Doubles facts and doubles plus one: how to teach them

Quick answer

Doubles facts are additions where both numbers are the same, like 4 + 4 = 8. They're easy to remember because they're everywhere: two hands make 5 + 5 = 10. Once doubles are solid, near doubles follow: 6 + 7 is double 6 plus one, so 13. Common Core lists this strategy in 1st grade (1.OA.C.6), and all one-digit sums are known by the end of 2nd grade.

Doubles are the addition facts kids tend to learn first and remember longest. Once they're automatic, they unlock a whole set of harder facts through near doubles, and they lead naturally to even numbers, halves and the 2 times table. Here is how to teach them in a way that sticks.

All the doubles facts, with everyday examples

There are only ten doubles from 1 + 1 to 10 + 10. Pairing each one with something your child can see or touch makes it much easier to remember.

Look at the answers: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20. They go up by 2 each time, which is skip counting by 2s. Kids who can count by 2s already “know” the answers; they just need to match each one to its double.

When kids learn doubles

Small doubles like 2 + 2 and 3 + 3 often appear in kindergarten. In the Common Core standards, used by most states, 1st graders add within 20 using strategies that include known sums: the official example is 6 + 7 = 6 + 6 + 1 = 12 + 1 = 13 (1.OA.C.6). By the end of 2nd grade, children should know all sums of two one-digit numbers from memory (2.OA.B.2) and connect doubles to even numbers (2.OA.C.3). Your state or school may differ.

How to teach doubles, step by step

Step 1: Build doubles with objects

Make two equal towers of LEGO bricks, or two equal rows of crackers, and push them together. Say it in math words: “4 and 4 make 8.” A small mirror is a fun extra: place 3 blocks against it and your child sees 6.

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Step 2: Match each double to a picture

Use the table above, or let your child invent their own pictures. An egg carton is perfect for 6 + 6 because the two rows of 6 are right there.

Step 3: Say them in order, then mixed up

Start by saying the doubles in order (“1 + 1 is 2, 2 + 2 is 4…”). Once that's easy, mix them up: “What's 7 + 7? What's 3 + 3?” Mixed questions show whether your child really remembers each fact or is just following the pattern. Short, frequent practice works better than one long session, and missed facts should come back a day or two later; that idea, called spaced practice, is one of the recommendations in a U.S. Institute of Education Sciences practice guide.

Step 4: Use doubles to solve near doubles

Near doubles are facts where the two numbers are next-door neighbors, like 6 + 7 or 8 + 7. There are two ways to use a double:

• Doubles plus one: double the smaller number and add 1. 6 + 7 = 6 + 6 + 1 = 13.
• Doubles minus one: double the bigger number and take away 1. 6 + 7 = 7 + 7 − 1 = 13.

Another one: 8 + 7. Double 7 is 14, and 8 is one more than 7, so 8 + 7 = 15. Or double 8 is 16, minus 1 is 15. Some children also like doubles plus two for numbers two apart: 5 + 7 = 5 + 5 + 2 = 12. Another way to see 5 + 7: move 1 from the 7 to the 5, and it becomes 6 + 6 = 12.

Doubles, even numbers and halves

Every double is an even number. That's the 2nd grade definition of even in Common Core: a number you can write as the sum of two equal numbers, like 8 = 4 + 4 (2.OA.C.3). Try it with 7 objects: you can't split them into two equal groups without one left over, so 7 is odd.

Doubles also work backwards as halves. If 8 + 8 = 16, then half of 16 is 8, and 16 shared fairly between 2 people is 8 each. That is a child's first taste of division, and it links to the 2 times table: 2 × 8 is just 8 + 8.

Doubles also make neat fact families with only two facts: 8 + 8 = 16 and 16 − 8 = 8.

Common mistakes (and how to help)

• Confusing “double” with “add 2.” A child says double 6 is 8. Build 6 + 6 with blocks and compare it to 6 + 2.
• Doubling the wrong number in a near double. For 8 + 7 they double 8 and add 1, getting 17. Ask, “Which number did you double? Is the other one bigger or smaller?”
• Mixing up 6 + 6 and 7 + 7. Anchor them to pictures: an egg carton is 12, two weeks is 14.
• Counting on fingers for every double. That's fine at first. Keep practicing with pictures and games so recall gradually replaces counting.

Doubles facts games

• Doubles war. Use a deck of cards with face cards removed (aces = 1). Each player flips a card and doubles it. The bigger double wins both cards.
• Doubles dice. Roll one die and say its double. Roll two dice: if they match, the player who calls out the double first scores a point.
• Doubles memory. Make cards with a double (7 + 7) and cards with answers (14). Turn them face down and find the matches.
• Mirror hunt. Put a few toys in front of a mirror and ask how many you see altogether.
• Doubles spotting. On walks or in the kitchen, look for things that come in two equal groups.

Practice problems

The first five are doubles, the next five are near doubles (ask which double helped), and the last two connect to halves and even numbers.

Doubles and near doubles (with answers)

1. 3 + 3 = ?
2. 6 + 6 = ?
3. 7 + 7 = ?
4. 8 + 8 = ?
5. 9 + 9 = ?
6. 4 + 5 = ?
7. 6 + 7 = ?
8. 7 + 8 = ?
9. 8 + 9 = ?
10. 5 + 7 = ?
11. Half of 14 = ?
12. Is 18 even or odd?

Show answers

Doubles are one of several fact strategies; the full sequence is in our guide on how to teach addition, and the next strategy to learn is often make ten. For grade-by-grade goals, see our 1st grade and 2nd grade checklists, and print extra practice from our addition worksheets.

Frequently asked questions

What are doubles facts in math?

Doubles facts are addition facts where a number is added to itself, such as 3 + 3 = 6 or 9 + 9 = 18. The ten basic doubles run from 1 + 1 = 2 to 10 + 10 = 20. Children usually learn them early because they are easy to picture and remember, and they become anchors for other facts.

What is the doubles plus one strategy?

Doubles plus one is a way to solve facts where the two numbers are next to each other, like 7 + 8. Double the smaller number (7 + 7 = 14) and add 1 more, because 8 is one more than 7. So 7 + 8 = 15. It turns a harder fact into a known double plus one.

What is the near doubles strategy?

Near doubles is the umbrella name for using a double to solve a fact that is close to it. It includes doubles plus one (6 + 7 = 6 + 6 + 1 = 13), doubles minus one (6 + 7 = 7 + 7 − 1 = 13) and sometimes doubles plus two (5 + 7 = 5 + 5 + 2 = 12). Common Core mentions this kind of easier, known sum in 1st grade.

What grade learns doubles facts?

Many children meet small doubles like 2 + 2 in kindergarten. In the Common Core, 1st graders use known facts such as doubles to add within 20 (1.OA.C.6), and by the end of 2nd grade children should know all sums of two one-digit numbers from memory (2.OA.B.2). Your state or school may differ.

How do I help my child memorize doubles facts?

Connect each double to a picture (two hands for 5 + 5, an egg carton for 6 + 6), practice a few minutes a day, and play quick games like doubles war or doubles dice. Bring back the ones your child misses a day or two later rather than drilling all ten at once.

Are all doubles facts even numbers?

Yes. When you add a whole number to itself, the answer is always even, because it can be split into two equal groups. That is exactly how Common Core describes even numbers in 2nd grade: an even number can be written as a sum of two equal addends, like 8 = 4 + 4 (2.OA.C.3).

Sources

• Common Core State Standards: Grade 1, Operations & Algebraic Thinking — CCSSI
• Common Core State Standards: Grade 2, Operations & Algebraic Thinking — CCSSI
• Organizing Instruction and Study to Improve Student Learning (practice guide) — Institute of Education Sciences, What Works Clearinghouse

Written by The Mathing Team for parents and teachers. Grade expectations follow the Common Core State Standards for Mathematics; your state or school may sequence skills a little differently.