What Is Long Addition? (Interactive Widget)

Use this interactive widget to see a step-by-step explanation of long addition.

This is a randomly generated long-addition sum.

See similar widgets on long subtraction, long multiplication, and long division. Long addition involves writing the numbers to be added one underneath another, so the digits are in columns. The numbers are added a column at a time.

Many numbers of any length (including decimals) can be added in this way.

1

Write the numbers you wish to add, one underneath the other.

2

Add up the numbers in the right-most column.

3

Check if the answer from the previous Step is 9 or less:

• If Yes, write the number below the column (between the lines) and move to Step 4.

• If No, the answer will have two digits.

Write the digit on the right underneath the column (between the lines).

Write the digit on the left underneath the column to the left of the current column (below the two lines).

This is carrying. Move to Step 4.

4

Move to the column to the left. Add up the numbers in this column, including any numbers below the two lines.

5

Go to Step 3 and repeat until all columns have been added.

A Real Example of How to Do Long Addition

Question 1

Write the numbers you wish to add, one underneath the other. 2

Add up the numbers in the right-most column. 7 + 4 = 11

3

Check if the answer from Step 2 is 9 or less:

No. 11 is not 9 or less.

• If No, the answer will have two digits. • Write the digit on the right underneath the column (between the lines). • Write the digit on the left underneath the column to the left of the current column (below the two lines). This is carrying. Move to Step 4.

4

Move to the column to the left.

Add up the numbers in this column, including any numbers below the two lines. 2 + 8 + 1 = 11

5

Go to Step 3 and repeat until all columns have been added.

3

1st repeat

Check if the answer from the previous Step 4 is 9 or less:

No. 11 is not 9 or less.

• If No, the answer will have two digits. • Write the digit on the right underneath the column (between the lines). • Write the digit on the left underneath the column to the left of the current column (below the two lines). This is carrying. Move to Step 4. 4

1st repeat

Move to the column to the left.

Add up the numbers in this column, including any numbers below the two lines. 3 + 1 + 1 = 5

5

1st repeat

Go to Step 3 and repeat until all columns have been added.

3

2nd repeat

Check if the answer from the previous Step 4 is 9 or less:

Yes. 5 is 9 or less.

• If Yes, write the number below the column (between the lines). There are no more columns to the left. All columns have been added.

The solution to 327 + 184 is 511.

Slider

It is possible to add decimals together, as well as to add more than two numbers together.

The slider below shows another real example of how to do long addition.

Open the slider in a new tab