The formula is straightforward: Scaling Factor = Target Servings ÷ Original Servings. If you want to double a recipe that serves 4, your scaling factor is 2. Scaling the same recipe to serve 20 gives a factor of 5. From there, you multiply every ingredient by that number — and for most ingredients in most recipes, that’s the whole job done.

The problem is that a few ingredients don’t behave proportionally at larger volumes. Leavening agents are the most critical: too much baking powder or baking soda causes over-rising followed by collapse, leaves a bitter metallic aftertaste, and changes the texture of the finished product. This doesn’t dramatically affect a simple doubling, but it becomes a real problem at ×3 and above. Salt and spices also overwhelm at full multiplication — the palate doesn’t scale linearly the way a measuring cup does.

Scaling cooking recipes (soups, stews, stir-fries, sauces) is more forgiving than scaling baking recipes. In cooking, you can taste and adjust at every stage. In baking, the chemistry is set before anything hits the oven. Most of the nuance in this guide applies specifically to baking — if you’re scaling a soup or a marinade, multiply everything and taste at the end.

Use this table when converting common measurements across the most frequent scaling factors. The first column is the original amount in the recipe. The remaining columns show the exact scaled amount. For any measurement not listed, multiply the original by your scaling factor and use the nearest practical measure.

Four ingredient types need adjustment when scaling beyond ×1.5. Applying the standard multiplier to all of them produces noticeably worse results in baked goods — and at large scale, it can ruin the dish entirely.

These are the most important scaling exception. Both agents release carbon dioxide gas chemically — and the reaction isn’t proportional to volume. Larger batches retain gas better and their dough provides more structural support, so less leavening is needed per unit. Too much baking powder creates a sharp metallic taste and causes the centre to collapse after an initial over-rise. The rule: use 75% of the calculated leavening amount when scaling at ×2 or above.

Salt perception is non-linear. A dish serving 20 doesn’t need 5× the salt of one serving 4 — the palate simply doesn’t work that way. Start with 75% of the calculated salt amount, taste before serving, and add more in small increments. This is especially important for soups and braises where salt concentrates as the liquid reduces during cooking.

Strong spices — chilli, cumin, cloves, cinnamon — can overpower a dish when fully multiplied at large scale. Start at 75% of calculated and taste before adding more. Vanilla extract follows the same rule: at ×3 or ×4, full multiplication makes it taste sharp and artificial. Dried herbs are slightly more forgiving than spices but still benefit from the same conservative starting point.

The same formula works in reverse. Halving a recipe uses a factor of 0.5 — multiply every ingredient by 0.5, or simply divide by 2. Scaling to a third uses 0.33. The leavening rule still applies: for a half batch, use about 60% of the original leavening amount (not 50%), since very small quantities of baking powder lose effectiveness when reduced too aggressively.

The practical challenge when scaling down is measuring small amounts precisely. ⅛ teaspoon is the smallest increment on most measuring spoon sets. For anything below that — a pinch of saffron, a very small amount of a strong spice — switching to grams on a kitchen scale is the most accurate approach. A scale that reads in tenths of a gram handles quantities that volume measures simply can’t.