounding Calculator – Round to Decimal Places or Sig Figs

Round any number to a specified number of decimal places or significant figures with our free online rounding calculator. Supports standard and scientific rounding rules.

Rounding Calculator
Round numbers to decimal places, significant figures, or integers.
Examples:

Rounding Calculator – Round to Decimal Places or Sig Figs

Rounding simplifies numbers while keeping them close to their original value. Whether you need 2 decimal places for currency, 3 significant figures for a lab report, or just the nearest whole number, this calculator handles it with multiple rounding methods.

Different situations call for different rounding rules. School math typically uses "round half up" – 2.5 becomes 3. But scientists and statisticians often prefer "round half even" (banker's rounding) to avoid systematic bias. This calculator lets you choose the method that fits your needs.

Rounding Methods Explained

Round Half Up (Standard)

The most common method. If the digit after your rounding position is 5 or greater, round up. Otherwise, round down.

2.5 → 3
2.4 → 2
3.14159 to 2 decimals → 3.14
3.145 to 2 decimals → 3.15

Round Half Even (Banker's Rounding)

When the digit is exactly 5, round to the nearest even number. This reduces bias in large datasets. Used in IEEE 754 floating-point standard.

2.5 → 2 (round to even)
3.5 → 4 (round to even)
2.45 to 1 decimal → 2.4
2.55 to 1 decimal → 2.6

Round Half Down

Opposite of half-up. When the digit is exactly 5, round down instead of up.

2.5 → 2
2.6 → 3
3.145 to 2 decimals → 3.14

Ceiling (Round Up)

Always round toward positive infinity. Any fractional part causes rounding up.

2.1 → 3
2.9 → 3
-2.1 → -2

Floor (Round Down)

Always round toward negative infinity. Any fractional part causes rounding down.

2.1 → 2
2.9 → 2
-2.1 → -3

Significant Figures

Significant figures (sig figs) count all digits that carry meaning about a measurement's precision. Leading zeros don't count. Trailing zeros after a decimal do count.

0.001233 sig figs
123.455 sig figs
100.04 sig figs
1001 sig fig (ambiguous)
0.00011 sig fig
1.00 × 10²3 sig figs

Rounding Examples

Currency (2 decimal places)
$12.3456 → $12.35 | $12.344 → $12.34
Scientific measurement (3 sig figs)
0.0012345 → 0.00123 | 12345 → 12300
Temperature (1 decimal place)
98.67°F → 98.7°F | 98.64°F → 98.6°F
Population (nearest thousand)
1,234,567 → 1,235,000 | 1,234,200 → 1,234,000
Pi approximation
3.14159265... → 3.14 (2 dp) | 3.142 (3 dp) | 3.1416 (4 dp)

Frequently Asked Questions

Why use banker's rounding?

Standard rounding (half up) introduces a slight upward bias because 5 always rounds up. Banker's rounding (half even) rounds 5 to the nearest even number, balancing out over many calculations. It's the default in Python, IEEE 754, and many statistical applications.

How many decimal places for money?

Most currencies use 2 decimal places (cents, pence, euro cents). Some, like the Japanese Yen, use 0. Cryptocurrencies often use 8 (Bitcoin) or 18 (Ethereum) decimal places.

What's the difference between decimal places and significant figures?

Decimal places count digits after the decimal point. Significant figures count all meaningful digits from the first non-zero digit. 0.00123 has 5 decimal places but only 3 significant figures.

When should I round in calculations?

Keep full precision during intermediate steps. Round only the final answer. Early rounding introduces cumulative errors that can significantly affect results.

Can I round negative numbers?

Yes. The same rules apply. For half-up: -2.5 rounds to -3 (away from zero). For half-even: -2.5 rounds to -2 (to even). Ceiling and floor work with the number line direction.

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