How to scale a batch recipe without breaking it
Multiplying every line by the same factor is the easy part. Seasoning, equipment and yield are what actually break, and yield is what changes your cost.
Multiply every ingredient by the scaling factor, then check the four things that do not follow it: seasoning, leavening, equipment capacity, and cook time. The arithmetic is trivial and is not where scaled batches go wrong.
Scaling factor = portions you want divided by portions the recipe makes
Worked example: chili for 40
The chili batch makes 12 portions and costs $31.00. You need 40 portions for an event.
Scaling factor = 40 divided by 12 = 3.33
- Ground beef: 2 kg becomes 6.67 kg
- Kidney beans: 1.2 kg becomes 4 kg
- Batch cost: $31.00 becomes $103.33
Cost per portion = $103.33 divided by 40 = $2.58, exactly what it was at 12
That is the reassuring half. Cost per portion is scale-invariant: multiply the inputs and the portions by the same number and the ratio between them cannot move.
Yield is not scale-invariant, and that is what changes your cost
A bigger pot has less surface area for its volume, so a scaled sauce reduces more slowly over the same time. Cook it to the clock and you finish with more liquid and a weaker product. Cook it to the texture and it takes longer than three times as long.
Either way the finished output is no longer 3.33 times the original, and cost per portion moves with it. If the chili that yielded 12 portions yields 38 at the larger scale rather than 40:
Cost per portion = $103.33 divided by 38 = $2.72, a 5.3% increase nothing in the recipe explains
Weigh the finished batch at the new scale and store that yield against the scaled recipe. Do not assume the yield scaled.
The four things that do not scale linearly
- Salt, chile, and garlic. Strong seasonings intensify faster than volume grows. Start at about 75% of the multiplied amount and correct to taste, which is cheaper than the alternative.
- Leavening. Baking soda and baking powder behave the same way, and an over-leavened large batch collapses rather than tasting slightly off.
- Equipment. A 6 quart pot does not hold 3.33 times a 6 quart recipe. Splitting into two batches is a real answer, but two batches cooked side by side are not one batch, and their yields differ.
- Time. Cook time tracks depth and surface area, not volume. A tray twice as deep takes much more than twice as long, and the outside overcooks while it waits.
Scaling down has the opposite failure
Halving a recipe that calls for one egg, or a quarter teaspoon of something, forces a rounding decision that a large batch never faces. Round in the direction that is recoverable: you can add more salt, and you cannot take it out.
Frequently asked questions
- Does scaling change my cost per portion?
- Not by itself. The arithmetic is a pure ratio, so it cancels out. It changes in practice only when the finished yield does not scale in proportion, which is common on anything that reduces, bakes, or is portioned by hand.
- Can I scale a bread or pastry recipe the same way?
- Scale it by weight, not by volume or by count, and work in baker's percentages if you have them. A recipe written in cups does not survive being multiplied, because the error in each measurement multiplies with it.
- How far can I scale before I should re-test?
- Roughly double is usually safe on a stable recipe. Past that, run it once and weigh the result before you sell it, because you are testing your equipment as much as your recipe.
- Should I re-cost the recipe after scaling?
- Re-cost it if the yield moved. If the batch produced fewer portions than the factor predicted, the stored cost per portion is understated for every dish that draws on it.
Multiply the quantities in seconds, then weigh the finished batch and re-cost it.
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