Kitchen math for every recipe, dinner bill, and grocery run.

Multiply every ingredient by the scale factor (target servings ÷ original servings) — but not everything scales linearly. Spices, salt, and leavening intensify in bigger batches: a common rule is to add about 75% of the linear increase past 1× and adjust to taste. Pan size matters too — doubling a batter in the same pan changes depth and bake time, so scale the pan area with the batch.

18–20% of the pre-tax bill is standard for full-service restaurants; 15% reads as adequate, 25% as generous. Counter service commonly runs 0–10%. The tip calculator computes the tip on whatever base you enter and splits the total evenly per person, so an uneven check never becomes a math argument at the table.

Divide each package's price by its size in a common unit — per ounce, per 100 grams, or per item — then compare the results directly. Bigger is usually cheaper per unit, but not always: promotions on small sizes and "bulk premiums" on club packs flip the math surprisingly often. Only a unit-price comparison catches those cases.

Start at 1:16 — one gram of ground coffee per 16 grams (milliliters) of water — which sits in the middle of the Specialty Coffee Association's "golden" range of roughly 1:15 to 1:17. Go toward 1:15 for a stronger cup and 1:17 for a lighter one. Espresso and cold brew use very different ratios, which the coffee calculator handles per brew method.