Read

Addition Facts Up to 20

Addition facts up to 20 are the basic sums, like 3 + 2 or 9 + 8, that Math 1 students memorize for quick mental math. This lesson covers counting on, doubles, near doubles, and making ten strategies for fast, accurate recall.

Introduction

Addition facts up to 20 are the basic sums that combine two numbers, from small pairs like \(2 + 3\) to larger combinations like \(9 + 8\), where the total never goes past 20. Knowing these facts by heart, without stopping to count everything from scratch, is one of the biggest building blocks of early math. Once these facts feel automatic, harder skills like adding three numbers or regrouping become much easier.

What Are Addition Facts Up to 20?

An addition fact is any sum of two whole numbers, such as \(6 + 5 = 11\) or \(9 + 9 = 18\). There are many possible pairs that add up to a number between 0 and 20, and the goal of this topic is to recognize these sums quickly instead of recalculating them every time. Strong recall of these facts also makes subtraction easier, since every addition fact has a matching subtraction fact.

Key Strategies for Learning Addition Facts to 20

Instead of memorizing every fact in isolation, it helps to group them by strategy. A few of the most useful approaches are described below.

Counting on: Start at the larger number and count up by the smaller number, such as counting 9, 10, 11 to solve \(9 + 2\). This method is explored in more depth in using counting to add digits up to 20.
Doubles and near doubles: Facts like \(5 + 5 = 10\) or \(8 + 8 = 16\) are easy to remember, and they help with nearby facts. For example, since \(6 + 6 = 12\), then \(6 + 7\) must be one more, or \(13\).
Making ten: Break one addend apart so the first two numbers make exactly 10, then add what is left. This turns \(9 + 4\) into \(10 + 3\), which is much easier to picture.
Using 5s and 10s: Many facts are simpler when one number is already a 5 or a 10, such as \(10 + 7 = 17\). This idea is covered further in adding numbers with 5s and 10s.

Using a Number Line to Add

A number line is a helpful visual for counting on. To solve \(9 + 4\), start at 9 and make four jumps forward, landing on 13.

Counting on from 9 to 13 shows that 9 + 4 = 13.

For adding with a series of jumps of one, or for adding three or more numbers on the same line, see using number line to add up to 20.

Making Ten: A Visual Strategy

The making ten strategy is especially useful once one addend is close to 10. To add \(9 + 4\), split the 4 into \(1 + 3\). Adding the 1 to the 9 makes a full ten, and the remaining 3 is easy to add on top.

Making ten turns 9 + 4 into 10 + 3, which equals 13.

When Sums Need Regrouping

Some addition facts up to 20, especially those with two-digit totals like \(8 + 9 = 17\), connect directly to regrouping once numbers get bigger than single digits. A solid grasp of these facts makes that next step much smoother, and it is covered in detail in addition with regrouping up to 20.

Fact Families for Addition to 20

Every addition fact belongs to a fact family that also includes a matching subtraction fact. Seeing all four related facts together reinforces the relationship between addition and subtraction.

Addition fact 1	Addition fact 2	Subtraction fact 1	Subtraction fact 2
\(8 + 5 = 13\)	\(5 + 8 = 13\)	\(13 - 8 = 5\)	\(13 - 5 = 8\)
\(6 + 9 = 15\)	\(9 + 6 = 15\)	\(15 - 9 = 6\)	\(15 - 6 = 9\)

Practice Tips

Short, frequent practice works better than one long session. Mix strategies as facts come up: try counting on for sums close together, doubles for matching numbers, and making ten whenever one addend is 8 or 9. Speaking the fact aloud, such as saying "nine plus four equals thirteen," also strengthens memory alongside written practice.

Related lessons

Math 1