Calculateur de Rapports
Simplifiez des rapports, comparez-les et mettez-les à l'échelle
Ratio Calculator
Simplify and solve ratios
Simplify a ratio A:B to its lowest terms
Divide both A and B by their GCDWhat is a Ratio Calculator?
A Ratio Calculator is a math tool that helps you compare two or more quantities and express their relationship in a simple form. A ratio shows how much of one thing there is compared to another. Ratios are commonly written using a colon, such as 3:2, or as a fraction, such as 3/2.
Ratios are used in everyday life and many fields: cooking recipes (2 cups flour to 1 cup sugar), mixing solutions (1 part concentrate to 4 parts water), map scales, financial comparisons, and geometry. They are especially useful when you need to scale something up or down while keeping the same relationship between values.
A ratio calculator can simplify ratios, create equivalent ratios, and help solve 'missing value' problems (often called proportion problems). It saves time and reduces mistakes when working with large numbers or decimals.
How to Use This Ratio Calculator
- Enter the ratio values -- Input the two (or more) numbers you want to compare (example: 24 and 36)
- Choose an option (if available) -- such as simplify ratio, find equivalent ratio, or solve for missing value
- Click 'Calculate' -- the calculator processes the ratio
- Review the simplified ratio -- example: 24:36 becomes 2:3
- Use the result -- apply the ratio for scaling recipes, mixing, comparing quantities, or solving proportions
Tips:
- Ratios work best when the values represent the same type of measurement (e.g., both in grams, both in dollars)
- If you use decimals, the calculator may convert them to a simplified whole-number ratio
- If a ratio is used to scale something (like a recipe), make sure you multiply or divide both parts by the same factor
Ratio Formulas
Ratio Simplification
To simplify a ratio a:b, divide both numbers by their greatest common divisor (GCD):
Simplified = (a / gcd(a,b)) : (b / gcd(a,b))
Example: a = 24, b = 36
gcd(24, 36) = 12
24:36 → (24/12):(36/12) = 2:3
Equivalent Ratios
Multiply or divide both parts by the same number k:
(a:b) → (a × k : b × k)
2:3 × 5 → 10:15
Proportions (Missing Value)
A proportion compares two equal ratios: a/b = c/d
Solve using cross-multiplication:
a × d = b × c
If d is unknown: d = (b × c) / a
Example Calculations
Example 1: Simplify a Ratio
Input: 24:36
GCD: gcd(24, 36) = 12
Calculation: 24 ÷ 12 = 2, 36 ÷ 12 = 3
Result: 2:3
Example 2: Create an Equivalent Ratio
Input: 3:8, scaled by 4
Calculation: 3 × 4 = 12, 8 × 4 = 32
Result: 12:32 (simplifies back to 3:8)
Example 3: Recipe Scaling (Real-World Use)
Setup: A drink mix uses a ratio of 1:5 (concentrate : water)
Problem: If you have 3 cups of concentrate, how much water?
Calculation: 1 part → 5 parts, so 3 parts → 3 × 5 = 15 parts
Result: 15 cups of water
Example 4: Solve a Proportion (Missing Value)
Problem: Solve for x in 2/3 = 10/x
Cross-multiply: 2x = 3 × 10 = 30
Solve: x = 30 ÷ 2 = 15
Result: x = 15
Frequently Asked Questions
What's the difference between a ratio and a fraction?
A fraction represents a part of a whole (3/4). A ratio compares two quantities (3:4). Ratios can be written as fractions, but they often represent comparisons rather than parts.
How do I simplify a ratio?
Divide both parts by their greatest common divisor (GCD). For example, 18:24 simplifies to 3:4 because gcd(18,24) = 6, and 18/6 = 3, 24/6 = 4.
Can ratios include more than two numbers?
Yes. You can have ratios like 2:3:5, often used to compare three quantities (for example, ingredient proportions). Simplification usually divides all terms by their common factor.
What does a ratio like 1:5 mean?
It means for every 1 unit of the first quantity, there are 5 units of the second. For example, 1 cup of concentrate to 5 cups of water.
What is a proportion, and why is it useful?
A proportion states that two ratios are equal (a/b = c/d). It's useful for scaling, converting, and solving for unknown values in real-world situations like recipes, maps, and unit conversions.
Want to add this ratio calculator to your website? Get a custom embed code that matches your site's design and keeps visitors engaged.
Qu'est-ce qu'un rapport ?
Un rapport exprime la relation entre deux quantités. Écrit sous la forme A:B (ou A/B), il indique combien de fois une valeur contient l'autre. Les rapports sont partout : les formats d'écran (16:9), les mesures de recettes (1:2 de farine pour le sucre), l'effet de levier financier dans les investissements et les échelles de cartes (1:50 000) qui permettent de mesurer des distances réelles sur le papier.
Cette calculatrice simplifie les rapports à leur forme irréductible en divisant les deux parties par leur plus grand commun diviseur (PGCD). Elle compare également deux rapports pour vérifier s'ils sont équivalents, et met un rapport à l'échelle pour correspondre à n'importe quel total — vous savez ainsi immédiatement quelle quantité de chaque partie il vous faut lorsque la valeur cible change.
Comment utiliser la calculatrice de rapports
- Entrez les deux valeurs du rapport — A et B.
- Sélectionnez l'opération : simplifier, comparer ou mettre à l'échelle.
- Pour la mise à l'échelle, entrez le total cible que vous souhaitez atteindre.
- Cliquez sur Calculer pour voir le résultat simplifié ou mis à l'échelle instantanément.
Formules et référence
Simplifier A:B — diviser les deux par PGCD(A, B)
Exemple : 12:8 → PGCD = 4 → 3:2
Rapports équivalents — produit en croix
A:B = C:D si A × D = B × C
Mise à l'échelle vers le total T :
Partie A = (A / (A + B)) × T
Partie B = (B / (A + B)) × T
Partie par rapport au tout :
A / (A + B) = fraction du total pour AUn rapport A:B est équivalent à la fraction A/(A+B) comme part du total, ou A/B comme comparaison directe entre les deux parties.
Exemples résolus
Simplifier 15:10
PGCD(15, 10) = 5. Diviser les deux côtés : 15 ÷ 5 = 3, 10 ÷ 5 = 2. Rapport simplifié : 3:2. Pour chaque 3 unités de A, il y a 2 unités de B.
Mélanger ciment et sable dans un rapport 3:5 pour 40 kg au total
Total de parts = 3 + 5 = 8. Ciment = (3/8) × 40 = 15 kg. Sable = (5/8) × 40 = 25 kg. Vérification : 15 + 25 = 40 kg. ✓
Format d'image 1920:1080 simplifié
PGCD(1920, 1080) = 120. Diviser les deux : 1920 ÷ 120 = 16, 1080 ÷ 120 = 9. Résultat : 16:9 — le format écran large standard utilisé sur presque tous les écrans modernes.