Rounding Calculator
Round numbers to any decimal place or significant figure with multiple rounding methods.
A rounding calculator rounds numbers to a specified place value or significant figures, showing floor and ceiling values alongside the result.
Examples
Decimal places
Whole numbers
Significant figures
Frequently Asked Questions
What are significant figures?
What happens when the digit is exactly 5?
Why does rounding matter?
Quick Tips
- •Double-check your inputs — small errors lead to incorrect results.
- •Use significant figures mode when working with scientific measurements.
- •Be aware that some scientific contexts use bankers rounding (round half to even) instead of standard rounding.
A rounding calculator rounds numbers to a specified place value or significant figures, showing floor and ceiling values alongside the result.
How to Use This Calculator
Enter a number and select where to round (place value or significant figures). The calculator shows the rounded result along with floor and ceiling values.
Understanding the Formula
Standard rounding: if the digit to the right of the rounding position is 5 or greater, round up; otherwise, round down. Significant figures count all meaningful digits from the first non-zero digit.
Examples
Decimal places
3.14159 rounded to hundredths = 3.14 (9 < 5 at thousandths would give 3.142, but hundredths looks at 1)
Whole numbers
3,456 rounded to hundreds = 3,500 (56 rounds up)
Significant figures
0.004567 to 2 sig figs = 0.0046 (first two non-zero digits: 4 and 5, then round)
Frequently Asked Questions
What are significant figures?
Significant figures are all digits that carry meaning, starting from the first non-zero digit. Leading zeros are not significant. For example, 0.00450 has 3 significant figures.
What happens when the digit is exactly 5?
Standard convention rounds up when the digit is 5. Some scientific contexts use "round half to even" (banker's rounding) to reduce bias.
Why does rounding matter?
Rounding communicates precision. Reporting a measurement as 3.14 vs 3.14159 indicates different levels of certainty about the value.
Assumptions & Limitations
- Assumes standard rounding rules where 5 rounds up.
- Assumes exact input values; rounding in inputs propagates to results.
- Results may show floating-point approximations for irrational numbers.