Significant Figures in Scientific Notation

Q: How do you count significant figures in scientific notation?

Count only the digits in the coefficient (the number before × 10ⁿ). The exponent does not contribute any significant figures. In 3.40 × 10⁻³, the coefficient is 3.40, which has 3 sig figs.

Q: Does the exponent count as a significant figure?

No. The exponent in scientific notation only sets the scale of the number. It carries no information about measurement precision. Only the coefficient determines sig fig count.

Q: Why is 1.000 × 10³ clearer than 1000?

1000 is ambiguous — it could have 1 to 4 sig figs. 1.000 × 10³ clearly shows 4 sig figs because the coefficient has 4 digits. Scientific notation removes all trailing zero ambiguity.

Q: How do you add two numbers in scientific notation with sig figs?

Align the exponents first, then add the coefficients. Apply the addition rule: the answer is limited to the fewest decimal places in the coefficients after alignment. For example, 1.23 × 10² + 4.5 × 10¹ = 123 + 45 = 168, but 1.23 × 10² has 2 decimal places as a plain number and 45 has 0, so the answer rounds to 170, or 1.7 × 10².

Scientific notation removes trailing zero ambiguity. Only the coefficient counts for sig figs — the exponent never does.

Try the Scientific Notation tab →See Rule 7

Reviewed by the Sig Figs Calc Editorial Team · Last updated April 2025 · See methodology

What is scientific notation?

Scientific notation expresses any number as a coefficient multiplied by a power of 10: A × 10ⁿ, where A is between 1 and 10.

For example, 0.00340 becomes 3.40 × 10⁻³. The number 6500 becomes 6.5 × 10³ (if 2 sig figs are intended) or 6.500 × 10³ (if 4 sig figs are intended).

The key rule

In scientific notation, only the coefficient (A) determines the number of significant figures. The exponent (n) sets the scale but carries no sig fig information.

How to count sig figs in scientific notation

Count the digits in the coefficient. Apply all standard sig fig rules to the coefficient only.

3.40 × 10⁻³coefficient: 3.403 sfTrailing zero after decimal is significant — 3 sig figs.

1.0 × 10⁴coefficient: 1.02 sfThe decimal zero is significant — 2 sig figs.

5.670 × 10⁸coefficient: 5.6704 sfTrailing zero after decimal — 4 sig figs.

2 × 10⁶coefficient: 21 sfOnly one digit in coefficient — 1 sig fig.

6.022 × 10²³coefficient: 6.0224 sfAvogadro's number — 4 sig figs shown.

How scientific notation removes trailing zero ambiguity

Numbers like 1000, 500, and 100 are ambiguous in plain form — you cannot tell how many trailing zeros are significant. Scientific notation solves this by putting all significant digits in the coefficient.

1000ambiguous

1 sig fig:1 × 10³

2 sig figs:1.0 × 10³

3 sig figs:1.00 × 10³

4 sig figs:1.000 × 10³

→ See full worked example: How many sig figs in 1000? →

500ambiguous

1 sig fig:5 × 10²

2 sig figs:5.0 × 10²

3 sig figs:5.00 × 10²

→ See full worked example: How many sig figs in 500? →

100ambiguous

1 sig fig:1 × 10²

2 sig figs:1.0 × 10²

3 sig figs:1.00 × 10²

→ See full worked example: How many sig figs in 100? →

Sig figs in operations with scientific notation

Multiplication and division

Multiply the coefficients. Add the exponents. Apply the fewest-sig-figs rule to the coefficients.

3.0 × 10² × 2.10 × 10³

Coefficients: 3.0 (2 sf) × 2.10 (3 sf) → limit to 2 sf

3.0 × 2.10 = 6.30 → rounded to 2 sf = 6.3

Answer: 6.3 × 10⁵

See full multiplication guide →

Addition and subtraction

Convert to the same exponent first. Then add the coefficients. Apply the fewest-decimal-places rule.

1.23 × 10² + 4.5 × 10¹

Convert: 123 + 45 = 168

Limit: 4.5 × 10¹ = 45, which has 0 decimal places at the 10² scale → round to tens

Answer: 1.7 × 10²

See full addition guide →

Frequently asked questions

How do you count significant figures in scientific notation?

Does the exponent count as a significant figure?

Why is 1.000 × 10³ clearer than 1000?

How do you add two numbers in scientific notation with sig figs?

Explore rules, examples, and operation guides.

Sig Figs Calculator

Convert any number to scientific notation with sig figs shown.

Significant Figures Rules

See Rule 7 — sig figs in scientific notation.

Rounding to Sig Figs

Rounding the coefficient to the correct sig fig count.

Multiplication & Division

How the fewest sig figs rule applies in scientific notation.

Sig Figs in 1000

Why 1000 is ambiguous and how notation fixes it.

Examples Hub

Scientific notation examples and more.