Column addition is how we add multi-digit numbers by hand. Lining up the decimal points and keeping track of carries are the two skills that make it reliable.
How to use the Long Addition Calculator
- First number (A)
- Second number (B)
Everything is calculated in your browser, so results appear instantly and nothing you type is sent to a server.
How it works
The numbers are padded so their decimal points line up, then each column is added from right to left. A carry of 1 is written above the next column whenever a column sum reaches 10.
Formula
Add each column from right to left; write the units digit and carry the tens digit
Worked example
Inputs — First number (A): 987.65; Second number (B): 45.9.
Results — Sum = 1033.55; Column addition = 111
987.65
+ 45.90
─────────
1033.55; Number of carries = 4.
Key terms
- Carry
- A digit moved to the next column when a column sum exceeds 9.
Frequently asked questions
Why line up the decimal points?
So that digits with the same place value are added together.
What is carrying?
When a column adds to 10 or more, the tens digit moves to the next column.
How do I add more than two numbers?
Add them two at a time, or stack them all and add each column.
Can I add negative numbers this way?
Work out the sign first; the calculator handles signed numbers directly.