Subtracting Fractions Calculator

First fraction (A)

Whole (optional)

Numerator

Denominator

Example formats: 3/4 → W=0, N=3, D=4 · -1 1/2 → W=-1, N=1, D=2

Second fraction (B) (will be subtracted)

Whole (optional)

Numerator

Denominator

Use positive denominators only. Negative values can go in the whole or numerator fields.

Subtracting Fractions – Quick Cheat Sheet

Mixed to improper: w n/d → (|w|·d + n) with sign. Example: 2 1/3 = 7/3, -1 1/2 = -3/2.
Find LCD: Use the least common multiple of denominators.
Scale numerators: A = a·(LCD/a_d), B = b·(LCD/b_d).
Subtract: A − B = (A_scaled − B_scaled) / LCD.
Reduce: Divide numerator & denominator by GCD. Keep denominator positive.
Back to mixed: n/d → w = floor(|n|/d), r = |n| % d with sign on w (or n if w=0).
Negatives: Put the negative on the whole or numerator; denominators should be positive.

Notes & edge cases