Scaling a recipe up or down by weight
Scaling a recipe is multiplication by a single factor: the new serving count divided by the original. Double a recipe and every ingredient is multiplied by 2; take a recipe written for 6 and make it for 4 and the factor is 4 ÷ 6, or about 0.667. The arithmetic is simple — the place people slip is doing it in their head, ingredient by ingredient, and rounding inconsistently along the way.
Weight scales cleanly where volume does not. A cup of flour can vary by 20% depending on how it's scooped, so multiplying cups compounds that error every time you scale. Grams don't have that problem — 250 g is 250 g whether you're halving or tripling. This calculator scales a single ingredient amount from one serving count to another and keeps the unit consistent, so you can run each line of a recipe through it and trust the totals.
One caution: not everything scales linearly. Ingredient weights, yes — but bake time, pan size, and leavening don't simply double when you double a batter. A cake scaled to twice the volume needs a larger pan (see the pan-size converter) and a longer, gentler bake, not the same tin crammed full. Use the scaler for the ingredients, then think separately about the vessel and the oven.
Eggs are the other awkward case. They come in whole units, so a factor of 1.5 leaves you needing one and a half eggs. The clean fix is to weigh them: a large egg is roughly 50 g out of the shell, so scale by weight and beat a spare egg to measure out the fraction you need. The same trick rescues any ingredient that doesn't divide neatly.
Worked example
A recipe calls for 320 g of flour and serves 6; you need it to serve 10.
- Factor = new ÷ old = 10 ÷ 6 ≈ 1.667
- Flour = 320 g × 1.667 ≈ 533 g
→ 533 g of flour. Run every other ingredient through the same 1.667 factor.