Rounding Calculator: Decimals, Significant Figures, Nearest 10
Enter a number, choose how to round it, and see the rounded value and how much it changed. Halves round away from zero.
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Formula
- Decimals:
round(x × 10^n) / 10^n - Significant figures:
n_dec = sig - 1 - floor(log10(|x|)), then round ton_decdecimals - Nearest 10 or 100:
round(x / 10) × 10,round(x / 100) × 100
Halves round away from zero.
Worked example
3.14159 to 2 decimals is 3.14; 123456 to 3 significant figures is 123000; 1234 to the nearest 100 is 1200.
Frequently asked questions
How do I round to 2 decimal places?
Look at the third decimal digit: 5 or more rounds up, otherwise down. 3.14159 has a 1 there, so it becomes 3.14.
What are significant figures?
Significant figures count digits from the first non-zero digit. 123456 to 3 significant figures is 123000, and 0.0012345 to 2 is 0.0012.
How does it round exact halves such as 2.5?
Away from zero: 2.5 becomes 3 and -2.5 becomes -3. Some systems round halves to the nearest even number instead, which gives 2.
How do I round to the nearest 10 or 100?
Divide by 10 (or 100), round to a whole number, then multiply back. 1234 to the nearest 10 is 1230, and to the nearest 100 is 1200. The "how many" box is ignored for these.