3-Digit Addition Worksheets

3-digit addition worksheets to print (PDF)

These 3-digit addition worksheets show what the generator prints: a page with regrouping, a page without regrouping, a horizontal page for mental math and the answer key. Click a picture for the PDF, or use the generator above to make a new set.

About 3-digit addition

3-digit addition uses exactly the same steps as 2-digit addition, one more column to the left. Grade 2 children add within 1,000 (2.NBT.B.7), and grade 3 children do it fluently (3.NBT.A.2), as the Common Core standards for grade 3 number and operations in base ten describe. These worksheets start with no regrouping, then move to regrouping in the ones or tens, and finally problems where both columns carry.

How to add 3-digit numbers

Take 489 + 312:

1. Ones: 9 + 2 = 11. Write 1, carry 1 ten.
2. Tens: 8 + 1 + 1 carried = 10. Write 0, carry 1 hundred.
3. Hundreds: 4 + 3 + 1 carried = 8.
4. The answer is 801.

Check with an estimate: 500 + 300 = 800, so 801 makes sense.

3 digit addition worksheets: how many problems carry?

The number of carries decides how hard a 3-digit addition problem is. If the generator chooses two 3-digit numbers at random, the problems divide like this. The counts are exact, from all 810,000 ordered pairs of 3-digit numbers, and use the rule that a column carries when the digits and the carry-in add up to 10 or more:

Only 13% of the pairs need no regrouping, so a worksheet with 3-digit addition without regrouping needs the “No carrying” setting. Most problems have one or two carries, and 16% carry in all three columns. 60% of the answers have four digits, because the hundreds column carries into the thousands.

3 digit addition without regrouping: the easy start

3 digit addition without regrouping is the best way to begin, because no column adds up to 10 or more. Take 342 + 215: the ones are 2 + 5 = 7, the tens are 4 + 1 = 5 and the hundreds are 3 + 2 = 5, so the answer is 557. The generator’s “No carrying” setting makes a worksheet of problems like this, and about 13% of all pairs of 3-digit numbers are of this kind.

Adding 3 digit numbers: the three steps

When you are adding 3 digit numbers, three steps cover every case. First line up the digits, with the ones under the ones. Then add each column from the right, and write a carry above the next column when a column adds up to 10 or more. Finally check the answer with an estimate. The worksheets follow the same order, and the answer key shows every step.

3 digit addition with regrouping: carrying through the columns

The hardest 3-digit addition problems carry all the way. In these five problems, the ones carry into the tens, and the tens carry into the hundreds, so the answer has a 0 in the ones and tens columns, which trips up many children:

When a carry meets a column that already adds up to 9, the result is 10 and another carry. Children who see this pattern with problems such as 497 + 303 find 3 digit addition with regrouping much less scary.

Three digit addition worksheets: 20 practice problems with answers

These 20 problems come from the generator’s rule for 3-digit addition, so they are a fair sample of what the worksheets contain. The table shows how many carries each problem has, so a teacher can pick the easier ones for younger children:

Estimate first when adding 3-digit numbers

Rounding each number to the nearest hundred gives a quick estimate of the answer. In 3-digit addition, the estimate will never be more than 100 away from the exact sum, because each number is rounded by at most 50:

An estimate catches the most common mistakes, such as a forgotten carry, which changes the answer by 10 or 100. The rounding worksheets practice this skill.

3-digit addition word problems

Word problems link 3-digit addition to real situations, and they ask children to say what the answer counts. These four stories need one addition each:

Common mistakes in 3-digit addition

The mistakes in 3-digit addition are mostly about carrying. This table shows what the wrong answers look like for four problems, so a teacher can see which step the child missed:

Write the carried digit small above the next column and cross it out when it has been used. Grid paper, where each digit has a box, helps with the other common mistake, which is to line up the digits wrongly.

A five-day plan for 3-digit addition

Most children need about a week of short sessions to become secure in 3-digit addition. This plan goes from review to word problems. When a child is ready, move on to 4-digit and 5-digit addition:

Tips

• Label the columns H, T and O at the top of the page for the first few days.
• Use the grid paper worksheet so every digit sits in its own box.
• When a 0 appears in the answer after carrying, check that the carried 1 went into the next column.