Significant figures

Trailing zeros can carry meaning

A displayed trailing zero can indicate retained precision. Scientific notation is useful when the significant digits of a large or very small number would otherwise be ambiguous. Check the formatted answer rather than counting only digits after the decimal point.

Round at the end of a calculation

Repeated rounding of intermediate values can change a final answer. Keep working precision until the reporting step. This tool rounds the number you provide; it does not infer measurement uncertainty or propagate significant figures through a complete calculation.

Choosing significant figures or decimal places

The number 12.345 rounded to three significant figures is 12.3, while rounding it to three decimal places leaves 12.345. The two instructions answer different reporting needs. Significant figures keep a chosen number of meaningful digits across different magnitudes. Decimal places set the position of the last retained digit relative to the decimal point.

When a rounded value ends in zeros, scientific notation can make the intended precision clearer. For example, writing a value as 1.20 × 10³ explicitly retains three significant figures; an isolated 1200 can be ambiguous without context. Do not choose precision solely from the number of digits a calculator displays. Measurement resolution, calibration uncertainty, and the purpose of the reported result can all matter. Keep a full-precision working value for later arithmetic and a separately rounded value for presentation. This avoids accumulating rounding changes while preserving a readable final answer. The tool performs numeric rounding, not an assessment of which precision your measurement method supports.

Formula

Round to n significant figures; retain trailing zeros that indicate precision.