Subtraction Facts Up to 20

Subtraction facts up to 20 are the basic subtraction problems that use numbers from 0 to 20, such as \( 9 - 4 = 5 \) or \( 18 - 9 = 9 \). Knowing these facts quickly, without stopping to count on fingers, is one of the most important skills in early math. Once a student can recall these facts automatically, subtracting bigger numbers, solving word problems, and even learning multiplication later on all become much easier.

Every subtraction fact has three parts: the number you start with (the minuend), the number you take away (the subtrahend), and the number left over (the difference). In the fact \( 14 - 6 = 8 \), 14 is the minuend, 6 is the subtrahend, and 8 is the difference. Subtraction facts up to 20 simply means the starting number, or minuend, is no greater than 20.

Before jumping into memorization, it helps to fully understand what the subtraction symbol means. If that idea still feels shaky, review understanding the subtraction sign first.

One of the easiest ways to solve a subtraction fact is to start at the minuend and count backward by the subtrahend. For \( 13 - 4 \), start at 13 and count back four numbers: 12, 11, 10, 9. The answer is 9.

Counting back works well for small subtrahends, but it becomes slower and less reliable as the gap between numbers grows. For step-by-step practice with this method, see counting forward to subtract up to 20, and for a visual approach try using a number line to subtract up to 20.

Every subtraction fact is connected to an addition fact through a fact family. If \( 8 + 5 = 13 \), then it must also be true that \( 13 - 8 = 5 \) and \( 13 - 5 = 8 \). Since most students learn addition facts first, this connection turns a new subtraction fact into something already familiar.

Using this strategy, a student who already knows \( 6 + 9 = 15 \) can instantly answer both \( 15 - 6 = 9 \) and \( 15 - 9 = 6 \) without needing to count at all.

Some subtraction facts follow simple patterns that are worth memorizing on their own:

• Subtracting zero never changes the number: \( n - 0 = n \). For example, \( 17 - 0 = 17 \). This rule is explored further in subtracting with the number zero.
• Subtracting a number from itself always gives zero: \( n - n = 0 \). For example, \( 12 - 12 = 0 \).
• Subtracting 1 is the same as saying the number right before it, such as \( 20 - 1 = 19 \).

Example 1: Solve \( 16 - 7 \) by counting back. Starting at 16 and counting back 7: 15, 14, 13, 12, 11, 10, 9. So \( 16 - 7 = 9 \).

Example 2: Solve \( 11 - 4 \) using a fact family. Since \( 4 + 7 = 11 \), it follows that \( 11 - 4 = 7 \).

Example 3: Solve \( 20 - 0 \). By the zero rule, subtracting zero leaves the number unchanged, so \( 20 - 0 = 20 \).

Fast, accurate recall of subtraction facts up to 20 comes from repeated practice, not just from learning the strategies once. Mixing quick drills with visual tools like number lines and fact triangles helps reinforce the connections between numbers. Once these facts feel automatic, applying them to larger numbers becomes far easier, as covered in subtracting with digits up to 20.

Related lessons

• Math 1