All facts · within 20
All the Core Addition and Subtraction Facts to 20
Tap any number in the chart to open that fact: the answer, a picture, a way to work it out, and a game that practices it.
Addition chart, 0 to 10
Find one number on the left and one along the top. Where they meet is the sum.
Reading the chart for subtraction
Each sum on the chart is also a subtraction fact. Find 15 in the row for 7: the column is 8. So 15 − 7 = 8. That's the whole idea behind fact families, and it's why children who are secure with addition find subtraction much easier.
The facts, by strategy
A child doesn't learn 100 separate sums. They learn a few ways of thinking. Here's each group with its first few facts.
| Group | The idea | Try |
|---|---|---|
| Plus 0, 1 and 2 | Count on from the bigger number: 7, then 8, 9. | 1 + 1, 1 + 2, 1 + 3, 1 + 4, 1 + 5, 1 + 6 |
| Doubles | Same number twice: 6 + 6. These are worth knowing by heart. | 3 + 3, 4 + 4, 5 + 5, 6 + 6, 7 + 7, 8 + 8 |
| Near doubles | One more than a double: 6 + 7 is 6 + 6, plus 1. | 3 + 4, 4 + 3, 4 + 5, 5 + 4, 5 + 6, 6 + 5 |
| Make 10 | Pairs that make 10 (7 + 3) are the key to bigger sums. | 3 + 7, 4 + 6, 6 + 4, 7 + 3 |
| Ten plus | 10 plus a number: just put the 1 in front. 10 + 6 = 16. | 3 + 10, 4 + 10, 5 + 10, 6 + 10, 7 + 10, 8 + 10 |
| Bridge through 10 | 8 + 5: make 10 first (8 + 2), then add the rest (3). 13. | 3 + 8, 3 + 9, 4 + 7, 4 + 8, 4 + 9, 5 + 7 |
| Other facts | Use a fact you know: 7 + 4 is 7 + 3 + 1. | 3 + 5, 3 + 6, 5 + 3, 6 + 3 |
Quick quiz
Questions
How many addition facts are there to learn?
There are 121 facts in the addition chart from 0 + 0 to 10 + 10. It's far fewer to learn than that sounds: the turnaround rule halves them, and adding 0, 1 and 2 takes care of many more.
Should children learn addition or subtraction facts first?
Addition first, with subtraction following closely behind. Each subtraction fact is an addition fact seen from the other side. Our guide to teaching subtraction facts shows how.
Is Sumtown really free?
Yes. The whole game plays free in your browser, with no signup, no ads and no time limit. All fourteen mini games are in it. An iPhone app is on its way, and you can read what it will add.
An app is on its way
We're building a Sumtown app for iPhone with the parts that need a real app: offline play for car rides, a town map that remembers how far your child got, and a parent report on every fact. Until then, the whole game is free right here.
Coming soon on theApp Store