Significant Figures Rounder
Round any number to a chosen number of significant figures instantly — runs 100% in your browser with no upload.
Significant figures in your number: 6
3.14
Numeric value: 3.14
🔒 Rounded in your browser — nothing is uploaded.
What this tool does
Type a number and pick how many significant figures you want, and the result updates live. Significant figures are the digits in a number that carry real meaning about its precision, starting from the first non-zero digit. Rounding 3.14159 to 3 significant figures gives 3.14, and rounding 0.0045678 to 2 significant figures gives 0.0046 — the leading zeros in 0.0045678 are placeholders and do not count. The tool shows two forms of the answer: a formatted string that preserves trailing zeros so the precision is unambiguous (for example 2 rounded to 3 significant figures is shown as 2.00), and the plain numeric value (2) that you would use in further calculations. As you type, it also reports how many significant figures your number already has, reading the count from the number as written so 100 counts as 1, 100. as 3 and 1200.0 as 5.
How rounding to significant figures works
To round to n significant figures, you find the first non-zero digit and keep that digit plus the next n−1 digits, rounding the last kept digit based on what follows. The count ignores leading zeros but includes trailing zeros once they sit after a decimal point, which is why 2.00 and 2 mean different things about how precisely a value is known. This rounder uses the browser's built-in precision handling, so very large and very small numbers are rounded correctly and may be shown in scientific notation (for example 123456 to 3 significant figures becomes 1.23e+5, or 123000).
Frequently asked questions
What counts as a significant figure?
Every digit from the first non-zero digit onward is significant. Leading zeros (as in 0.0046) are only placeholders and are not counted, while trailing zeros after a decimal point (as in 2.00) are significant because they signal measured precision.
Why does the result show trailing zeros like 2.00?
Trailing zeros communicate precision. Rounding 2 to 3 significant figures gives 2.00 to show three meaningful digits. The tool also displays the plain numeric value (2) separately, so you can copy whichever form you need.
Is my number sent to a server?
No. The number you enter never leaves your device. All rounding runs entirely in your browser with JavaScript — nothing is uploaded, logged, or stored.