These days, I find myself immersed in the math of cooking—converting recipe measurements from metric to cups, calculating the volume of loaf tins, and striving for consistency in cake recipes. With a collection of thousands of recipes developed over the years, standardized measurements are often not at hand.
The tools available to home cooks have greatly expanded; metric measures have become the norm (but what’s happening in America?); and the sizes of packaged goods at supermarkets have shifted. Out goes the 284ml pots of double cream, and in comes the 300ml option. Digital scales are now affordable, measuring spoon sets are standard, and the classic dessert spoon measurement is on its way out. Cooking requires both scientific precision and artistic flair, so understanding your ratios is essential. There have been plenty of instances where I got it wrong during recipe testing, and I’m grateful for the process of trial and error!
If you memorize these key formulas, you’ll be well on your way to culinary success.
Pastry Ratios
At catering college, I learned that the basic pastry formula is straightforward: use half the amount of fat (butter, margarine, or lard) to the flour. So, if you weigh your flour, you’ll require half that amount in fat. Conveniently, when butter was mostly available in 250g blocks, you could use a 500g bag of plain flour without additional measuring, making it easy to prepare a large batch that could be frozen.
A splash of liquid, such as water, milk, or beaten egg, may be added to bind the mixture. Increasing the fat content makes the pastry ‘shorter,’ which results in a more challenging dough to handle. This ratio takes you to the realm of shortbread, which consists of two-thirds fat to flour—a content so rich it’s nearly impossible to roll out but results in the finest pastry when pressed into place.
This ratio applies to both sweet and savory pastries. Using 250g of plain flour and 125g of butter is perfect for a 23cm tart crust. This gives you the flexibility to customize your pastry based on the dish at hand. Here are some variations I enjoy:
- Sweet pastry – Incorporate 2 tablespoons of sifted icing sugar with the flour and use a small pinch of salt.
- Almond pastry – Use 200g plain flour, 50g ground almonds, and 2 tablespoons of icing sugar.
- Brown sugar pastry – Mix in 50g of light brown sugar with the flour.
- Parmesan pastry – Add 25g of finely grated Parmesan to the flour.
- Rye pastry – Blend 50g of rye flour with 200g of plain flour.
- Spelt pastry – Incorporate 50g of spelt flour along with 200g of plain flour.
- Wholemeal pastry – Use 75g wholemeal flour and 175g plain flour; you may need a dash of cold water or milk to bind it.
- Devilled pastry – Add 1 tablespoon of mustard powder and a pinch of cayenne.
- Thyme pastry – Mix in 1 tablespoon of finely chopped thyme leaves.
Quiche Equations
Having the perfect pastry allows you to create a quiche, a beloved dish in our cuisine.
The possibilities for quiche fillings are endless, but a savory custard is what binds them all together. For a 23cm quiche, the formula is 3 eggs to 300ml of double cream. As a general guideline for savory custard, use 1 egg per 100ml of double cream (a 1:1 ratio).
This creates a blank canvas for your quiche fillings, but do consider that ingredients with high moisture content, like cherry tomatoes, may dilute the custard and prevent it from setting properly during cooking.
The Crêpe Code
One essential formula I learned from my fantastic Head of Food, Cassie Best, makes every Shrove Tuesday a breeze: the 1–2–3 rule for perfect pancakes—which I fondly remember as 3-2-1 dusty bin (an old Gen X reference!).
The breakdown is simple: 100g plain flour, 2 eggs, and 300ml milk. To create a smooth batter without lumps, whisk the eggs and flour into a thick paste before gradually adding the milk until everything is well mixed.
You can use the batter immediately, but letting it rest for an hour enhances its flavor and texture. This recipe yields about 10–12 small, thin, and lacy pancakes—just how they should be!
Pasta by Numbers
Most dried pasta consists of a simple blend of flour and water, while fresh pasta is typically enriched with egg, giving it a richer flavor and making it a more valuable ingredient. The quantities for homemade pasta dough are refreshingly simple: use a 1:1 ratio—one egg for every 100g of ‘00’ flour.
The egg white hydrates the dough, while the yolk makes it richer. Some recipes even call for just yolks, producing a more vibrant yellow dough. In that case, the measurement becomes 2 yolks for every 100g of ‘00’ flour.
Dressing Logic
The formula for a basic dressing is a 1:3 ratio of acid to oil (1-2-3). If preparing your dressing in a jar or bottle, you can gauge the measurements using your hand—let the vinegar reach your little finger and the oil should come up to your other three fingers.
This base dressing can be enhanced with mustard for added zest and to help with emulsification. Since not all vinegars have the same acidity, you may want to adjust the ratios depending on how punchy you want the dressing—consider using 2 parts acid to 3 parts oil for a stronger flavor.
To the Power of Yeast
The reason why many bakers prefer fresh yeast remains a bit of a mystery, but it’s commonly used, and some traditional recipes call for it. If you’re looking to substitute dried yeast for fresh, simply halve the weight. Conversely, if you wish to switch from dried to fresh (which sometimes raises eyebrows), you’ll need to double the quantity.
To substitute wild yeast (like active sourdough starter) for dried yeast, use a factor of ten. Although wild yeast ferments more slowly, this slower process builds flavor and improves digestion.
The Sponge Cake Calculator
As MasterChef semi-finalist Henry Phillips points out in his social media videos about pasta, the number of eggs required can vary based on their size and weight. Even when a size is specified, egg weights may still differ. For this reason, weighing the eggs before proceeding can often lead to better results.
A noteworthy tip I received from food writer Julie Friend is the secret to the ideal sponge: weigh 4 eggs in their shells, then use an equal weight of self-raising flour, butter, and sugar. No need for any additional milk!
After weighing the eggs, crack them into a bowl and add the equivalent weights of the other ingredients. Whisk until smooth, and you’ll achieve the perfect sponge mixture. Looking back on a sponge recipe I created years ago, I see it aligns with this advice—notably, it calls for 200g of each main ingredient, along with the 4 eggs!
Yorkshire Pudding Solver
One of the early chefs I worked with at Good Food was the proud Yorkshireman Brian Turner MBE. He imparted a golden rule for Yorkshire puddings: maintain equal volumes of flour, eggs, and milk.
My tried-and-true yorkshire pudding recipe is built on this principle. After measuring the volume of a 12-cup Yorkshire pudding tin, I calibrated the ingredients accordingly. Whether you’re making large puddings, small ones, or toads-in-the-hole, ensure equal volumes for your batter for guaranteed results.
Liquid Logic
Today’s scales often have a liquid measurement function. However, different liquids have varying densities, which can make these scales inaccurate unless measuring plain water.
For other liquids like syrups, creams, and honey, it’s best to measure by volume or use grams. Orlando Murrin has compiled helpful weights for 100ml of various liquids:
- 100ml milk weighs 103g
- 100ml double cream weighs 102g
- 100ml maple syrup weighs 135g
- 100ml honey weighs 142g
- 100ml sunflower oil weighs 92g
- 100ml brandy weighs 95g
Gelatine
Historically, recipes have favored leaf gelatine, which requires soaking, draining, and dissolving in warm liquid. In contrast, powdered gelatine only needs to be sprinkled into warm liquid and stirred to dissolve, much like sugar in tea.
Should a recipe call for leaf gelatine, remember that you can easily convert it to powdered with a simple equation: use ½ teaspoon of powdered for each leaf of gelatine.
If you have any food formulas or cooking equations that you’d like to share, feel free to add them in the comments below!
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