Online Rule of Three Calculator

Need to solve proportion calculations quickly? Our rule of three calculator solves automatically and shows the result.

---

What is the rule of three?

The rule of three is a simple mathematical method used to solve proportionality problems between quantities. It can be simple (involving 3 values to find the 4th) or compound (with several related quantities).

👉 Example: If 2 apples cost $4, how much do 5 apples cost? The answer comes from the rule of three: $10.

---

How to use the rule of three calculator

1. Fill in the three known values.
2. Leave the field for the value you want to calculate blank.
3. Click Calculate.

✅ The tool automatically shows the proportional value.

---

Practical use examples

• Personal finance: calculate discounts and adjustments.
• Cooking recipes: adjust ingredient quantities.
• Studies: solve math exercises quickly.

---

Frequently Asked Questions (FAQ)

What is direct proportion?

When one quantity increases, the other also increases in the same proportion.

And inverse proportion?

When one quantity increases, the other decreases in the same proportion.

---

Tips and curiosities

• The rule of three is the basis of many everyday calculations.
• Knowing how to set up the proportion correctly is the secret to avoiding errors.

---

➡️ Solve your proportion right now with the calculator above!