Add, subtract, multiply or divide two decimal numbers and get an exact answer — free of the rounding errors ordinary calculators show — with the result also given as a fraction and a percentage.
Results are computed exactly where possible and rounded only to remove the tiny binary rounding errors that decimals cause in ordinary calculators.
Decimals are numbers with a fractional part written after a point, like 0.75 or 3.2. Ordinary calculators sometimes show odd results such as 0.1 + 0.2 = 0.30000000000000004 because of how computers store decimals in binary. This calculator does the arithmetic and then cleans up that tiny error, and it also shows the answer as a fraction and a percentage so you can see it every way.
How the calculation works
Add / subtract / multiply / divide the two numbers, round to remove binary error, then convert: fraction = result over a power of ten, reduced by the greatest common divisor · percentage = result × 100.
Worked example
0.1 + 0.2 = 0.3. As a fraction that is 3/10, and as a percentage it is 30%. For 1.5 × 0.2 = 0.3 as well; and 0.75 on its own is the fraction 3/4, or 75%.
Decimals, fractions and percentages
The three forms describe the same value. A terminating decimal always converts to a fraction with a denominator that is a power of ten, then simplifies — 0.375 is 375/1000, which reduces to 3/8. Multiplying a decimal by 100 gives the percentage, so 0.375 is 37.5%.
Frequently asked questions
Why does 0.1 + 0.2 not equal 0.3 on my calculator?
Computers store decimals in binary, which can't represent 0.1 or 0.2 exactly, so a tiny error appears. This calculator rounds it away to show 0.3.
How do I turn a decimal into a fraction?
Write the decimal over a power of ten matching its decimal places (0.375 = 375/1000), then divide top and bottom by their greatest common divisor.
How do I turn a decimal into a percentage?
Multiply by 100 and add a percent sign. 0.375 becomes 37.5%.
Does it handle negative numbers?
Yes. Enter negatives and the sign carries through the result, the fraction and the percentage.
Written by the CalcPine team · Reviewed for accuracy · Last updated 23 July 2026 · Method: decimal arithmetic rounded to remove binary error; fraction via power-of-ten reduced by GCD.
