How to scale recipe quantities: from four portions to three
Multiply measured quantities by ¾ to turn four equal-size portions into three. Check an original worked list, try a short exercise and keep cooking instructions separate from the arithmetic.
One factor for the ingredient list
A recipe makes four portions and you want three of the same size. Multiply each measured ingredient quantity by 3 ÷ 4 = 0.75, or ¾. Write the new list before you start, so you do not switch between the original and adjusted amounts halfway through.
This is a way to plan quantities. The calculation does not establish cooking time, oven temperature or whether a changed recipe will work. Start with a recipe you trust and read its preparation instructions as well as its ingredient list.
1. Check what the portions mean
The portion-count method assumes that the new portions are the same size as the original ones. Three larger portions are a different target. Check the recipe’s stated yield first: four portions, four small jars or four trays are not interchangeable.
For equal-size portions, the rule is: factor = portions wanted ÷ original portions. New ingredient quantity = original quantity × factor. BCcampus’s culinary training text describes this method. Going from four to three gives a factor below 1; going from four to six gives 1.5.
2. Work through a four-to-three example
These rows are an invented ingredient list for arithmetic practice. They are not a tested recipe or preparation instructions. Keep each ingredient’s condition and unit: dry pasta stays dry pasta, and millilitres stay millilitres.
Worked ingredient list
For 4 portions × ¾ For 3 portions
Dry pasta: 280 g × ¾ 210 g
Chopped tomatoes: 400 g × ¾ 300 g
Grated cheese: 60 g × ¾ 45 g
Olive oil: 20 ml × ¾ 15 ml
Dried herbs: 1 tsp × ¾ ¾ tspEvery row uses the same factor. Here “tsp” means the same measuring teaspoon in both columns.
Check one row without a calculator
One quarter of 280 g is 70 g. Three quarters are 3 × 70 g = 210 g. Or remove one quarter: 280 g − 70 g = 210 g. Both checks agree.
Keep units attached to the numbers. Multiplying 20 ml by ¾ gives 15 ml, not 15 g. This calculation does not convert a volume into a weight. If a recipe gives several units for one quantity, first express that quantity in one consistent unit.
3. Keep the exact result before rounding
If a line starts at 50 g, its new amount is exactly 37.5 g. If you choose to measure to the nearest gram, write “approximately 38 g” beside that exact result. The rounding adds 0.5 g; do not hide it by writing an equals sign. Whether that adjustment is acceptable depends on the ingredient and recipe.
Keep fractions through the calculation when convenient. For a six-to-four change, the factor is ⅔. Then 240 g × ⅔ = 160 g exactly. Rounding the factor first to 0.67 would give 160.8 g. Round the final measurement only when you have decided how to measure it.
A fractional whole ingredient needs a plan too. If the answer is 1½ eggs, rounding it to two changes the proportions. A recipe already written for your desired yield may be more practical. Leave “to taste” as a note; it has no starting number to multiply.
4. Keep the cooking instructions beside the list
Do not multiply the oven temperature or cooking time by ¾. For example, a 40-minute instruction does not become a reliable 30-minute instruction just because you need three quarters of the ingredients.
Nebraska Extension notes that a smaller batch may need a smaller pan and may bake for less time. Colorado State University Extension also identifies time, temperature, pan size and seasoning as details that may need adjustment. The ingredient factor does not calculate those adjustments. Check the recipe’s own guidance for the new batch and equipment.
This worksheet is not a method for adapting canning or other preservation recipes.
Your turn: six portions become four
A second arithmetic-only list has 300 g of one ingredient, 90 ml of another and ¾ teaspoon of a third. Keep portion sizes unchanged. Find the factor and all three new quantities before reading the answer.
Answer
The factor is 4 ÷ 6 = ⅔. The quantities become 200 g, 60 ml and ½ teaspoon. The last line is ¾ × ⅔ = 6/12 = ½. Every measured amount is smaller, while each unit stays the same.
Copy this quantity worksheet
Recipe and source:
Original portions:
Portions wanted (same size):
Factor = wanted ÷ original:
Ingredient and condition:
Original amount + unit:
Exact result (original × factor):
Amount I can measure:
Any rounding or unresolved question:
Repeat the ingredient lines as needed.
Recipe guidance for this batch and pan:
Cooking instructions checked separately:Keep the original recipe with your new list. Resolve awkward measurements before preparing the food.