# Long Addition Calculator

URL: https://speedycalculator.com/calculators/math/long-addition/
Last updated: 2026-10-30

> The long addition calculator adds two numbers in columns, the way you would on paper, showing the carries and the aligned decimal points.

## Inputs

- First number (A)
- Second number (B)

## Results

- Sum
- Column addition
- Number of carries

## Formula

```
Add each column from right to left; write the units digit and carry the tens digit
```

## Explanation

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.

## 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.

## FAQ

**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.


## Sources

- [OpenStax – Prealgebra 2e](https://openstax.org/details/books/prealgebra-2e)
- [OpenStax – Contemporary Mathematics](https://openstax.org/details/books/contemporary-mathematics)