Can it handle inverse proportions?

This calculator handles direct proportions only. For inverse proportion (like speed and time at constant distance), the formula is X = (A × B) / C.

Give me a real example.

If 5 workers complete a job in 15 days, how long do 8 workers take? Using direct proportion: X = 15 × 8 / 5 = 24 days. (Note: this would actually be inverse proportion — for time and workers use A×B/C = 5×15/8 = 9.375 days.)

Rule of Three Calculator — Proportional Calculation

The Rule of Three Calculator solves proportion problems: if A corresponds to B, what does C correspond to? This simple but powerful technique underlies recipe scaling, unit conversions, map reading, and countless real-world calculations. Enter three known values and instantly find the fourth.

A (known quantity)

B (corresponds to A)

C (new quantity)

How to Use This Calculator

1
Enter A (the known reference quantity).
2
Enter B (what A corresponds to).
3
Enter C (the new quantity you're scaling).
4
Click Calculate — the result is X, what C corresponds to.

Frequently Asked Questions

If A/B = C/X, then X = (B × C) / A. It solves any direct proportion problem where three values are known and you need the fourth.

Related Calculators

📐Ratio Calculator 📐Percentage Calculator 🏠Recipe Scaling Calculator