Significant Figures Calculator

Count significant figures and round numbers to the correct precision. Supports scientific notation and e notation.

Count significant figures and round to specific sig figs. Supports decimals, scientific notation (3.5e3), and whole numbers.

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Counting Significant Figures

Enter whole numbers, real numbers, scientific notation or e notation to count significant figures. Example inputs: 3500, 35.0056, 3.5 x 10^3, or 3.5e3. The calculator identifies which digits are significant and explains why.

Significant Figures Rules:

Non-zero digits are always significant
Zeros between non-zero digits are always significant
Leading zeros are never significant
Trailing zeros are only significant if the number contains a decimal point

Rules for Adding/Subtracting:

Round the answer to the place position of the least significant digit in your least certain number. Focus on decimal place position, not total sig figs.

Rules for Multiplying/Dividing:

Round the answer to the fewest number of significant figures found in any of the original numbers in your calculation.

infoWhat is Significant Figures Calculator?expand_more

Significant figures (also called significant digits or sig figs) are the digits in a number that carry meaningful information about its precision. They indicate how accurate a measurement or calculation is, which is essential in scientific and engineering work.

When performing calculations, your result should not be more precise than your least precise measurement. For example, if you multiply 2.5 (2 sig figs) by 3.42 (3 sig figs), your answer should be rounded to 2 significant figures because 2.5 is the least precise number.

Important note: When using constants or exact values in formulas (like the 2 in d = 2r for circle diameter), treat them as having infinitely many significant figures, or at least as many as your least precise measurement.

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Identifying Significant Figures:

• 81 → 2 sig figs (8, 1)

• 0.007 → 1 sig fig (7 only, leading zeros don't count)

• 5200.38 → 6 sig figs (5, 2, 0, 0, 3, 8)

• 380.0 → 4 sig figs (trailing zero after decimal counts)

• 78800 → 3 sig figs (ambiguous trailing zeros)

Addition/Subtraction Rule:

Round to the least precise decimal position

Example: 7 + 2 + 0.063 = 9.063 → rounds to 9

(7 and 2 are only precise to the ones place)

Multiplication/Division Rule:

Round to the fewest significant figures

Example: 343 × 4.3148688 / 52 = 28.4615...

→ rounds to 28 (52 has only 2 sig figs)

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Example 1: Counting Sig Figs

26.2 → 3 sig figs (2, 6, 2 - all non-zero)

0.007 → 1 sig fig (only 7 - leading zeros don't count)

5200.38 → 6 sig figs (all digits including embedded zeros)

78800. → 5 sig figs (decimal point makes trailing zeros significant)

Example 2: Addition with Sig Figs

Adding fluids: 7 oz + 2 oz + 0.063 oz

Raw calculation: 9.063 oz

7 and 2 are precise only to the ones place

Rounded answer: 9 oz

Example 3: Multiplication with Sig Figs

Wavelength = (343 × 4.3148688) / 52

Raw calculation: 28.4615384 meters

52 has the fewest sig figs (2)

Rounded answer: 28 meters

Example 4: Constants in Formulas

Circle diameter: d = 2r, with r = 2.35

The constant 2 should be treated as 2.00 (3 sig figs)

Calculation: 2.00 × 2.35 = 4.70

Answer: 4.70 (not 5)

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Why are significant figures important in science?expand_more

Significant figures communicate the precision of a measurement. In scientific work, your calculated result shouldn't imply more precision than your original measurements. This prevents misleading conclusions and ensures data integrity.

Are trailing zeros without a decimal point significant?expand_more

This is ambiguous. The number 78800 could have 3, 4, or 5 significant figures. To clarify intent, use scientific notation (7.88 × 10⁴ for 3 sig figs, 7.8800 × 10⁴ for 5 sig figs) or add a decimal point (78800. indicates 5 sig figs).

How do I handle exact numbers and constants?expand_more

Exact numbers (like counting 12 eggs or the 2 in d=2r) have infinite significant figures and don't limit your answer. When entering constants in calculations, give them at least as many sig figs as your least precise measurement.

What's the difference between sig figs rules for addition vs multiplication?expand_more

Addition/subtraction: round to the least precise decimal place position. Multiplication/division: round to the fewest number of significant figures. These different rules account for how errors propagate in each operation type.

How do I round to significant figures?expand_more

Identify the last significant digit to keep, look at the next digit. If it's 5 or greater, round up; if less than 5, round down. For example, 28.4615 rounded to 2 sig figs: the second sig fig is 8, the next digit is 4, so round down to 28.