Long Addition Calculator
Add numbers in columns and see every carry — the written method, step by step.
Column addition works right to left.
How the long addition calculator works
Column addition works right to left. Add each column; if the total reaches ten, write the units digit and carry the tens digit into the next column left.
The carry is the whole idea, and it only works because each place is worth ten times the one to its right. Ten ones become one ten, ten tens become one hundred — the same exchange at every step.
Formula: add each place, carrying any excess of ten into the next place left
Worked examples
| Inputs | Total | Note |
|---|---|---|
| 4837 + 926 + 1508 | 7271 | 7271 |
| No carrying needed | 579 | 579 |
| Carrying all the way | 1000 | 1000 |
FAQFrequently asked questions
What is long addition?
The written column method: line the numbers up by place value and add each column, carrying where a column reaches ten.
What does carrying mean?
Exchanging ten of one place for one of the next place left — ten ones for a ten, ten tens for a hundred.
Why line up the right-hand digits?
Because that aligns the place values. Ones must sit above ones, or the columns add unlike quantities.
Can I add decimals this way?
Yes, by lining up the decimal points, though this page handles whole numbers.
Why start from the right?
Because a carry moves leftward, so working right to left means each column is final once written.
Where these figures come from
- NIST Digital Library of Mathematical Functions — reference definitions for elementary and special functions
- Wolfram MathWorld — definitions and formulas for every topic on this page
- NIST/SEMATECH e-Handbook of Statistical Methods — the statistical formulas (mean, variance, z, confidence intervals, sample size)
- Common Core State Standards — Mathematics — the terms and methods taught in US schools
Last checked: September 2026. Formulas are fixed by mathematics and do not change with tax years or regulations.