Recipe Scaler
Multiplying is the easy part. A recipe scaler has to give the answer back as something a measuring cup can hold: ⅛ cup is 2 tbsp, and 1½ eggs needs a decision.
Multiplier
- Multiplier 6 servings from a recipe written for 4: 6 / 4.
- 1.5x
- Lines scaled Amounts are rounded to the nearest eighth of a teaspoon and written as the cups and spoons a standard measuring set has.
- 8 of 8
- Part of an egg Whisk the egg so white and yolk are mixed, then use the share the recipe needs by eye or by weighing. Rounding to the nearest whole egg is usually fine in pancakes and batters and less so in custards and cakes, where egg sets the structure.
- beat it, then measure
- Pan for the same depth Keeping the batter or filling at the same depth keeps the cooking close to the original. A round pan's diameter grows by the square root of the multiplier (1.22x), so a 9-inch round becomes about 11 inches; a 9 x 13 becomes about 11 x 15.9. A pan that is too small makes everything deeper and slower to cook through.
- 1.5x the area
- Cooking time Time depends on how thick the food is in the pan and how much is in the oven at once, not on the total quantity. Same depth, similar time; deeper, longer and at risk of over-browning outside before the middle is done. Go by the recipe's doneness test rather than the clock.
- does not scale with the recipe
- Leavening, salt and spice These are scaled in proportion here, which is right for small changes. At large multiples, many bakers and cooks hold back on leavening, salt and strong spices and adjust to taste, because their effect does not grow in a straight line with the batch. Reductions, evaporation and frying oil do not scale linearly either.
- scaled straight
- Metric amounts Cup and spoon measures convert to milliliters exactly (one US cup is 236.6 ml). Grams would need each ingredient's density, which varies with how it is packed. A cup of flour scooped from the bag and a cup spooned in weigh noticeably different amounts, so no gram figure is invented here.
- volume, not weight
| As written | Scaled | Metric |
|---|---|---|
| 1 1/2 cups all-purpose flour | 2¼ cups all-purpose flour | 532 ml |
| 3 1/2 tsp baking powder | 1 tbsp + 2¼ tsp (5¼ tsp) baking powder | 26 ml |
| 1 tbsp sugar | 1½ tbsp sugar | 22 ml |
| 1/4 tsp salt | ⅜ tsp salt | 1.8 ml |
| 1 1/4 cups milk | 1¾ cups + 2 tbsp (1⅞ cups) milk | 444 ml |
| 1 egg | 1½ eggs (beat the last one and use about ½ of it, or round to 1 or 2) | - |
| 3 tbsp butter, melted | 4½ tbsp butter, melted | 67 ml |
| 1 tsp vanilla extract | 1½ tsp vanilla extract | 7.4 ml |
- Ounces are read as weight. Write fl oz for a liquid measure, because the two are different units and only water makes them roughly agree.
- US cups and spoons are assumed: 1 cup = 16 tbsp = 48 tsp. Recipes from elsewhere may use a different cup.
How the Recipe Scaler works
Scaling a recipe is one multiplication per ingredient: the new number of servings divided by the old one, applied to every quantity. Four servings to six is a multiplier of 1.5. Halving is 0.5. The arithmetic is never the hard part.
The hard part is what comes back. A third of a cup times 1.5 is half a cup, which is easy. But three tablespoons times 1.5 is four and a half tablespoons, and a quarter teaspoon times 1.5 is three eighths of a teaspoon, and one egg times 1.5 is one and a half eggs. This scaler rewrites each scaled amount in the cups and spoons a standard measuring set holds, which is the step most scalers skip.
How the measures convert. US kitchen measures are exact multiples of each other: 3 teaspoons to the tablespoon, 16 tablespoons to the cup, so 48 teaspoons to the cup. Two tablespoons is an eighth of a cup, four is a quarter. Every volume amount is worked out in eighths of a teaspoon, then written back as cups (in the quarters and thirds that come in a set), tablespoons and teaspoons. So 0.125 cup comes back as 2 tbsp and 1⅞ cups as 1¾ cups + 2 tbsp. Where the tidy form differs from the plain number in the unit you wrote, both are shown.
Weights are easier than volumes. If the recipe is written in grams, scaling is exact and nothing needs tidying. Ounces and pounds come back as a scale reads them. It is one reason bakers who scale often prefer to work by weight.
What does not scale in a straight line:
- Cooking time. Time follows the thickness of what is in the pan, not the total amount. A doubled cake batter in a pan of double the area cooks in about the original time; the same batter in the original pan is twice as deep and needs longer at a lower temperature, with a real risk of the outside overcooking first. - Pan size. To keep the depth, the pan's area has to change by the multiplier. Area grows with the square of the diameter, so a round pan only needs its diameter multiplied by the square root: a 9-inch pan scaled by 1.5 becomes about 11 inches, not 13.5. - Leavening, salt and strong spices. Scaled in proportion here, which is fine for modest changes. At large multiples many cooks start below the straight-line amount and adjust, because the effect on flavor and rise does not grow in step with the batch. - Evaporation and frying. A doubled sauce in the same pot reduces more slowly, because the surface is the same while the volume doubled. Oil for shallow frying depends on the pan, not on the food.
Eggs come in whole units. When the scaled amount is part of an egg, beat the egg so the white and yolk are mixed and use the share needed, or round to a whole egg. Rounding is usually harmless in batters and pancakes and matters more in custards and cakes, where egg is doing structural work.
Metric amounts for cup and spoon measures are given in milliliters, which is an exact conversion: a US cup is 236.6 ml and a teaspoon 4.93 ml. A cup of flour in grams is a different question. It depends on the ingredient's density and on how it was put in the cup, so this scaler gives volume, not an invented weight.
Recipe Scaler FAQ
How do I scale a recipe?
Divide the number of servings you want by the number the recipe makes, and multiply every ingredient by that figure. A recipe for 4 scaled to 6 has a multiplier of 1.5, so 1 cup becomes 1½ cups and 2 tsp becomes 1 tbsp. Then check the pan size and the cooking time, which do not scale the same way.
How many tablespoons are in a cup?
Sixteen US tablespoons, and three teaspoons to the tablespoon, so 48 teaspoons to the cup. That makes ⅛ cup 2 tablespoons, ¼ cup 4 tablespoons and ⅓ cup 5 tablespoons plus 1 teaspoon.
How do I use half an egg?
Beat one egg until the white and yolk are fully mixed, then use half of it, by eye or by weighing the beaten egg and taking half the weight. In pancakes and most batters, rounding to the nearest whole egg also works; in custards and delicate cakes the exact amount matters more.
Does baking time change when I double a recipe?
It depends on the pan, not the recipe. If the doubled batter goes into a pan with twice the area, the depth stays the same and the time stays close to the original. If it goes into the same pan, it is twice as deep and takes longer, usually at a slightly lower temperature so the outside does not overcook. Use the recipe's doneness test.
Why does the metric column show milliliters instead of grams?
Because cups and spoons measure volume, and milliliters are the exact metric equivalent. Grams depend on what is in the cup and how it was packed, so converting a cup of flour or sugar to grams needs that ingredient's density. Recipes written in grams in the first place scale exactly.