Significant Figures Calculator — Count, Calculate & Round Sig Figs Instantly
The go-to tool for students, scientists, and engineers. Perform arithmetic with automatic sig fig rounding, or simply count significant digits in any number.
What Are Significant Figures?
Significant figures (sig figs) are the meaningful digits in a number that convey the precision of a measurement. They tell you how many digits in a value are reliably known — which is critical in scientific and engineering calculations where accuracy matters.
When you measure 3.40 cm, the trailing zero is significant because it indicates precision to the hundredths place. But if you write 0.0045, those leading zeros are just placeholders — only the 4 and 5 are significant, giving the number 2 sig figs.
Sig fig rules govern how precision propagates through arithmetic operations. Multiplication and division follow a different rule than addition and subtraction — and getting them wrong can invalidate lab results, engineering calculations, and scientific reports.
Everything You Need, Built In
Sig Fig Counter
Enter any number — decimal, whole, or in scientific notation — and get the exact count of significant figures instantly.
Arithmetic with Auto-Rounding
Add, subtract, multiply, and divide numbers with automatic significant figure rounding applied to the result.
Scientific Notation Support
Enter values in E-notation (e.g., 3.5e3) and get results in both standard and scientific notation.
Step-by-Step Breakdown
See exactly how the result was determined — which sig fig rule was applied and why.
Exponentiation & Logarithms
Supports exponential and logarithmic operations with correct sig fig handling for each.
Least Significant Digit Highlight
The tool highlights the least significant digit in the result for quick visual verification.
Built for Everyone Who Needs It
Science Students
Chemistry, physics, and biology students who need to apply sig fig rules correctly in lab reports and homework.
Engineering Students
Engineers-in-training performing precision calculations where measurement accuracy is critical.
Lab Technicians & Researchers
Professionals verifying that experimental results maintain appropriate precision throughout calculations.
Teachers
Educators creating assignments, answer keys, and worked examples for science courses.
Sig Fig Rules — Quick Reference
| Non-zero digits | Always significant (e.g., 473 has 3 sig figs) |
| Zeros between non-zero digits | Always significant (e.g., 205 has 3 sig figs) |
| Leading zeros | Never significant (e.g., 0.0045 has 2 sig figs) |
| Trailing zeros after decimal | Always significant (e.g., 90.7500 has 6 sig figs) |
| Trailing zeros in whole number | Ambiguous without a decimal point (e.g., 1300 may have 2, 3, or 4) |
Sig Fig Rules for Arithmetic Operations
| Addition & Subtraction | Result has the same number of decimal places as the least precise measurement. |
| Multiplication & Division | Result has the same number of sig figs as the factor with the fewest. |
| Logarithms | The number of sig figs in the input becomes the number of decimal places in the result. |
| Exponentiation | Rounds based on the certainty in the base only. |
Frequently Asked Questions
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