To scale a recipe, multiply every ingredient by target servings ÷ original servings — then convert the decimals back into kitchen fractions. Going from 4 servings to 6 means multiplying everything by 1.5, so 2 cups of flour becomes 3 cups and ½ teaspoon of salt becomes ¾ teaspoon. This scaler does the multiplication and the fraction conversion in one step.
The math is easy; the measuring is the hard part
Everyone knows the scaling formula. Almost nobody enjoys applying it to fourteen ingredients while dinner guests are arriving. The arithmetic isn't difficult — it's tedious, and tedium is where mistakes happen. You multiply 1½ cups by 1.5, get 2.25 cups, and stand in the kitchen wondering whether that's 2 cups plus a quarter or plus "a splash."
The second problem is that recipe math produces numbers kitchens can't use. A calculator will happily tell you that you need 0.67 cups of oil. No measuring cup on earth is marked 0.67. Real cooking happens in quarters, thirds, and halves — so a useful scaler has to round every result to the nearest fraction you can actually measure. That's the step most "just multiply it" advice skips, and it's the step this tool is built around.
Paste your ingredients one per line with the amount first ("2 cups flour", "1 1/2 tsp salt", "3/4 cup cocoa"), and the scaler handles whole numbers, decimals, fractions, and mixed numbers like 1 1/2. Anything without a numeric amount — "salt to taste", "a handful of parsley", "2 cloves garlic" (which does have a number, and scales fine) — passes through untouched.
How the scaling works
- Scale factor: target servings ÷ original servings. A factor of 2 doubles the recipe; 0.5 halves it.
- Multiply: each parsed quantity × scale factor.
- Round to kitchen fractions: each result is snapped to the nearest friendly fraction — quarters, thirds, halves, and eighths. So 2.25 cups becomes "2 1/4 cups", 0.67 cups becomes "2/3 cup", and 1.5 teaspoons becomes "1 1/2 tsp".
- Pass through the rest: lines that don't start with a number are returned exactly as written.
Worked example
A pancake recipe serves 4; you're cooking for 6. Scale factor: 6 ÷ 4 = 1.5.
- 2 cups flour → 3 cups
- 1 1/2 cups milk → 2 1/4 cups
- 1/2 tsp salt → 3/4 tsp
- 2 tbsp sugar → 3 tbsp
- 1 egg → 1 1/2 eggs → shown as "1 1/2" (beat one egg and eyeball half of a second, or use 2 small eggs)
Notice the egg: the scaler gives you the honest math (1½ eggs) rather than pretending the problem doesn't exist. For 1½ eggs, beat one egg with half of another — or just use two small eggs and don't overthink it. Pancakes forgive.
What doesn't scale linearly
Three categories deserve a human override after the scaler does its work:
- Leavening. Baking powder, baking soda, and yeast don't scale perfectly — too much leavening in a big batch can taste soapy or make a cake rise fast and collapse. When tripling or more, scale leavening slightly conservatively (about 80% of the computed amount) and let the recipe's structure do the rest.
- Salt and strong spices. Perception of saltiness and heat doesn't double when the recipe doubles. Scale to about 75% of the computed amount, then season to taste. You can always add; you can't subtract.
- Cooking time. A doubled casserole doesn't take twice as long — it takes longer, but how much longer depends on depth, pan, and oven. Start checking for doneness at the original time and go by look, temperature, and texture rather than the clock.
And one practical note for baked goods: when you scale up significantly, the pan matters as much as the ingredients. Batter that's twice as deep bakes unevenly — the outside overcooks before the center sets. Doubling a recipe usually means moving up a pan size (say, from an 8-inch square to a 9×13) rather than filling the same pan to the brim.
Halving is where this tool earns its keep
Scaling up gets the attention, but scaling down is the more error-prone direction. Halving "1/3 cup" gives you 1/6 cup — a measurement that doesn't exist — and this is exactly where people guess wrong. The scaler converts it to a real answer (about 2 tablespoons plus 2 teaspoons, shown as a friendly fraction of a cup). Small households, test batches, and "I only have half the chicken" situations are the daily use case. The math is the same in both directions; only your confidence changes.