Sig Figs Calculator
Count significant figures, round to any sig fig count, or solve expressions — with step-by-step explanations.
Based on standard significant figure rules used in chemistry, physics, and measurementSignificant Figures Calculator
Try these examples:
How to use this calculator
- Choose a mode. Select Count, Round, Calculate, or Scientific Notation from the tabs.
- Enter your number or expression. Type any number, decimal, negative number, or an expression like 4.56 × 2.1.
- Read the result. You will see the answer, the rule applied, and a step-by-step explanation.
Not sure which mode to use? Start with Count — it works for most questions.
Significant figures rules — quick reference
The 6 core rules, each with an example.
Non-zero digits
4.56 → 3 sig figs
All non-zero digits (1–9) are always significant.
Captive zeros
1.002 → 4 sig figs
Zeros between two non-zero digits are always significant.
Leading zeros
0.0034 → 2 sig figs
Zeros before the first non-zero digit are never significant.
Trailing zeros (with decimal)
1.200 → 4 sig figs
Trailing zeros after a decimal point are always significant.
Trailing zeros (no decimal)
1000 → ambiguous
Trailing zeros in whole numbers are ambiguous without a decimal point.
Exact numbers
12 eggs → unlimited
Counted or defined values have unlimited significant figures.
Worked examples
Click any example to load it in the calculator.
Leading zeros are placeholders. The 3, 4, and trailing 0 after the decimal are significant.
All trailing zeros after a decimal point are always significant.
Trailing zeros in a whole number are ambiguous. Write 1000. or 1.000 × 10³ to be precise.
Multiplication — answer limited to 2.1's 2 sig figs.
Addition — answer limited to 0.3's 1 decimal place.
Only the 5 is significant. All leading zeros are placeholders.
Common mistakes with significant figures
✗ Confusing sig figs with decimal places
Decimal places count digits after the decimal point. Significant figures count all meaningful digits. 0.00340 has 5 decimal places but only 3 significant figures.
✗ Assuming trailing zeros in whole numbers are always significant
500 looks like 3 sig figs, but the zeros may just be placeholders. Write 5.00 × 10² to clearly show 3 sig figs.
✗ Applying the wrong operation rule
Addition and subtraction use the fewest decimal places rule. Multiplication and division use the fewest sig figs rule. They are not the same.
✗ Treating exact numbers like measured values
Exact counts (12 items, 100 cm in a meter) have unlimited sig figs and should never limit your answer.
Frequently asked questions
Quick answers to the most common significant figures questions.
Learn more about significant figures
Explore rules, examples, and operation guides.
Significant Figures Rules
Every rule explained with clear examples.
Rounding to Sig Figs
Step-by-step rounding guide with worked examples.
Addition & Subtraction
The decimal place rule explained simply.
Multiplication & Division
The fewest sig figs rule with examples.
Scientific Notation
How sig figs work in scientific notation.
Examples Hub
Browse all worked significant figures examples.