🔢

Significant Figures Calculator

Round numbers to the correct significant figures

Number

Significant Figures

📚 Examples, Rules & Help

Counting Rules

Non-zero digits are always significant

Zeros between non-zero digits are significant

Leading zeros are not significant

Trailing zeros in decimals are significant

Rounding Rules

If the digit after your target is ≥ 5, round up.

If it's < 5, round down.

12300 → 3 sig figs (ambiguous - use 1.23 × 10⁴ to clarify)

0.00456 → 3 sig figs (leading zeros don't count)

105.0 → 4 sig figs (decimal point makes trailing zero significant)

2.50 → 3 sig figs (trailing zero after decimal counts)

1.000 → 4 sig figs (all zeros after decimal are significant)

506 → 3 sig figs (zero between non-zeros counts)

3.40 × 10⁵ → 3 sig figs (scientific notation clarifies)

0.0090 → 2 sig figs (leading zeros don't count, trailing zero does)

Quick Decimal Check

For decimals like 0.00456, cover the leading zeros with your finger. The remaining digits (456) are your significant figures.

The Decimal Point Trick

If there's a decimal point, trailing zeros count: 1200.0 has 5 sig figs, but 1200 is ambiguous (2-4 sig figs).

Scientific Notation Shortcut

When unsure about trailing zeros, convert to scientific notation first: 1200 → 1.2 × 10³ (clearly shows 2 sig figs).

Rounding Strategy

Find your target digit, look at the next digit. If it's 5 or higher, round up. If it's 4 or lower, round down.

Common Mistake to Avoid

Don't count leading zeros! In 0.0045, only the 4 and 5 are significant. The zeros just show position.

Lab Report Tip

Match your answer's precision to your least precise measurement. If you measure 12.3 cm and 4.567 cm, your result should have 3 sig figs max.

What is Scientific Notation?

A way to write very large or very small numbers using powers of 10

How to Read It

• 1.23e+5 means 1.23 × 10⁵ = 123,000

• 4.56e-3 means 4.56 × 10⁻³ = 0.00456

• E-notation is the same as scientific notation, just with 'e' instead of '×10'

When to Use It

Scientific notation is preferred for very large numbers (≥1,000,000) or very small numbers (≤0.0001) to avoid ambiguity about significant figures.