Long Multiplication Calculator
This long multiplication calculator works step by step: enter two numbers and it shows every partial product with the carries and the sum. 247 × 38 gives 9,386 – from 247 × 8 = 1976 and 247 × 30 = 7410. Decimals and negative numbers work too.
Source: Wikipedia – Schriftliche Multiplikation. Updated: .
How it is calculated
In long multiplication you split the second factor into its digits, multiply the first factor by each digit and add the partial products, each shifted one place further left. If a single product reaches 10 or more, you write down the units digit and carry the tens digit.
Example: 247 × 38
- First 8 × 247: 8 × 7 = 56 → 6, carry 5; 8 × 4 + 5 = 37 → 7, carry 3; 8 × 2 + 3 = 19. Partial product: 1976.
- Then 3 × 247 (the digit is in the tens place, so add a zero): 741, shifted 7410.
- Sum: 1976 + 7410 = 9386.
With decimals and negative numbers
For decimals, multiply without the decimal point first and put it back at the end so the result has as many decimal places as both factors together: 12.5 × 0.04 = 125 × 4 = 500 with three decimal places, which is 0.5. When the factors have different signs the result is negative. The calculator shows each intermediate step with its carries and a table of the partial products – good for practice at school and for checking homework. The reverse operation is covered by the long division calculator, and for learning the basic facts there is the times tables trainer.
Frequently asked questions
How do you do long multiplication?
Multiply the first number by each digit of the second in turn (from the right), handle the carries, shift each partial product one place further left and add them all up.
How do you do long multiplication with decimals?
Leave out the decimal point at first and multiply like whole numbers. The result then has as many decimal places as both factors together.
What is a carry?
When a single product exceeds 9, you write only the units digit and add the tens digit to the next single product.
Why do you shift the partial products to the left?
Each digit of the second factor has a place value: the tens digit counts ten times, the hundreds digit a hundred times. Shifting (or appended zeros) reflects that.
How can I check the answer?
With an estimate: 247 × 38 is about 250 × 40 = 10,000, and the result 9,386 is close.
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