Significant Figures in a Product Calculator

How it is calculated

The tool counts the significant figures of each operand as typed, keeps the smaller count n = min(sfA, sfB), multiplies or divides the two values, and rounds the raw answer to n significant figures. Counting rules in the code: leading zeros never count; with a decimal point every digit after the first non-zero digit counts, trailing zeros included (1.40 has 3, 0.00450 has 3); an integer written without a point counts all its digits after stripping leading zeros, so 1200 is treated as having 4 significant figures.

Write values in plain decimal form: scientific notation such as 1.2e3 shows no result, and neither does division by zero. A leading minus sign is ignored when counting. The rounded result is printed with only as many decimals as needed, so a result like 10 from 4 × 2.5 (1 significant figure) is shown as plain 10 and the sig-fig count beside it tells you how many of its digits are meaningful. Because digits are counted from the text, 4.0 and 4 behave differently.

Common mistakes

• Dropping a trailing zero when typing a measurement (writing 1.4 instead of 1.40); the digit count is read from the text, so the result keeps fewer figures than the instrument justified.
• Typing a round number like 1200 and expecting 2 significant figures; without a decimal point the tool counts all 4 digits, and the ambiguity is yours to resolve.
• Using the decimal-place rule from addition and subtraction; for products and quotients only the significant-figure count of the factors matters.
• Entering a value in scientific notation such as 1.2e3 and wondering why nothing appears; the tool needs plain decimal digits.
• Entering exact counted numbers or defined constants (such as 12 eggs) as measurements; these have unlimited significant figures and should not limit the result.