Significant Figures Calculator

Enter any number including scientific notation (e.g., 1.23e5)

Try one 0.00450 1200 1.0023 1.23×10⁵
More examples
Leading zeros
0.00450 0.0123 0.500
Trailing zeros
1200 1200. 1200.0 120
Trapped zeros
1002 50.03 1.0023
Scientific notation
1.23×10⁵ 4.500×10⁻³ 6.02×10²³
Try one 12.34 + 5.6 1000 − 5.5 12.34 × 5.6 100 ÷ 3.0
More examples
Addition
12.34 + 5.6 100.5 + 23.456
Subtraction
45.67 − 12.3 1000 − 5.5
Multiplication
12.34 × 5.6 0.0045 × 123
Division
45.67 ÷ 12.3 100 ÷ 3.0
Try one 123.456 → 3 0.004567 → 2 12345 → 3 45.678 → 4
More examples
Basic
123.456 → 3 0.004567 → 2
Large numbers
12345 → 3 98765 → 2
Decimal numbers
45.678 → 4 0.123456 → 3
Try one 0.00456 123000 Avogadro's 1.23×10⁵
More examples
Small numbers
0.00456 0.0000789
Large numbers
123000 Avogadro's
Already scientific
1.23×10⁵ 4.5×10⁻³

Operators: + − × ÷  ·  Powers: ^ or **  ·  Functions: log ln sqrt exp sin cos tan arcsin/arccos/arctan abs  ·  Constants: pi e

Used by sin / cos / tan and inverse trig.
Try one log(102) log(102) + 2^10 √(2.0) π·5.5² 0.00450
More examples
Single number (counts sig figs)
0.00450 1200 1.23×10⁵
Arithmetic
(12.34 + 5.6) * 2.1 45.67 − 12.3 100.5 / 3.0 + 2.45
Logarithms
log(102) log(2.0) ln(10) exp(2.0)
Roots and powers
sqrt(2.0) sqrt(2) 2^10 2.0^3
Constants and mixed
π 2π πr² (r=5.5) log(102) + 2^10
Trig
sin(30) [deg] cos(45) [deg] tan(π/4) [rad]

Test your sig fig knowledge. Click an answer for each question.

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Sig Fig Calculator

Pick a mode above and enter a number to see the result with step-by-step explanation.

What Are Significant Figures?

Significant figures (sig figs) are the digits in a number that carry meaningful information about its precision. When you measure something with a ruler, balance, or instrument, every digit you record reflects how precise the measurement is. Mastering sig figs is essential in chemistry, physics, engineering, and any quantitative science.

Why it matters: Reporting too many digits implies false precision; too few discards real precision. Sig figs propagate measurement uncertainty correctly through calculations.

The 5 Rules for Counting Sig Figs

  1. All non-zero digits are significant.  e.g. 1234 has 4 sig figs.
  2. Trapped zeros are significant.  e.g. 1002 has 4 sig figs.
  3. Leading zeros are NOT significant.  e.g. 0.00450 has 3 sig figs (4, 5, 0).
  4. Trailing zeros after a decimal ARE significant.  e.g. 1.200 has 4 sig figs; 0.500 has 3.
  5. Trailing zeros without a decimal are AMBIGUOUS.  e.g. 1200 could have 2, 3, or 4 sig figs — use scientific notation to clarify (1.20 × 10³ = 3 sig figs).

Quick Reference

Number Sig figs Why
12344All non-zero
10024Trapped zeros count
0.004503Leading zeros don't count; trailing zero after decimal counts
1.2004Trailing zeros after decimal are significant
12002-4Ambiguous — rewrite as 1.2×10³ (2), 1.20×10³ (3), or 1.200×10³ (4)
6.02×10²³3Scientific form makes it unambiguous

Calculation Rules

Addition / Subtraction — round to the same number of decimal places as the value with the fewest.   e.g. 12.34 + 5.6 = 17.94 → 17.9 (1 dp).

Multiplication / Division — round to the same number of sig figs as the value with the fewest.   e.g. 12.34 × 5.6 = 69.104 → 69 (2 sf).

Frequently asked

Significant figures are the digits in a number that carry meaningful precision. Non-zero digits are always significant; trapped zeros are significant; leading zeros are not; trailing zeros after a decimal are significant; trailing zeros without a decimal are ambiguous.
Apply the 5 rules in order: (1) all non-zero digits, (2) trapped zeros count, (3) leading zeros don't, (4) trailing zeros after a decimal do, (5) trailing zeros without a decimal are ambiguous — use scientific notation to clarify.
Round the result to the same number of decimal places as the operand with the fewest decimal places. Example: 12.34 + 5.6 = 17.94 → 17.9 (one decimal place, matching 5.6).
Round the result to the same number of sig figs as the operand with the fewest sig figs. Example: 12.34 × 5.6 = 69.104 → 69 (two sig figs, matching 5.6).
Trailing zeros after a decimal are always significant (1.200 has 4 sig figs). Trailing zeros in a whole number without a decimal are ambiguous — rewrite in scientific notation: 1.20 × 10³ = 3 sig figs.
Identify the nth significant digit, then look at the next digit. If it's 5 or greater, round up. Example: 123.456 to 3 sig figs → 123 (the next digit, 4, rounds down).