A recipe scaler multiplies every ingredient up or down to feed more or fewer people. The Toolenza calculator handles the arithmetic; the judgment calls — pan size, cook time, seasoning — are still on you.

What scales linearly

• Most ingredients by weight or volume. Doubling a soup is fine; tripling a stew is fine. Multiply and move on.
• Most baking ratios — flour, sugar, fat, dairy. The structural ingredients scale exactly.

What doesn't scale linearly

• Pan size and bake time. A doubled cake recipe in a single-sized pan overflows. Either use two pans or a larger one. A larger / deeper pan needs more time at a lower temperature — typically 25 °F lower and 15–25% longer.
• Salt and seasonings. Salt scales roughly 0.75× rather than 1× when doubling because the dish's total surface area to volume ratio drops — less evaporation, less concentration loss. Start with 0.75× and adjust to taste.
• Leavening (baking powder, baking soda, yeast) — scales sub-linearly. A doubled cake batter often needs 1.5× leavening, not 2×, because the larger batter has less surface to bubble through.
• Acidic ingredients in marinades — scale carefully; too much vinegar or lemon in a doubled marinade can "cook" the protein.
• Spirits and extracts — scale at 0.75× of linear. Vanilla and alcohol intensify in larger volumes.

Worked example — scaling from 4 servings to 12

A chicken recipe for 4 calling for 1 tsp salt, 1 tbsp olive oil, 1 lemon's juice:

• Tripled volume of meat, water, vegetables, oil — straight 3× linear.
• Salt: 1 tsp × 0.75 × 3 ≈ 2.25 tsp, not 3 tsp. Adjust to taste at the end.
• Lemon juice: same caution. Start at 2.25× linear; add more if needed.
• Cook time: 25–35% longer. The thermometer is the authority, not the timer.

Pitfall

Scaling down is harder than scaling up. Halving a recipe with one egg is awkward — most pros switch to a weight-based formula (50 g egg = ~1 large egg). Scaling down baking recipes below 50% rarely works; the pan + time relationship breaks down.