Adding within 20
In 1st grade, children learn to add within 10 quickly and accurately, to count on from the larger number, and to make ten or use a double for harder sums within 20.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
Try these with your child
These are real questions from our 1st grade practice. Tap the speaker to hear one read aloud, or the light bulb for a hint, and talk about the answer together.
Question 1 of 3
Mia has 7 toy cars. Her friend gives her 2 more toy cars. How many toy cars does Mia have now?
- 8
- 10
- 9
Why this matters
Quick, comfortable adding is one of the first big wins in your child's math life. Sums like 8 + 6 turn up inside adding 28 + 6 next year and inside multiplying in 3rd grade. And once they come easily, your child's attention is free for the new idea in a problem. You'll see it in board games, at snack time, and whenever someone asks how many there are in all.
Up next is subtracting within 20, which uses the same facts in reverse.
Where kids can get stuck
- Counting by ones for every sum, which works for 3 + 2 but gets slow and error-prone for 9 + 7.
- Splitting a number wrongly when making ten, turning 8 + 5 into 8 + 2 + 2 and getting 12 instead of 13.
- Adjusting a double the wrong way, so 7 + 8, thought of as 8 + 8 = 16, comes out as 17 instead of 15.
How you can help
- Make a ten-frame, a box of ten spaces, from an egg carton with two cups cut off. Put in 8 small objects, then 5 more, and ask your child to fill the ten spaces before counting what spills over.
- Practice doubles in the car with a call-and-answer game: you say "6 and 6," they say "12." Once they know a double, ask about the near double, like 6 and 7.
- Play a quick card game with cards 1 to 10: flip two cards, and the first to say the total keeps them. Talk about how you figured out the harder ones.
Want a little more? Watch the kid-friendly video below together, or try Bobby's Math Club for free practice that adapts to your child.
Kid-friendly explanation
Questions parents ask
Why is my child learning to add with strategies instead of memorizing facts?
Strategies like making ten and using doubles help your child understand how numbers work, so a forgotten fact can be rebuilt. If 8 + 6 slips their mind, they can think 8 + 2 is 10, and 4 more is 14. These strategies also build the mental math needed for bigger numbers. Memorizing still comes, and it's easier because the facts are connected.
What does it mean to add fluently within 10?
It means your child can find sums within 10, like 7 + 3 or 4 + 5, quickly and accurately without a long counting process. They might know some instantly and use a fast strategy for others, such as starting at 6 and counting on 2. Fluency doesn't mean timed drills. It means comfort and accuracy with these small sums.
What if my child is still counting on fingers in 1st grade?
That's common for many 1st graders, especially for sums past 10. Fingers are a tool, and children set them aside as faster strategies take hold. Encourage your child to start from the larger number, then try making ten with small objects. If your child understands what the numbers mean, speed tends to come with steady practice.
Make learning math fun
Bobby's Math Club turns 1st grade math practice into something fun to do together.
- Unlimited practice, completely free
- A few minutes a day, at just the right level
- Level-ups, badges, and a cheer for every win
Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.
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Join the clubNote for teachers: This skill is covered by Common Core math standard 1.OA.C.6: “Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 - 4 = 13 - 3 - 1 = 10 - 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 - 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).” Learn how Bobby's Math Club can help your students grow. (Common Core 1.OA.6)