Long Subtraction Calculator with Steps

Frequently asked questions

What is long subtraction?

Long subtraction is the column method of subtracting numbers: digits are aligned by place value and subtracted one column at a time from right to left, borrowing from the next column whenever the top digit is smaller than the digit below it.

How does borrowing work in long subtraction?

When a top digit is smaller than the digit below it, you borrow 1 from the next column to the left, which adds 10 to the current digit. The column you borrowed from is then reduced by 1. For example, in 1000 - 1, the ones column borrows through every column, turning each 0 into 10 and then 9, giving 999.

What happens if the bottom number is bigger, like 5 - 9?

The result is negative. The calculator computes the reverse subtraction, 9 - 5 = 4, and negates it, so 5 - 9 = -4. The column work shows 9 on top and 5 below, with a note that the answer is negated.

Can this calculator handle very large numbers?

Yes. The column engine works on digit strings of any length, so numbers far beyond normal calculator limits are subtracted exactly, one column at a time.

Why is long subtraction taught in school?

It teaches place value and regrouping concretely: each borrow shows that one ten equals ten ones, one hundred equals ten tens, and so on, which builds the foundation for algebra and mental math.

What is the difference between borrowing and regrouping?

They describe the same action. Borrowing is the traditional word for taking 1 from the next column; regrouping is the modern term emphasizing that the value is reorganized, for example one ten regrouped as ten ones, rather than lent.