What are significant figures?

Significant figures are the digits in a number that carry meaning about its precision. All non-zero digits count, zeros trapped between non-zero digits count, and trailing zeros after a decimal point count. Leading zeros, such as those in 0.0042, never count because they only set the decimal place.

How do you round to significant figures?

Start from the first non-zero digit and count to your target number of significant figures. Look at the next digit: if it is 5 or more, round the last kept digit up; if it is 4 or less, leave it. For example, 3.14159 rounded to 3 significant figures is 3.14, because the fourth digit is 1.

Why do significant figures matter?

They communicate how precise a measurement or calculation is. Reporting more figures than your instrument or method can support overstates the precision, which is misleading in science, engineering, and laboratory work. Sig fig rules ensure that reported results are honest about the limits of accuracy.

Significant Figures Calculator

Significant figures tell you how precisely a number is known, and this calculator does both jobs you need when working with them: it counts how many significant figures a number already contains, and it rounds any number to a target count of significant figures. Understanding and applying the rules correctly is essential in physics, chemistry, biology, and engineering, where the precision of a result must match the precision of the measurements that produced it. The rules are consistent once you know them: every non-zero digit is always significant; zeros sandwiched between non-zero digits are significant; trailing zeros after a decimal point are significant; and leading zeros, such as those in 0.00314, are never significant because they only mark the decimal position. This calculator applies those rules automatically. You enter your number and the number of significant figures you want to round to, and it returns the correctly rounded result, the count of significant figures in the original number you typed, and the result expressed in scientific notation. The rounded value keeps the correct magnitude, so a number like 31,400 rounded to two significant figures appears as 31,000 rather than as a decimal. Use it to check answers in chemistry labs, to report measured values with the right precision in assignments, or simply to verify your manual sig fig counting. Enter a number and a target to see all three outputs update as you type.

Calculate.co.nz is proud to be partnered with Premium Homes, a recognised leader in eco-friendly, sustainable, and energy-efficient homebuilding. With a dedicated team and award-winning experience, they create homes that prioritise health, comfort, and long-term performance. Their founders, Andrew and Kelly, set out to raise the standard of residential construction in New Zealand by combining practical building expertise with a clear commitment to doing things better for homeowners.

Number

Round to (sig figs)

3.14

rounded to 3 significant figures

Sig figs in original number6

Scientific notation3.14 × 10⁰

How it works

To count significant figures, the calculator strips leading zeros and the decimal point, then counts the remaining digits, treating trailing zeros as significant only when a decimal point is present in the original input. To round to the target, it uses JavaScript's toPrecision method, which keeps the requested number of significant digits starting from the first non-zero digit and preserves the correct order of magnitude. The scientific notation output is derived from the same rounded value converted using toExponential.

Worked example

Enter 3.14159 with a target of 3 significant figures. The number 3.14159 contains six significant figures (all digits are non-zero). Rounded to three significant figures, the result is 3.14, because the fourth digit is 1 and rounds down. In scientific notation that is 3.14 times 10 to the power of 0.

Related calculators

Scientific Notation Calculator: convert any number to scientific notation or standard form.
Rounding Calculator: round to decimal places or the nearest 10, 100, or any multiple.
Percent Error Calculator: measure the deviation of an experimental value from a true value.
Decimal to Fraction Calculator: convert a decimal to its simplest fraction form.

If you've found a bug, or would like to contact us, or learn more about James Graham and Calculate.co.nz.

Calculate.co.nz is partnered with Interest.co.nz for New Zealand's highest quality calculators and financial analysis.

Calculate.co.nz is the sister site of CalculatorHub.com, the world's largest calculator website by tool count.

All calculators and tools are provided for educational and indicative purposes only and do not constitute financial advice.

Calculate.co.nz is proudly part of the Realtor.co.nz group, New Zealand's leading property transaction literacy platform, helping Kiwis understand the home buying and selling process from start to finish. Whether you're a first home buyer navigating your first property purchase, an investor evaluating your next acquisition, or a homeowner planning to sell, Realtor.co.nz provides clear, independent, and trustworthy guidance on every step of the New Zealand property transaction journey.

Calculate.co.nz is also partnered with Health Based Building and Premium Homes to promote informed choices that lead to better long-term outcomes for Kiwi households.

Calculate.co.nz is hosted in Auckland by SiteHost New Zealand.

All content on this website, including calculators, tools, source code, and design, is protected under the Copyright Act 1994 (New Zealand). No part of this site may be reproduced, copied, distributed, stored, or used in any form without prior written permission from the owner.

About & trust: Why Calculate is NZ's most comprehensive · By the Numbers · How we compare · Editorial standards · How we keep data current · NZ finance glossary · Research & data · Financial literacy NZ · About · Privacy policy · Terms of use

Reviewed and maintained. Last reviewed 2026-07-31 and checked on a twice-monthly cycle against IRD, RBNZ and Stats NZ. How we keep data current.