Pie chart maker

What the pie chart maker does

A pie chart shows how a whole is shared between categories. Each slice is the same fraction of the circle as its value is of the total. On this page you pick a data set (Favorite sport, A school day, Car colors in the lot, or My own) and use the plus and minus buttons to set each value from 0 to 99. You can have from 2 to 5 categories, and in My own you can type the names and the title.

The table shows each value as a fraction of the total in lowest terms, a percent and an angle, and the readout says how many degrees each 1 is worth. Show switches between the pie, a matching bar chart, or both side by side. New challenge asks you to make one slice a set size, given as a percent, an angle or a fraction.

Why build pie charts

Drawing a pie chart by hand means finding each value as a fraction of the total, then turning that fraction into degrees out of 360. Doing it here, children can change one value and see every slice shift, because changing one part changes the whole. That is the key idea: a pie chart shows proportions, not amounts. The bar chart view makes the contrast clear. Bars compare amounts; slices compare shares.

Common mix-ups

• Thinking a bigger slice always means a bigger number. Two pie charts with different totals can't be compared slice by slice.
• Using 100 instead of 360. Percents are out of 100; angles are out of 360 degrees.
• Forgetting that the slices must add up to the whole. All the percents add to 100% and all the angles to 360°, apart from rounding.
• Expecting a change to one value to leave the other slices alone. Every slice depends on the total.

A 10-minute pie chart lesson

• Choose A school day. Ask: a whole day is 24 hours and a circle is 360°, so how many degrees is one hour? (15°)
• Ask for the angle of the sleep slice before reading the table.
• Press New challenge and solve two challenges.
• Switch to Both and ask which chart shows that School is bigger than Play more clearly.
• Double every value and ask why the pie looks the same.

Where it fits by grade

• Grades 5 and 6: practice fractions of a total and percents. Common Core does not name pie charts, but finding a percent of a quantity is standard 6.RP.A.3c.
• Grade 4 and up: angles are measured in degrees, with a full turn of 360° (4.MD.C.5), which is what the angle column uses.
• Grades 7 and 8: use pie charts to compare proportions and discuss when a pie chart is a good choice.
• England: Year 6 interprets and constructs pie charts and uses them to solve problems, and Key Stage 3 continues with pie charts for categorical data.

Learning more

Percentages, fractions and angles are skills on Eurekami's skill map, and Daily Practice brings them back when they start to fade. For older students, Exam Prep includes GCSE Maths practice papers, and the AI tutor asks guiding questions when a problem is tricky.