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Significant figures calculator

Round a number to a chosen number of significant figures.

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Need Rounded value? The Significant figures calculator derives it from Number, Significant figures in one step. For instance, with Number = 3.142 and Significant figures = 3 it returns Rounded value = 3.14.

How to use it

  1. Enter your values: Number, Significant figures.
  2. Read the result instantly: Rounded value.

Frequently asked questions

How does the Significant figures calculator work?

It takes Number and Significant figures and derives Rounded value from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

2 values: Number and Significant figures. Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Number = 3.142 and Significant figures = 3, the calculator returns Rounded value = 3.14. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

When would I actually use this?

Reading a number written another way: a Roman numeral on a monument, a hexadecimal colour, a binary byte, or a fraction that needs reducing.

What is the most common mistake?

Assuming a decimal fraction survives a change of base. A tenth is exact in decimal and infinitely repeating in binary, which is why 0.1 + 0.2 is not 0.3 in most programming languages.

What is the difference between the Significant figures calculator and the Rounding calculator?

Both return Rounded value. What differs is what they ask for: this one wants Significant figures, the Rounding calculator wants Decimal places. Use whichever matches the numbers you already have.

Is there a tool for the next step?

Ceiling and floor function calculator is the closest one after this: The ceiling ⌈x⌉ rounds up to the next integer, the floor ⌊x⌋ rounds down. Enter any number to get both, plus the ordinary round, the truncation toward zero and the fractional part left over.

What else is worth having open alongside it?

Amicable Number Checker and Arctan2 Calculator (atan2 of y and x) — they come up in the same task often enough to be worth a second tab.

Where do the figures come from, and how current are they?

Base conversion and number-theory results are exact. Roman numerals follow the standard subtractive form used since the Middle Ages, which is not the only one the Romans themselves used.

Further reading

All guides →
ExplainerSignificant Figures Explained: Counting, Rounding, and Why They MatterLearn what counts as a significant figure, the rules for leading, trailing, and captive zeros, and how sig figs keep your calculated answers honest.How-toHow to Round Numbers: Round Half Up, Round Half to Even, and MoreRound to any decimal place or number of significant figures, and learn when to use round half up versus round half to even to avoid bias.How-toHow to Find Prime Factors: Factor Trees and the Division MethodBreak any whole number into its prime building blocks with a factor tree or repeated division — and write the result as a clean prime factorization with exponents.How-toHow to Use the Quadratic Formula: Solving ax² + bx + c = 0Solve any quadratic equation with x = (−b ± √(b² − 4ac)) / 2a, and read the discriminant to know how many real solutions to expect.How-toHow to Do Long Division: Divide, Multiply, Subtract, Bring DownLong division breaks a big division into a repeating four-step cycle. Learn the divide-multiply-subtract-bring-down loop and how to read the remainder, with a worked example.ExplainerOrder of Operations (PEMDAS / BODMAS): Why the Order MattersPEMDAS and BODMAS are two names for one rule that fixes the order you evaluate a math expression — so everyone gets the same answer. Learn the rule with a worked example.