Recipe Scaler: Double, Halve or Resize a Recipe

How recipe scaling works

Scaling a recipe takes one division and one multiplication. Divide the servings you want by the servings the recipe makes. That gives your scale factor. Next, multiply each item by that factor. Going from 4 servings to 6 gives 6 ÷ 4 = 1.5× (150%). Halving from 8 to 4 gives 4 ÷ 8 = 0.5× (50%). Doubling from 4 to 8 gives 2× (200%). If you already know the batch ratio, pick Batch multiplier in the first box.

Two metric rules show up in U.S. kitchens and on food boxes. In NIST SP 811 (Appendix B.8) and NIST Handbook 44 (Appendix C), 1 U.S. gallon is 231 cubic inches (3,785.411784 mL). That makes 1 U.S. cup (8 fl oz) equal to 236.588 mL. One fluid ounce is 29.574 mL, 1 tablespoon is 14.787 mL, and 1 teaspoon is 4.929 mL. Food labels use simpler numbers. In 21 CFR 101.9(b)(5)(viii), the FDA rule states: "For nutrition labeling purposes, a teaspoon means 5 milliliters (mL), a tablespoon means 15 mL, a cup means 240 mL, 1 fl oz means 30 mL, and 1 oz in weight means 28 g." NIST's Metric Kitchen guide lists the same 5 mL, 15 mL, 30 mL, 240 mL, and 28 g values and notes: "These approximate equivalents of common capacity (volume) and mass measurement units may be used for home cooking applications."

Fractions and spoon steps make scaled recipes easy to scoop with standard nested cups. The table above turns each scaled volume into eighth- and third-cup fractions plus cup-and-spoon steps. In the default 1.5× batch, 2 cups becomes 3 cups and 1 1/2 cups becomes 2 1/4 cups. Then 3/4 tsp becomes 1 1/8 tsp, and 3 tbsp becomes 4 1/2 tbsp, which steps up to 1/4 cup + 1 1/2 tsp.

Recipe scaling formulas

scale factor = desired servings ÷ original servings
scaled amount = original amount × scale factor
desired servings (in multiplier mode) = original servings × batch multiplier
1 cup = 16 tbsp = 48 tsp = 8 fl oz = 236.588 mL (NIST) = 240 mL (21 CFR 101.9)
1 tbsp = 3 tsp = 0.5 fl oz = 14.787 mL (NIST) = 15 mL (21 CFR 101.9)
1 tsp = 1/3 tbsp = 4.929 mL (NIST) = 5 mL (21 CFR 101.9)
1 lb = 16 oz = 453.59237 g (NIST exact); 1 oz = 28.350 g (NIST) = 28 g (21 CFR 101.9)

Worked recipe scaling examples

Default home recipe (4 servings to 6 servings, 1.5×). Dividing 6 desired servings by 4 original servings gives a 1.5× factor (150%). Ingredient 1 (2 cups flour) becomes 2 × 1.5 = 3 cups (709.8 mL NIST / 720 mL FDA). Ingredient 2 (1.5 cups milk) becomes 1.5 × 1.5 = 2.25 cups, or 2 1/4 cups (532.3 mL NIST / 540 mL FDA). Ingredient 3 (0.75 tsp salt) becomes 0.75 × 1.5 = 1.125 tsp, or 1 1/8 tsp (1.13 tsp on the card, 5.5 mL NIST / 5.6 mL FDA). Ingredient 4 (3 tbsp butter) becomes 3 × 1.5 = 4.5 tbsp, which is 13.5 tsp and steps up to 1/4 cup + 1 1/2 tsp (66.5 mL NIST / 67.5 mL FDA).

King Arthur Baking French bread formula (0.9× multiplier). King Arthur Baking shows a French bread formula that totals 201.9 pounds at 168.25% total baker's percentage. It uses 120 lb flour (100%), 78 lb water (65%), 2.4 lb salt (2%), and 1.5 lb yeast (1.25%). To scale the batch down to 150 pounds of dough, divide 150 by 168.25 to get a factor of 0.8915. As King Arthur explains, "It is preferable to round this figure up, because it is better to have a little extra bread rather than not enough, so we round up to 0.9." Entering 0.9× with the percentage weights (100 lb flour, 65 lb water, 2 lb salt, 1.25 lb yeast) gives 90 lb flour and 58.5 lb (58 lb 8 oz) water. Salt becomes 1.8 lb (1 lb 12.8 oz exact, shown as 1 lb ≈ 12 3/4 oz) and yeast becomes 1.125 lb (1 lb 2 oz, or 1.13 lb on the card), for 151.43 pounds in all.

USDA school oatmeal batch (Food Buying Guide example). Suppose you need 70 one-cup servings of cooked oatmeal. The USDA table lists 1/2-cup servings at 23.40 servings per pound of dry instant rolled oats. First divide 1.0 cup by 0.5 cup to get a serving factor of 2. Multiply 2 by 70 to get 140 half-cup servings. Dividing 140 by 23.40 servings per pound gives 5.98 pounds of dry oats, which rounds up to 6 pounds.

Assumptions and kitchen limits

• Every item is multiplied by the same scale factor: desired servings ÷ original servings, or the batch multiplier.
• Card values round half up to two decimals (1.125 shows as 1.13). A rounded decimal for a third (0.33 or 0.67) counts as exactly 1/3 or 2/3. Kitchen fractions and spoon steps use the exact ratio before snapping to the nearest kitchen fraction (eighths, plus 1/3 and 2/3).
• When an amount lands halfway between two kitchen fractions (such as 3/16 = 0.1875 between 1/8 and 1/4), it rounds up to the next size. 21 CFR 101.9(b)(5)(ix) rounds a label serving size up in the same way.
• Volume step-ups use exact U.S. liquid ratios: 1 cup = 16 tbsp = 48 tsp, 1 fl oz = 2 tbsp = 6 tsp, 1 pt = 2 cups, 1 qt = 4 cups, and 1 gal = 16 cups. Weight step-ups use 1 lb = 16 oz.
• NIST metric values use Handbook 44 factors (4.929 mL per tsp and 28.350 g per oz). FDA label values use 21 CFR 101.9(b)(5)(viii) household rules (5 mL per tsp, 15 mL per tbsp, 30 mL per fl oz, and 28 g per oz).
• Every row is scaled in a straight line. Salt, spices, yeast, baking powder, eggs, pan size, bake time, oven heat, and high-altitude cuts are not adjusted. The notes on kitchen adjustments say what to watch; they are not tested guidance.

How to measure and bake a scaled batch

Weigh dry flour, sugar, and butter in grams when scaling past 1.5×. In the default 1.5× batch, use the NIST metric column (709.8 mL for 3 cups, 532.3 mL for 2 1/4 cups) for liquids. Convert dry cups to grams with the cups to grams converter so scoop error does not grow.

Use the cup-plus-spoon step for odd tablespoon counts. Instead of counting 4 1/2 tbsp of melted butter in the default 1.5× batch, scoop once with a 1/4-cup measure (4 tbsp) plus 1 1/2 tsp, or check single-unit swaps in the kitchen measurement converter.

Match pan area to the scale factor to keep batter depth about even. A 1.5× cake batch fits 1.5 times the pan area. One move is from an 8 × 8-inch pan (64 sq in) to a 9 × 11-inch pan (99 sq in). Bake time may change, so check early. Compare pans in the baking pan size converter.

Weigh beaten egg when a scaled recipe asks for a fraction of an egg. Beat one egg, weigh it, and use half that weight for 0.5 egg. Check egg size swaps in the egg size converter.

Recipe scaling questions