Keep the fraction or use a decimal? Avoid premature rounding
A reduced fraction keeps a ratio exact. A short decimal display may only approximate that ratio, especially in repeated calculations.
Fraction calculator →Reduce without changing the value
Dividing numerator and denominator by the same nonzero common factor leaves a fraction unchanged. For 42/56, the greatest common divisor is 14, giving 3/4. The reduced fraction tells the same story using smaller integers. Use the GCD tool to find that factor or add 0/1 in the fraction calculator to simplify a single fraction through the two-input interface.
Some decimals never terminate
One third is 0.333… with infinitely repeating threes. Rounding it to 0.33 and then multiplying by 3 gives 0.99, whereas the exact fraction gives 1. A reduced denominator containing only factors 2 and 5 produces a terminating decimal; other prime factors produce a repeating decimal. Keep the fractional result for intermediate work when exact arithmetic is important.
Match precision to the task
A fraction is not automatically more accurate than the measurement that produced it. If a length was measured only to the nearest centimetre, presenting a long exact-looking ratio does not improve that measurement. Enter integer numerators and nonzero integer denominators, keep signs consistent, and round the final decimal to the precision the task requires. For a ratio involving three quantities, use a proportional model rather than treating every fraction as a measurement.
Try the calculators
- Fraction calculator
Add, subtract, multiply and divide fractions.
- GCD and LCM calculator
Find the greatest common divisor and least common multiple of two integers.
- Ratio calculator
Find d in a:b = c:d from a, b and c.