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- Adds, subtracts, multiplies and divides decimals exactly.
- Shows the paper method: lining up points, counting decimal places, moving the point.
- Avoids computer rounding errors, so 0.1 + 0.2 gives exactly 0.3.
- Lets you choose how many decimal places to show for division.
How to use the decimal calculator
Enter the first decimal
For example 2.5.
Pick the operation
Add, subtract, multiply or divide.
Enter the second decimal
For example 1.25.
Read the answer and steps
The working shows exactly how to do it by hand.
How to work with decimals
Adding and subtracting
Line up the decimal points
Fill empty places with zeros
Add or subtract as whole numbers, then put the point back
Multiplying
Ignore the points and multiply the whole numbers
Count the total decimal places in both numbers
Place the point that many places from the right
2.5 has 1 decimal place and 1.25 has 2, so the answer has 3.
Dividing
Move the point in the divisor to make it a whole number
Move the point in the dividend the same number of places
Divide as usual
Example 1: multiplying decimals
2.5 × 1.25
- 25 × 125 3,125
- Decimal places 1 + 2 = 3
- Answer 3.125
A second example: 0.04 × 0.3 = 12 with 3 places, which is 0.012.
Example 2: adding and subtracting
Line up the points.
- 0.1 + 0.2 0.3
- 5.6 − 2.75 5.60 − 2.75 = 2.85
Many calculators and spreadsheets show 0.1 + 0.2 as 0.30000000000000004. This calculator works with exact digits instead.
Example 3: dividing decimals
7.5 ÷ 0.25
- Move both points 2 places 750 ÷ 25
- Answer 30
1 ÷ 3 never ends, so it is rounded: 0.333333 to 6 decimal places.
Where a decimal calculator helps
Homework
Check decimal multiplication and division and see the paper method.
Shopping and money
Multiply prices and quantities to the cent.
Measurements
Add and subtract lengths and weights with decimals.
Unit prices
Divide a price by an amount to compare value.
Turn a decimal into a fraction with the decimal to fraction calculator, round your answer with the rounding calculator, or compare prices with the unit price calculator.
Decimal calculator FAQ
How do you multiply decimals?
Multiply as if there were no decimal points, then count the decimal places in both numbers and place the point that many places from the right.
How do you divide by a decimal?
Move the decimal point in the divisor to make it a whole number, move the point in the dividend the same number of places, then divide.
Why does 0.1 + 0.2 not equal 0.3 on some calculators?
Computers store decimals in binary, which causes tiny errors. This calculator works with the exact digits, so it gives 0.3.
How do you add decimals?
Line up the decimal points, fill gaps with zeros, add as whole numbers, then bring the point straight down.
How many decimal places are shown?
Exact answers show all their digits. For division that does not end, choose 2, 4, 6 or 10 places.
Can I use negative decimals?
Yes. The usual sign rules apply, so −1.5 × 2 = −3.