Math
Long Addition and Subtraction Calculator
Enter two numbers and choose add or subtract to see column arithmetic exactly as it is taught: numbers stacked with the ones (or decimal points) aligned, carries written above the columns for addition, borrows marked for subtraction, and one sentence per column explaining what happened.
Negative numbers and decimals follow the standard rules.
Goes on top. Up to 18 digits; decimals and negatives allowed.
Goes underneath.
Try an example
Result
Answer
—
- Carries or borrows
- —
- Check
- —
Student quick launch
Grade planning, algebra checks, and formulas students reach for most.
Study path
Use this calculator with
Follow these when you want the formula behind the answer, a short lesson, or nearby tools in the same topic.
What the column method calculator solves
Column addition and subtraction work one place value at a time, starting from the ones. Addition regroups when a column total reaches 10 (carrying); subtraction regroups when the top digit is too small (borrowing). This page draws the columns, marks each carry or borrow, and explains every column in words so you can compare it with your own work.
Decimals
Line up the decimal points, not the right-hand edges. Add zeros so both numbers have the same number of decimal places, do the column arithmetic, then bring the decimal point straight down. 12.5 + 3.75 becomes 12.50 + 3.75 = 16.25.
Negative numbers
| Expression | Rewrite | Column work | Answer |
|---|---|---|---|
| 8 + (-3) | 8 - 3 | subtract sizes | 5 |
| -8 + 3 | -(8 - 3) | subtract sizes, keep the bigger sign | -5 |
| -8 - 3 | -(8 + 3) | add sizes, keep negative | -11 |
| 8 - (-3) | 8 + 3 | add sizes | 11 |
How to use it
- Choose Add or Subtract and enter the two numbers.
- Read the answer and the tableau: carries appear above the columns, borrows as rewritten digits.
- Open Show the work for a sentence about each column, then use the check line to confirm.
How to read the answer
Each column step tells you the two digits, any carry or borrow coming in, and what was written. A carry means a column total was 10 or more; a borrow means the top digit needed 10 more. For subtraction with mixed signs, the answer takes the sign of the number with the larger size. The check line runs the inverse operation and should land back on the first number.
Common mistakes and edge cases
- Lining up decimals on the right edge instead of on the decimal point: 12.5 + 3.75 is 16.25, not 4.00.
- Forgetting to add a carry into the next column.
- Subtracting the smaller digit from the larger regardless of position: 52 - 37 is 15, not 25.
- Borrowing across zeros incorrectly: 1000 - 1 needs the borrow to ripple through each zero.
- Subtracting a negative as if it were positive: 8 - (-3) = 11.
Worked examples
Addition with three carries
4758 + 967 = 5725.
Answer
5725
Subtraction with borrowing
4758 - 967 = 3791.
Answer
3791
Subtracting across zeros
1000 - 1 = 999.
Answer
999
Decimals
12.5 + 3.75 = 16.25 after lining up the points.
Answer
16.25
Smaller minus larger
967 - 4758 = -3791.
Answer
-3791
Subtracting a negative
8 - (-3) = 11.
Answer
11
Cancelling to zero
5 + (-5) = 0.
Answer
0
Frequently asked questions
What does carrying mean in addition?+
When a column adds to 10 or more, you write the ones digit and move the tens digit to the next column on the left. 8 + 7 = 15 → write 5, carry 1.
What does borrowing mean in subtraction?+
When the top digit is smaller than the bottom digit, take 1 from the column to the left (worth 10 in the current column). 5 - 7 becomes 15 - 7 = 8 after borrowing, and the left digit drops by 1.
How do I subtract across zeros?+
Borrow from the first nonzero digit to the left and let the borrow ripple through: in 1000 - 1, the 1 becomes 0 and each 0 becomes 9, giving 999.
How do I add decimals in columns?+
Line up the decimal points, pad the shorter number with zeros, add normally, and bring the decimal point straight down.
How do I add a negative number?+
Adding a negative is subtracting: 8 + (-3) = 8 - 3 = 5. With two negatives, add the sizes and keep the negative sign: -8 + (-3) = -11.
How can I check my answer?+
Use the inverse: after subtracting, add the result back to the number you subtracted; after adding, subtract one addend from the sum.
About this calculator
- Written by
- mathcheck editorial team
- Last reviewed
- September 4, 2026
Method
- Uses the values entered by the user and stable formulas documented on the page.
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Last updated: September 4, 2026