Pie Chart Percentage Calculator

Enter a part value and the total to find what percentage of the whole it represents and the exact pie chart slice angle in degrees.

Quick Facts

Formula
Percentage = part / total x 100; slice angle = percentage x 3.6
A full pie is 360 degrees, so each 1% of the whole equals 3.6 degrees.

Your Results

Calculated
Percentage of whole
-
part / total x 100
Slice angle
-
degrees of the 360 circle
Fraction
-
part / total as a decimal

Ready

Enter a part value and the total, then press Calculate.

How to calculate a pie chart percentage

A pie chart divides a full circle among categories so each slice's size is proportional to its share of the total. To find any slice's percentage, divide that category's value (the "part") by the sum of all categories (the "total") and multiply by 100:

Percentage = (part / total) × 100

Because a whole circle is 360°, each slice's angle is proportional to the same fraction. You can get the angle either by multiplying the percentage by 3.6, or directly from the raw values:

Slice angle = (part / total) × 360 = percentage × 3.6

For example, if a category has a value of 40 out of a total of 200, its share is 40 / 200 = 0.20, which is 20% of the whole and a slice of 0.20 × 360 = 72°. Across every category the percentages must sum to 100% and the angles must sum to 360°.

Why the calculation is needed

Raw counts are hard to compare when totals differ. Converting each value to a percentage of the whole puts every category on a common 0–100 scale, which is what makes a pie chart readable. The angle conversion is the extra step you need if you are drawing the chart by hand or with a protractor, or verifying that a charting tool rendered slices at the correct size.

Common reference points

  • 1% of the whole = 3.6° of the circle.
  • 10% = 36°; 25% = 90° (a quarter, a right angle); 50% = 180° (a half); 75% = 270°.
  • A slice that fills the whole pie is 100% = 360°; an empty category is 0% = 0°.

Sanity checks

The percentage can never exceed 100% unless the part is larger than the total, which usually signals a data-entry mistake. If you total the percentages of every slice and do not land on 100% (allowing for tiny rounding), one of the parts or the total is wrong.

Frequently Asked Questions

How do you calculate a pie chart percentage?
Divide the part (one category's value) by the total of all categories, then multiply by 100. For example, 40 out of 200 is 40 / 200 × 100 = 20%. The percentages of every slice add up to 100%.
How do you convert a percentage into a slice angle?
A full circle is 360°, so each percent of the whole equals 3.6°. Multiply the percentage by 3.6, or compute the angle directly as part / total × 360. A 25% slice spans 90°; a 50% slice spans 180°.
Why don't my slice percentages add up to exactly 100%?
This is almost always rounding. If you round each slice to a whole percent, the displayed values can sum to 99% or 101%. Keep an extra decimal place, or adjust the largest slice so the total reads 100%.
Can a pie chart percentage be more than 100%?
No. Each part is a portion of the same total, so no single slice can exceed 100% and the slices together equal exactly 100%. If your result is above 100%, the part is larger than the total, which means the inputs are wrong for a pie chart.

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