A scaling calculator is only as honest as the standards underneath it. This page is the complete specification of ours — the unit definitions, the density table policy, the rounding rules, and the test cases the engine must pass before any change ships. If a number on this site ever disagrees with this page, this page wins and the bug is ours to fix.
Unit standard
- 1 US cup = 240 ml (US legal cup) · 1 tablespoon = 15 ml · 1 teaspoon = 5 ml · 1 fl oz = 30 ml.
- Weight: 1 oz = 28.35 g · 1 lb = 453.6 g.
- Butter: 1 stick = ½ cup = 8 tbsp = 113 g.
- Eggs: US large = 50 g without shell (white 30 g, yolk 18 g); medium = 44 g.
How quantities are computed
The engine parses each line into quantity, unit and ingredient, then multiplies the quantity as an exact fraction — ⅓ stays 1/3, never 0.3333. Floating-point arithmetic appears only at the final display step. Ranges ("1–2 tsp") scale both ends. Lines without a quantity ("salt to taste") pass through unchanged.
Rounding and display rules
- Results snap to measures that exist in a drawer: teaspoon fractions down to ⅛ (and thirds, for the ⅓-cup family), half-tablespoons, and the standard cup fractions ¼ ⅓ ½ ⅔ ¾.
- Amounts that don't land on a single measure are re-expressed as combinations — ⅜ cup becomes ¼ cup + 2 tbsp — preferring fewer scoops and whole tablespoons.
- A snap is accepted only within 2.5% of the exact value (2% for spoon amounts); otherwise the combination form is used instead.
- Below roughly ⅛ teaspoon the display says "a pinch" rather than pretending ¹⁄₃₂ tsp is measurable.
- Gram weights round to 0.5 g under 10 g, 1 g under 100 g, and 5 g above that.
The density table
Cup-to-gram values cover ~30 staples, assume spoon-and-level technique for flours and powders, packed brown sugar, and round to the nearest 5 g per cup. They are reference values for home cooking: technique alone moves flour ±10–20%, which is why the table refuses false precision. The complete table is published in the cups-to-grams guide and embedded in the calculator's source, where anyone can audit it.
Advisory notes, and their limits
When a scaled list contains eggs, salty condiments, hot spices, leavening, yeast, setting agents or reducible alcohol, the calculator attaches a short note (the reasoning lives in the nonlinear ingredients guide). These notes are deliberately conservative starting points — "begin at 75% and taste" — not promises about your stove, your pan or your palate. Cooking judgment stays yours.
The test cases every change must pass
| Input line | Factor | Required output |
|---|---|---|
| 2 cups all-purpose flour | ×½ | 1 cup · ≈120 g |
| ¾ cup granulated sugar | ×½ | ¼ cup + 2 tbsp · ≈75 g |
| 1½ tbsp olive oil | ×2 | 3 tbsp |
| 3 large eggs | ×½ | 1½ eggs · ≈75 g + weighing note |
| 1 tsp baking soda | ×3 | 1 tbsp + leavening note |
| ⅓ cup honey | ×1½ | ½ cup · ≈170 g |
| 1–2 tsp chili flakes | ×2 | 2–4 tsp + heat note |
| Pinch of salt | ×2 | 2 pinches |
| 250 g butter | ×¾ | 190 g |
| 1 cup milk | ×1½ | 1½ cups · ≈360 g |
What this site does not do
- No nutrition, dietary or medical guidance — we scale quantities, nothing else.
- No bake-time prediction — time follows pan geometry, and we'd rather teach the rule than fake a number.
- No scraped recipe content — every chart and guide is researched and written for this site, and corrections are welcome at contact.