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Cooking Maths

Maths hiding in cooking: recipe ratios

Keep the same taste by matching quantities in a recipe.

Quick answer

Maths hiding in cooking: recipe ratios means using multiplication and division to change a recipe so it makes more or fewer servings while keeping the same taste. You can make a recipe for 4 people, then double it for 8 people, or halve it for 2 people, and it still tastes the same.

Learning outcome

By the end of this page, you will be able to change a recipe to make more or fewer servings using simple maths – like doubling or halving ingredients – and keep the same taste. Success signs:
  • You can multiply or divide recipe ingredients by 2, 3, or 4.
  • You can work out how much of each ingredient you need for a different number of people.
  • You can explain why recipes need the same ratios to taste the same.
  • You can solve a simple recipe problem with a new number of servings.

Why this matters

Maths in cooking helps you make the right amount of food for your family or friends. When you're cooking, you don’t always want to make just one serving – maybe you want to make enough for a party or share with a friend. If you change the number of servings, you need to change the ingredients in the right way so it still tastes great. This is where ratios come in. Ratios help you keep the same taste by keeping the same relationship between ingredients. In school, you’ll learn about ratios in maths too. In cooking, you’re using ratios without even realising it. This is a great way to see how maths helps you in real life!

How it works

Let’s look at how ratios work in cooking. A recipe has ingredients in a certain ratio. If you want to make more or fewer servings, you have to change the amounts in the same ratio. Here’s how it works step by step:
  1. Look at the original recipe and see how many people it serves.
  2. Decide how many people you want to serve.
  3. Find the ratio – how much of each ingredient you need per person.
  4. Use multiplication or division to change the amounts.
Let’s try an example. If a recipe makes 4 servings and you want 8, you need to double everything. If you want 2 servings, you halve everything.

Examples you can see

Let’s look at a real recipe for pancakes. This recipe makes 4 pancakes. Original recipe (serves 4):
  • 2 cups of flour
  • 1.5 cups of milk
  • 1 egg
  • 1 tablespoon of sugar
  • 1 teaspoon of salt
Now, let’s say you want to make 8 pancakes (double the recipe). You need to double every ingredient: Doubled recipe (serves 8):
  • 4 cups of flour
  • 3 cups of milk
  • 2 eggs
  • 2 tablespoons of sugar
  • 2 teaspoons of salt
What if you only want 2 pancakes (half the recipe)? Then you halve everything: Halved recipe (serves 2):
  • 1 cup of flour
  • 0.75 cups of milk
  • 0.5 egg
  • 0.5 tablespoon of sugar
  • 0.5 teaspoon of salt
You can even make a recipe for 12 pancakes by tripling the original recipe. Or make 1 pancake by dividing everything by 4.

Try it as a mini adventure

Adventure: The Great Cake Swap You are helping your family bake a cake for a party. The recipe makes 8 cakes, but you only need 4. You have to figure out how to make half the recipe without making a mess. You start with:
  • 2 cups of sugar
  • 3 cups of flour
  • 4 eggs
  • 1 cup of butter
  • 1 teaspoon of vanilla
You need to make only 4 cakes. What do you do?
  1. First, you notice the recipe makes 8 cakes, so you need to halve everything.
  2. Then you divide each ingredient by 2.
So, the new recipe for 4 cakes is:
  • 1 cup of sugar
  • 1.5 cups of flour
  • 2 eggs
  • 0.5 cup of butter
  • 0.5 teaspoon of vanilla
Great job! You’ve saved ingredients and made the right amount of cake.

Common mistakes

  • Mistake: Adding ingredients instead of multiplying or dividing.
    Why it happens: Confusing addition with multiplication.
    Fix: Think of doubling as "2 times" the amount, not "2 more".
  • Mistake: Forgetting to change all ingredients.
    Why it happens: Not reading the full recipe carefully.
    Fix: Check each ingredient and make sure it’s changed in the same way.
  • Mistake: Mixing up "more" and "less" when changing recipes.
    Why it happens: Not thinking about whether to multiply or divide.
    Fix: If you want more servings, multiply. If you want fewer, divide.
  • Mistake: Not using the same ratio for all ingredients.
    Why it happens: Thinking that one ingredient can be different.
    Fix: Keep the same relationship between all ingredients.

Parent and carer guide

Cooking with your child is a fun way to learn maths. Here’s how to help:
  • Start with simple recipes, like pancakes or cookies.
  • Ask your child to help you double or halve the recipe.
  • Let them measure ingredients. This helps them understand quantities.
  • Encourage them to explain why they multiplied or divided.
  • Make it a game – like a cooking challenge to make a recipe for 6 people from one that makes 3.
  • Don’t worry if they make a mistake – it’s part of learning!
You can also use everyday situations to practice:
  • Buying ingredients for a recipe
  • Sharing food with friends or family
  • Adjusting a recipe for a different number of people
Remember, cooking is a great way to show your child that maths is useful and fun!

Practice questions

  1. If a recipe makes 6 servings and you want to make 3 servings, what do you do to each ingredient?
  2. A recipe uses 2 cups of flour for 4 people. How much flour do you need for 8 people?
  3. If you halve a recipe that makes 10 servings, how many servings will you have?
  4. A recipe uses 3 eggs for 6 servings. How many eggs do you need for 12 servings?
  5. You have a recipe for 5 people. How much of each ingredient do you need if you want to make 15 servings?
Answers:
  1. Halve each ingredient.
  2. 4 cups of flour.
  3. 5 servings.
  4. 6 eggs.
  5. Triple each ingredient (because 15 ÷ 5 = 3).

FAQ

What is a recipe ratio?

A recipe ratio is the relationship between the amounts of ingredients in a recipe. It tells you how much of each ingredient to use to make a certain number of servings.

Why do we need to keep the same ratios in recipes?

If you change the ratio of ingredients, the food will taste different. Keeping the same ratios makes sure the recipe still tastes the same, no matter how many people you’re cooking for.

Can I use decimals in recipes?

Yes! You can use decimals when you halve or quarter ingredients. For example, half of 1 cup is 0.5 cups, and half of 0.5 cups is 0.25 cups.

How can I practice recipe ratios at home?

You can practice by changing the number of servings in a simple recipe, like cookies or pancakes. Try doubling or halving the recipe and see if it still tastes the same.

What if I don’t have measuring cups?

You can still practice with everyday items like spoons or bowls. For example, 1 cup is about 4 tablespoons. You can estimate and practice ratios that way.