How to use (3 steps)
- Choose add or subtract, then type the two numbers. Commas and full-width digits are accepted.
- Expand “Options” to keep trailing zeros or show guide lines. Teacher mode adds carry and borrow cues so the active column is easier to follow.
- Click Calculate or just change an input to update the result, layout, and step-by-step narration. Use Auto play or the arrows to walk through each column.
Shortcuts: Alt+S share, Alt+L copy LaTeX, Alt+[ previous step, Alt+] next step.
Examples
Long addition/subtraction layout
How it’s calculated
Teacher notes
- Start by showing that the same place values stay in one vertical line before you talk about any carrying or borrowing.
- Pause on the first carry or borrow column and compare the column just before it and just after it so the change has a clear reason.
- Use examples with borrowing across 0 or with aligned decimals when you want to surface the places where students usually hesitate.
Print more practice for this skill
Pick the worksheet set that matches the operation you are teaching, then print it for class, homework, or quick review.
FAQ
How do I align decimals?
The tool pads the shorter decimal with zeros so both numbers share the same decimal length. Turn on the dotted decimal guide to see the alignment.
When do carry and borrow happen?
A carry appears when a column adds to 10 or more; a borrow appears when the top digit is smaller than the bottom digit plus any previous borrow.
How do you borrow through zeros?
We walk left until we find a non-zero digit, reduce it by one, and turn any zeros in between into 9s. Each borrow is shown in the steps.
Can I enter commas or full-width numbers?
Yes. Commas are removed, and common full-width digits and punctuation are normalized before checking the number.
How can I check whether the answer is correct?
The “Check your answer” panel under the result flips the operation back: addition becomes subtraction, and subtraction becomes addition. Even when decimals or trailing zeros look different, the checking relationship stays the same.
- Percentage Calculator Convert parts, whole, and percentages with explanations.
- Fraction Calculator Reduce fractions, mixed numbers, and perform operations.
- Long Division (with steps) See every division step with repeating decimals highlighted.