How this calculator works
Reduce the entered values and make each denominator positive. Compare cross products rather than rounded decimal values. Multiplying by positive denominators preserves the direction of the comparison, including when numerators are negative. Equivalent fractions compare equal even when their original numerators and denominators differ.
Formula
For b,d > 0, a/b < c/d if and only if ad < cb. Equality occurs when ad = cb.
Worked example
-1/2 is greater than -2/3 because -3 is greater than -4 after cross multiplication. Also, 1 1/2 equals 6/4 because both reduce to 3/2.
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Frequently asked questions
Why not just compare decimals?
Exact cross products distinguish fractions that would round to the same decimal.
Can denominators be negative?
Yes for a simple fraction. The calculator moves the sign to the numerator before comparing.
Can I compare mixed numbers?
Yes. Enter forms such as 2 1/3 or -1 1/2; the sign applies to the full mixed value.