Long Addition Calculator — Step-by-Step Column Addition
See exactly how long addition works: enter two whole numbers and get a step-by-step breakdown of each column — ones, tens, hundreds and beyond — showing every carry.
348 + 275
Ones: 8 + 5
Tens: 4 + 7 + 1 (carry)
Hundreds: 3 + 2 + 1 (carry)
Sum
- 1
First addend
348 - 2
Second addend
275 - 3
Sum
348 + 275 = 623
How does this calculator work?
Long addition works column by column from right to left. Each column adds the two digits plus any carry from the previous column. If the column sum ≥ 10, write the units digit and carry 1 to the left. Repeat until all columns are done. Enter two whole numbers to see every step.
Formula
How this is calculated
Long addition is the standard written algorithm taught in primary school. The numbers are aligned on their right-hand (ones) digit, then added column by column from right to left. In each column the two digits plus any incoming carry from the previous column are summed. If the column total is less than 10, that digit is written and the carry resets to 0. If the total is 10 or more, only the units digit is written and 1 is carried to the next column.
The algorithm terminates when all columns have been processed and no carry remains. If a final carry exists after the last column of both numbers, it becomes an extra leading digit of the result — this is why, for example, 999 + 1 = 1000 (three columns of 9+0 generate three carries, each propagating left, eventually producing the leading 1).
This calculator supports whole numbers up to 9,999,999 (seven digits) and shows every intermediate column sum and carry in the step list.
Frequently asked questions
When a column sum is 10 or greater, the tens digit cannot be written in the current column — it is "carried" one position to the left. For example, 8 + 7 = 15: write 5 in the current column and carry 1 to the next column.
Because carries propagate to the left (from the ones column to the tens, from the tens to the hundreds, and so on). Starting from the right lets you handle each carry before it affects the next column, keeping the algorithm simple.
This calculator adds exactly two numbers at a time. To add more, add the first two, then add the result to the third, and so on — each step is its own long-addition problem.
Also known as
TG we-Calculate Editorial Team. (2026). Long Addition Calculator — Step-by-Step Column Addition [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/long-addition-calculator
TG we-Calculate Editorial Team. "Long Addition Calculator — Step-by-Step Column Addition." TG we-Calculate. 2026. https://we-calculate.com/calculator/long-addition-calculator.
TG we-Calculate Editorial Team, "Long Addition Calculator — Step-by-Step Column Addition," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/long-addition-calculator
@misc{wecalculate_long_addition_calculator, title = {Long Addition Calculator — Step-by-Step Column Addition}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/long-addition-calculator}}, year = {2026}, note = {TG we-Calculate} }
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