Why can you eyeball a doubled stew but not a doubled génoise? Because the two activities spend error differently. Cooking is mostly flavor assembly: dissolved seasonings and suspended solids you can taste and correct at nearly any point. Baking is structure chemistry: ratios of flour, water, fat, sugar, egg and leavening lock in an outcome the moment the oven door closes, with no mid-flight corrections. Same multiplication, completely different stakes.
Tolerance budgets, roughly
| Recipe type | Wobble it forgives | Scale freely? |
|---|---|---|
| Soups, stews, braises | ±20% on most lines | yes, both directions |
| Stir-fries, sautés | ±15%, but batch the searing | yes, in batches |
| Cookies, brownies, quick breads | ±10% | yes, ½× to 2× |
| Butter cakes, muffins | ±5–10% | careful past 2× — pan math |
| Sponges, macarons, choux | ±3–5% | scale by grams only |
| Candy, caramel, tempering | volume changes the physics | treat scaling as a new recipe |
These bands are working judgments from practice, not laboratory constants — but they predict failures well. Notice the gradient: the more a recipe depends on foam structure or sugar temperature, the narrower the band.
Baker's percentage: how pros make scaling trivial
Professional formulas sidestep multiplication errors by stating every ingredient as a percentage of the flour weight, flour being 100% by definition. A classic rustic loaf:
| Ingredient | Baker's % | At 500 g flour | At 2 kg flour |
|---|---|---|---|
| Bread flour | 100% | 500 g | 2000 g |
| Water | 70% | 350 g | 1400 g |
| Salt | 2% | 10 g | 40 g |
| Instant yeast | 1% | 5 g | 20 g |
Any batch size is now one multiplication per line with the ratios self-auditing — if salt isn't near 2%, you typo'd. You don't need to adopt the full system to borrow its lesson: convert a baking recipe to grams once, and every future scale of it becomes arithmetic you can check.
The recipes that aren't really scalable
- Candy and caramel — sugar syrup stages are read by thermometer depth and evaporation rate; both change with volume. Small batches especially can overshoot stages in seconds.
- Emulsified sauces (mayonnaise, hollandaise) — scale up fine, but halving below one egg yolk's worth leaves too little emulsifier to hold.
- Pressure-cooker recipes — minimum liquid requirements are about the machine, not the food; never scale the liquid below the manufacturer's floor.
- Anything sized to one egg — see how to halve an egg before halving further.
Skip the long division. Paste your ingredient list into the scaling pot and get every line converted at once.
Open the calculator