How to Teach Three-Digit Addition With Regrouping

Quick answer

To teach 3-digit addition with regrouping, have your child add one column at a time, starting with the ones, then tens, then hundreds. When a column adds up to 10 or more, they regroup: write the ones digit in that column and carry the ten to the next column on the left. Start with problems that don’t need regrouping (like 342 + 125), then move to ones that regroup once or twice. Most kids learn this in 2nd and 3rd grade.

Three-digit addition with regrouping is the same skill as double-digit addition, just one column longer. The routine stays exactly the same (add the ones, then the tens, then the hundreds, and regroup when a column goes past 9), but now kids have to keep track of more digits and sometimes carry more than once. Below is how to teach it step by step, starting without regrouping and then adding it in, along with the mistakes to watch for and practice ideas that work at home.

What is 3-digit addition with regrouping?

Three-digit addition means adding numbers that each have three digits, a hundreds place, a tens place, and a ones place, such as 287 + 465. Regrouping (also called carrying) happens when a column adds up to 10 or more. Since each place can only hold one digit, you keep the ones digit in that column and carry the extra ten to the next column on the left.

This skill maps to Common Core State Standards:

2nd grade (2.NBT.B.7): add and subtract within 1000 using place-value strategies, including regrouping.
3rd grade (3.NBT.A.2): fluently add and subtract within 1000 using strategies and algorithms based on place value.

Most children are ready for 3-digit addition with regrouping once they can handle double-digit addition with regrouping comfortably and understand that a number like 287 means “2 hundreds, 8 tens, and 7 ones.”

Start here: 3-digit addition without regrouping

Always begin with problems where no column adds up past 9. This lets your child learn the three-column routine without the extra step of carrying.

Take 342 + 125:

Stack the numbers so hundreds line up over hundreds, tens over tens, and ones over ones.
Add the ones column first: 2 + 5 = 7. Write 7 in the ones place.
Add the tens column: 4 + 2 = 6. Write 6 in the tens place.
Add the hundreds column: 3 + 1 = 4. Write 4 in the hundreds place.
Read the answer: 467.

The rhythm is the same as two-digit addition, just one more column. Once your child can do five or six of these without pausing, they’re ready for regrouping.

How to teach 3-digit addition with regrouping

Regrouping in three-digit addition works exactly like it does with two digits, but now you might have to regroup more than once. When a column adds up to 10 or more, keep the ones digit and carry the ten to the next column.

Take 287 + 465:

Add the ones column: 7 + 5 = 12. That’s more than 9, so we regroup. Write the 2 in the ones place and carry the 1 above the tens column.
Add the tens column, including the carried ten: 1 + 8 + 6 = 15. Write the 5 in the tens place and carry the 1 above the hundreds column.
Add the hundreds column, including the carried ten: 1 + 2 + 4 = 7. Write 7 in the hundreds place.
Read the answer: 752.

The idea that makes this click is the same as always: 10 ones become 1 ten, and 10 tens become 1 hundred. When you have 10 or more in a column, you bundle ten of them together and that bundle moves to the next column on the left.

Build up slowly: one regroup, then two

Don’t jump straight to problems that regroup twice. Start with problems that regroup in just one column, like 456 + 127 (ones only) or 342 + 180 (tens only). Once those feel easy, move to problems that regroup in two columns, like 287 + 465.

This lets your child practice the carrying routine one step at a time instead of all at once. Five problems that regroup once, then five that regroup twice, is better than ten mixed problems that feel overwhelming.

The 4 mistakes kids make most (and how to fix them)

Fun ways to practice 3-digit addition at home

Practice sticks when it’s short and real. A few ideas:

Car odometer: add the miles from two trips and check the total.
Grocery totals: add the cost of three items before you get to the register.
Card game: each player draws three cards to build a three-digit number, then race to add them.
Score-keeping: add up points across multiple rounds of a board game.
Daily 5: five problems a day beats twenty once a week, because steady repetition is what builds fluency.

Keep sessions to five or ten minutes, and when your child gets one wrong, give a hint and let them try again before you show the answer. That second try is where the learning happens.

How to know your child is ready to move on

Your child has mastered 3-digit addition with regrouping when they can:

Add three-digit numbers without regrouping, quickly and accurately.
Recognize when a column needs regrouping and carry correctly.
Handle problems that regroup in two columns without losing track.
Explain why they carry (“10 ones make 1 ten” or “10 tens make 1 hundred”).
Solve simple word problems that use three-digit addition.

When those feel solid, the natural next steps are three-digit subtraction with regrouping and adding numbers with different numbers of digits (like 287 + 45), which use the very same column routine.

Free Three-digit Addition With Regrouping Worksheet

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The easiest way to give your child practice

For most parents, the hardest part of teaching 3-digit addition with regrouping isn’t the math. It’s coming up with enough of the right problems (starting easy, building up) and keeping your child willing to do them. That’s where Octolearn helps: describe the skill in plain language (“three-digit addition with regrouping”), and it builds a grade-matched practice set with read-aloud support, a hint and a second try on every question, and stars that keep kids coming back.

Frequently asked questions

What grade do kids learn 3-digit addition with regrouping?

Most children learn 3-digit addition with regrouping in 2nd and 3rd grade. The Common Core standard 2.NBT.B.7 covers adding within 1000 using place-value strategies, and by 3rd grade (3.NBT.A.2) kids are expected to add fluently within 1000. Children are usually ready once they can handle double-digit addition with regrouping comfortably.

How do you teach regrouping with three-digit numbers?

Teach the same column routine as two-digit addition: start with the ones, then tens, then hundreds. When any column adds up to 10 or more, keep the ones digit in that column and carry the ten to the next column on the left. Use base-ten blocks or bundled straws so kids can see 10 ones become 1 ten, and 10 tens become 1 hundred.

What is the hardest part of 3-digit addition for kids?

The hardest part is keeping track of multiple carries. When a problem like 287 + 465 needs regrouping in both the ones and the tens columns, kids often forget to add a carried digit or write the two-digit sum in one place. Slowing down and checking each column one at a time helps, and so does saying the carried number out loud before adding.

Should I teach 3-digit addition without regrouping first?

Yes, start with problems like 342 + 125 where no column goes past 9. This lets your child practice the three-column routine (ones, tens, hundreds) without the extra step of carrying. Once they can do five or six of these quickly, introduce regrouping in just one column, then build up to problems that regroup twice.

How can I practice 3-digit addition at home?

Use real numbers from daily life: odometer readings, package weights, grocery totals. Play a card game where each player draws three cards to build a number, then race to add them. Keep practice sessions short (five to ten problems), and when your child makes a mistake, give a hint and let them try again before showing the answer.