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Significant Figures Calculator

Count significant figures in a written number and round to your chosen precision.

Your numbers

Make it your own
Updates as you type
Rounded to 3 significant figures
0.00450

Calculated from your inputs · rounded for display

Input significant figures4
Numeric value0.0045

For clarity, use scientific notation when trailing zeros are significant. Input is preserved as text for counting; rounding uses IEEE-754 arithmetic and may show binary floating-point tie behavior.

Your calculation, step by step

No black boxes
  1. Read the written mantissa 0.004500; leading zeros do not count.
  2. Trailing zeros count when a decimal point is written. Without a decimal point, terminal zeros are treated as placeholders.
  3. Round to 3 significant figures: 0.00450.

How to use this calculator

  1. Enter your own values in the labeled fields. Check the units and assumptions before comparing results. Only the fields needed for your selected calculation mode are shown.
  2. Your answer updates automatically. Review the calculation steps to see exactly how it was calculated.
  3. Copy, share, save, or download your result. Saved inputs stay on this device.

How the calculation works

Ignore leading zeros; keep decimal trailing zeros; round to the chosen significant-digit count

The written form carries precision information that a numeric value alone cannot preserve. Leading zeros locate the decimal point. Trailing zeros count when a decimal point is written; integer trailing zeros without a decimal point are treated as placeholders. Use scientific notation to make ambiguous precision explicit.

A worked example

0.004500 has four significant figures. Rounded to three significant figures, it is 0.00450.

Reading your result

Use the main result together with its units and supporting figures. Display values are rounded; calculations keep their underlying precision. A change in inputs or assumptions can change the answer. Compare the step-by-step working with your intended use before relying on an estimate.

Frequently asked questions

How is 1200 interpreted?

As two significant figures. Write 1.200e3 or 1200. to indicate four.

Does this infer measurement uncertainty?

No. It interprets written digits under the stated convention.

Sources & methodology

This calculator uses the mathematical identity and assumptions stated above. No current rates, prices, or external data are loaded. Conversion tools use international unit definitions.

Formula review: October 24, 2026. Read our methodology.