DIY Cost Tools
Fraction Calculator
Math calculator
Fraction Calculator
Add, subtract, multiply, or divide two fractions and see a reduced fraction, decimal, and mixed result.
Add, subtract, multiply, or divide fractions
Enter integer numerators and nonzero integer denominators. The calculator performs the selected operation, moves any negative sign to the numerator, and reduces the result using the greatest common divisor.
Fraction rules
Subtract: a/b − c/d = (ad − bc)/bd
Multiply: a/b × c/d = ac/bd
Divide: a/b ÷ c/d = ad/bc
Worked example
For 3/4 + 2/3, multiply across the opposite denominators: (3 × 3 + 2 × 4) / (4 × 3) = 17/12. The result is already reduced and can also be written as 1 5/12 or approximately 1.4167.
Understanding simplification
A fraction is in lowest terms when the numerator and denominator share no whole-number factor greater than one. Dividing both by their greatest common divisor changes the appearance but not the value.
- When adding or subtracting, create a common denominator before combining numerators.
- When multiplying, multiply numerators together and denominators together.
- When dividing, multiply by the reciprocal of the second fraction.
- A denominator cannot be zero, and division by a zero-valued fraction is undefined.
Frequently asked questions
Why do fractions need a common denominator for addition?
The denominator identifies the size of each part. Parts must have the same size before their counts can be added or subtracted.
Can the calculator use negative fractions?
Yes. Enter a negative numerator or denominator. The reduced result presents any negative sign with the numerator.
What if the answer is greater than one?
The result remains available as an improper fraction and is also shown as a mixed form when applicable. Both represent the same value.
How to get a dependable result
- Use nameplate ratings or manufacturer specifications when they are available.
- Keep every input in the unit shown beside its field.
- Treat calculated values as planning estimates; real equipment, batteries, and conductors have losses, tolerances, and operating limits.
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Sources and review notes
The calculator uses exact integer arithmetic within JavaScript’s safe numeric range and standard fraction-operation rules.
Last reviewed September 2026. Results are educational estimates and do not replace product instructions, electrical codes, engineering review, or professional advice.