Ratio and Proportion Calculator

Find the unknown value in A : B = C : D, or simplify any ratio to its lowest terms.

Мгновенный результат Работает в браузере

Proportion — leave the unknown field empty:

:
=
:

Leave exactly one field (A, B, C or D) empty to find the unknown. Fill all four to check whether the proportion holds.

Simplify a ratio:

:

Examples

ProblemSolution
3 : 4 = ? : 8? = 6
5 : ? = 10 : 6? = 3
? : 7 = 3 : 21? = 1
2 : 3 = 6 : ?? = 9

Formula

A / B = C / D
A × D = B × C

A : B = C : D means A/B = C/D, so A × D = B × C (cross-multiplication). To find D: D = B × C / A.

Как использовать?

  1. 1
    Enter three valuesFill in any three of the four fields A, B, C, D. Leave the unknown blank.
  2. 2
    Click CalculateThe missing value is found via cross-multiplication: A × D = B × C.
  3. 3
    Simplify a ratioEnter X and Y in the lower section to reduce the ratio X : Y to its lowest terms.

Частые вопросы

What is a proportion?
A proportion states that two ratios are equal: A/B = C/D. Cross-multiplying gives A × D = B × C, which is used to find any missing value.
How do I simplify a ratio?
Divide both numbers by their Greatest Common Divisor (GCD). For example 12:8 — GCD is 4, so 12/4 : 8/4 = 3 : 2.
What is the difference between a ratio and a proportion?
A ratio compares two quantities (e.g. 3:4). A proportion states that two ratios are equal (e.g. 3:4 = 6:8). This calculator handles both.

Ratios and Proportions Explained

A ratio compares two numbers: 3:4 means for every 3 units of A there are 4 units of B. A proportion says two ratios are equal: 3:4 = 6:8. Cross-multiplication (A × D = B × C) lets you find any missing term.

Real-World Uses

Ratios appear in cooking (scale recipes), maps (1:50 000), construction (mix ratios), finance (price-to-earnings), and school exams worldwide.

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