Slice share
slice % = slice value / total value x 100
Chart generator
Pie Chart Generator
Create clear proportion charts from slice labels and numeric values, with automatic percentages and PNG export.
Calculator
Enter pie slices
Add a label and numeric value for each slice. The generator turns the values into proportional pie segments and shows labels, values, and percentages on hover.
Result
About this tool
How it works
The EngLab Pie Chart Generator is a free online chart maker for visualizing part-to-whole relationships. It converts labelled values into an interactive pie chart so proportions, percentages, allocations, survey responses, cost breakdowns, material shares, and project summaries are easier to communicate. Use it when you need a quick pie chart for reports, presentations, dashboards, engineering documentation, budget summaries, or classroom examples without opening spreadsheet software.
Use cases
When to use a pie chart
A pie chart is useful when the main question is how a total is divided into parts. Common examples include project cost breakdowns, manufacturing defect categories, material composition, time allocation, survey response shares, budget distribution, market share, energy use by subsystem, and resource allocation. The chart is most effective when the categories are familiar, the number of slices is limited, and the largest differences are visually obvious.
Best practice
How to make the chart easier to read
Use concise labels, combine very small categories into an Other slice when appropriate, and keep all values in the same unit. A pie chart should explain proportion at a glance; if the audience needs to compare many small differences, create a bar chart instead. For engineering reports, include the source values near the chart so reviewers can verify the percentages.
Data entry
What values can be entered
The generator accepts positive numeric values such as counts, costs, weights, hours, votes, percentages, quantities, or measured totals. The values do not need to add to 100 because the tool calculates each slice percentage from the total automatically. For percentage-based inputs, make sure the values all refer to the same total before using the chart.
Formulas
Chart form used
Total value
total value = sum of all slice values
Angle of a slice
slice angle = slice value / total value x 360 degrees
Worked example
Example inputs
Example: enter Materials = 45, Labour = 30, Equipment = 15, and Other = 10. The total is 100, so the chart shows Materials as 45%, Labour as 30%, Equipment as 15%, and Other as 10%. If the same categories were entered as 450, 300, 150, and 100, the pie chart would show the same percentages because pie charts compare relative share rather than absolute scale.
Guide
How to use this calculator
- Add one slice row for each category you want to compare.
- Enter a short slice label, such as Materials, Testing, Manufacturing, Labour, Software, or Other.
- Enter a positive numeric value for each slice. Values can be counts, costs, hours, weights, percentages, votes, or any other parts of the same total.
- Click Plot Pie Chart to generate the interactive chart.
- Hover over slices to inspect labels, values, and percentages, then use Download PNG to save the chart for a report or presentation.
Reference
What the results mean
slice label
The category name shown in the pie chart legend and hover label.
slice value
The numeric contribution used to calculate the size of one segment.
total value
The sum of all slice values entered in the chart.
percentage
Each slice value divided by the total value, multiplied by 100.
part-to-whole relationship
A comparison where every category is part of the same complete total.
Assumptions and limits
Before using the chart
- Pie charts work best for a small number of meaningful categories, typically two to six slices.
- Values should represent parts of the same total, such as one budget, one survey question, one bill of materials, or one project time allocation.
- Avoid pie charts when categories can be negative, when values do not share a common total, or when precise comparisons between many similar values are required.
- For many categories or close numeric comparisons, a bar chart is usually easier to read.
- Use verified data before including the chart in formal reporting.
FAQ
Pie Chart Generator questions
Can I add more slices?
Yes. Use Add Slice to add as many rows as needed, although pie charts are easiest to read with a small number of categories.
Does the pie chart generator calculate percentages?
Yes. The tool sums the entered values and displays each slice as a percentage of the total. You can hover over the chart to inspect labels, values, and percentages.
Do my values need to add up to 100?
No. You can enter raw values such as costs, counts, hours, or quantities. The generator calculates the total and converts each slice into a percentage automatically.
Can I download the pie chart?
Yes. Use Download PNG to save the chart image for reports, presentations, notes, or documentation.
When should I use a bar chart instead of a pie chart?
Use a bar chart when you have many categories, negative values, very similar values, or when precise side-by-side comparison matters more than showing part-to-whole share.
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