Pie Chart Calculator

Enter your category values and get each slice's percentage and degree angle, with the total and step-by-step working.

Quick Facts

Method
Share = value ÷ total; angle = share × 360°
Percentages sum to 100% and angles sum to 360°.

Your Results

Calculated
Total of all values
-
Sum of every category
Number of slices
-
Categories with a positive value

Ready

Enter your category values and press Calculate.

How the Pie Chart Calculator works

A pie chart splits a full circle into wedges, one per category, where each wedge's size is proportional to that category's share of the whole. This calculator takes the raw value of each category, adds them into a total, and then converts every value into two things: the percentage of the total it represents, and the angle in degrees that its slice occupies.

The two formulas are simple and exact:

  • Percentage of a slice = (category value ÷ total of all values) × 100
  • Angle of a slice = (category value ÷ total of all values) × 360°

Because a full circle is 360°, every category's share of the circle equals its share of the total. If a category is 25% of the data, its slice is 25% of the circle, which is 0.25 × 360 = 90°. The percentages of all slices always sum to 100%, and the angles always sum to 360°.

A worked example

Suppose a household budget is Rent 30, Food 20, and Transport 10. The total is 30 + 20 + 10 = 60. Rent's share is 30 ÷ 60 = 0.5, so its slice is 50% and 0.5 × 360 = 180°. Food is 20 ÷ 60 = 0.333, giving 33.33% and 120°. Transport is 10 ÷ 60 = 0.167, giving 16.67% and 60°. The percentages add to 100% (50 + 33.33 + 16.67) and the angles add to 360° (180 + 120 + 60).

Why the angle matters

If you are drawing a pie chart by hand or in a design tool, the angle is what you actually measure with a protractor to mark each wedge. Spreadsheet and charting software does this conversion automatically, but knowing the formula lets you verify a chart, reproduce one manually, or check that a graphic is drawn to scale rather than eyeballed.

Common reference points

  • Half the total → 50% → 180° (a semicircle).
  • A quarter of the total → 25% → 90° (a right angle).
  • A third of the total → 33.33% → 120°.
  • A tenth of the total → 10% → 36°. In fact, every 1% of the total equals exactly 3.6°.

Frequently Asked Questions

How do you calculate the angle of a pie slice?
Divide the category's value by the total of all values to get its share, then multiply by 360°. A category worth 25 out of a total of 100 has a share of 0.25 and an angle of 0.25 × 360 = 90°. Every 1% of the total equals 3.6°.
How do you turn values into percentages for a pie chart?
Each category's percentage is its value divided by the total of all values, times 100. For example, 20 out of a total of 60 is 20 ÷ 60 × 100 = 33.33%. All the slice percentages add up to 100%.
What if my values are percentages that don't add to 100?
That is fine — the calculator normalizes for you. It sums whatever values you enter and divides each by that total, so entering 45, 30, and 15 (which sum to 90) still produces slices that fill the whole circle in the correct proportions.
Can a pie chart show negative values?
No. A pie represents parts of a single whole, and a slice cannot occupy negative area, so this calculator rejects negative inputs. If your data contains negatives (for example, profit and loss), a bar chart is the appropriate tool instead.

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