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Fraction Calculator

Add, subtract, multiply, or divide two bounded integer fractions and inspect the exact reduced result, GCD, and rounded decimal display.

Use this result well

Inputs that matter
Two bounded whole-number numerators, two positive whole-number denominators, and one selected add/subtract/multiply/divide operation
Output to expect
Sign-normalized exact reduced fraction, unreduced fraction, integer GCD and rounded decimal approximation
How it works
Uses exact safe-integer cross-products or reciprocal multiplication and reduces by integer GCD; it rejects zero denominators and division by a zero-valued second fraction
  • Put any sign in the numerator and preserve the original units or measurement meaning outside the fraction notation.
  • Treat the displayed decimal as rounded; use the exact reduced fraction when exactness matters and verify application-specific rounding separately.

Choose your path

Built around the job you need to finish

Apply one selected arithmetic operation to two bounded integer fractions and return a sign-normalized exact reduced result plus an explicitly rounded decimal display.

Student checking fraction arithmetic

See the exact result and the reduction step rather than only a decimal.

Enter two whole-number numerator/positive-denominator pairs, choose the operation and inspect the unreduced result and GCD.

Can reproduce the answer and distinguish exact fraction from rounded decimal.

Craftsperson combining signed measurements

Handle negative numerators and improper results consistently.

Put the sign in the numerator, keep denominators positive and review the sign-normalized result.

Receives one canonical fraction without a negative denominator.

Reviewer testing boundary errors

Prevent decimal fraction components, zero denominators and division by a zero-valued fraction.

Use bounded whole values and read the explicit error when the divisor fraction equals zero.

No invalid operation disappears into a blank result or floating-point GCD artifact.

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Reference & details

How it works

Exact Integer Fraction Model

Every numerator and denominator must be a bounded safe whole number. Denominators are positive, while signs belong in numerators.

Fraction = integer numerator ÷ positive integer denominator

Operation and Reduction

Addition and subtraction use cross-products, multiplication uses component products, and division multiplies by the reciprocal. The result is reduced by integer GCD.

Reduced result = unreduced numerator/GCD ÷ unreduced denominator/GCD

Exact Result, Rounded Display

The fraction result stays exact within the safe-integer input bounds. The separate decimal approximation is rounded for display and should not replace the fraction when exactness matters.

Updated: August 2026

Example Scenarios

A student checks 3/4 + 1/3 and audits both the unreduced cross-product and GCD reduction.

Fraction A: 3/4Operation: +Fraction B: 1/3

13/12 exact; 1.08333333 rounded decimal

A craftsperson subtracts a larger positive fraction and retains the negative sign in the numerator.

Fraction A: 1/4Operation: Fraction B: 3/4

−1/2 exact

A reviewer attempts to divide by 0/5 and receives an explicit error rather than a blank or infinite result.

Common Mistakes to Avoid

Entering decimal components and expecting exact fraction GCD behavior

Use whole-number numerator and denominator components. Convert a terminating decimal to a fraction first when exact arithmetic is required.

Treating the rounded decimal as the exact answer

Retain the reduced fraction for exact work; the decimal display may round a repeating expansion.

FAQ

The exact engine uses bounded integers and stores the sign in the numerator, producing one canonical sign-normalized fraction instead of equivalent negative-denominator forms.

The engine forms exact cross-products, combines the numerators over the product denominator, then divides both result components by their integer greatest common divisor.

A zero-valued second fraction is a zero divisor. Its reciprocal would require division by zero, so the operation is explicitly rejected.

The reduced fraction is exact within the documented integer bounds. The decimal is a rounded display and may terminate or repeat depending on the denominator.

The arithmetic is unit-neutral. Keep the original unit and quantity meaning attached and apply domain-specific precision or rounding after reviewing the exact fraction.

About Fraction Calculator

Enter two whole-number numerators, two positive whole-number denominators, and one operation to get a sign-normalized exact reduced fraction.