Pie Chart Calculator
Convert raw values into pie chart slices. Enter your category values separated by commas and get each slice as a percentage of the whole and as degrees of the circle — ready to draw with a protractor or to check against a finished chart.
Example: with Category values (comma separated) 40, 30, 20, 10 → Slice percentages: 40%, 30%, 20%, 10%.
- Slice angles (degrees)144°, 108°, 72°, 36°
- Total100 across 4 slices
- Largest sliceLargest: 40 — 40% of the pie (144°)
Computed by the calculator below using its default values. Change any input to see your own numbers.
Each slice’s angle = (value ÷ total) × 360°, because a full circle is 360°. The percentages and the degrees always describe the same share two ways.
From values to slices
A pie chart is just division made visible. Each category’s share of the total becomes its share of the circle: percentage = value ÷ total × 100, and angle = value ÷ total × 360. With values 40, 30, 20, 10 the total is 100, so the slices are 40%, 30%, 20%, 10% — or 144°, 108°, 72°, 36° for a protractor.
Two checks catch nearly every drawing error: the percentages must sum to 100 and the degrees to 360 (allow a tenth or two for rounding). If your degrees add to 350, a slice was computed from the wrong total — usually because one category was left out of the sum.
How it’s calculated
Percentage per slice = value ÷ total × 100. Angle per slice = value ÷ total × 360°. Values are parsed from a comma/space separated list; negatives and non-numbers are skipped and counted. Both outputs are rounded to one decimal place, so sums can drift from 100% or 360° by a rounding hair.
A pie chart only makes sense for parts of a single whole — categories must be non-overlapping and the values non-negative.
Worked example: values 40, 30, 20, 10
| Category | Value | Percent | Angle |
|---|---|---|---|
| A | 40 | 40% | 144° |
| B | 30 | 30% | 108° |
| C | 20 | 20% | 72° |
| D | 10 | 10% | 36° |
| Total | 100 | 100% | 360° |
Computed with value ÷ total × 100 and value ÷ total × 360.
Common mistakes
- Using 100 instead of 360 when computing angles — a 25% slice is 90°, not 25°.
- Computing shares from the wrong total by leaving a category out of the sum, so the degrees no longer add to 360.
- Feeding a pie chart categories that overlap or do not form a whole — use a bar chart for those.
- Rounding each slice down and wondering why the chart has a gap; keep one decimal and check the total.
Frequently asked questions
What is the pie chart formula?
Each slice’s angle = (value ÷ total) × 360°, and its percentage = (value ÷ total) × 100. A category worth 40 out of a 100 total gets 40% of the pie and a 144° slice.
Why do the degrees have to add up to 360?
Because the slices partition a full circle. If your computed angles sum to anything else beyond rounding, a value was missed or the wrong total was used.
Can I enter percentages directly?
Yes — percentages are just values that total 100. Enter 45, 30, 25 and the tool returns the same percentages and their angles (162°, 108°, 90°).
What if a value is zero?
A zero value is a 0% slice with a 0° angle — it simply does not appear in the drawn chart, though it stays in the list.