Significant Figures Calculator

About Significant Figures Calculator

Significant figures indicate the precision of a measurement. Leading zeros are not significant; trailing zeros after a decimal point are.

How to use this calculator

1. Enter the number you want to round, such as 482.76 or 0.004391.
2. Choose how many significant figures you want, like 2, 3, or 4.
3. Check the rounded result and compare it with the original value.
4. Use the result in calculations or reports where a specific level of precision is required.

The formula explained

The formula $$sig\_figs(x, n)$$ computes the value of \(x\) rounded to \(n\) significant figures. It keeps the leading meaningful digits and rounds based on the next digit.

• x = the original number you want to round
• n = the number of significant figures to keep

Step by step method

1. Find the first nonzero digit in the number, then count that digit as the start of the significant figures.
2. Keep the first \(n\) significant digits, and look at the next digit to decide whether to round up or stay the same.
3. If the number is less than 1, use the first nonzero digit after the decimal point as the start of the count.

Worked example

Problem. Round 0.004391 to 3 significant figures.

1. The first nonzero digits are 4, 3, and 9, so the first 3 significant figures are 4.39.
2. Look at the next digit, which is 1, so the third digit does not round up.
3. The rounded value is 0.00439.

Tips and common mistakes

• Leading zeros do not count as significant figures, so 0.004391 has 4 significant figures, not 7.
• If a number ends in zeros, write it carefully, because 1200 may have 2, 3, or 4 significant figures depending on how it is written.

Frequently asked questions