Methodology & data sources

Cups to grams — ingredient densities

A cup is a measure of volume, so converting it to grams needs a density for each ingredient. Our default is the King Arthur Baking ingredient weight chart — the reference most US test kitchens treat as standard. Flours assume the spoon-and-level method (all-purpose flour = 120 g per cup); brown sugar is measured packed, as recipes intend. Volume math uses the US legal cup of 236.588 ml. Volume↔volume and weight↔weight conversions are ingredient-independent; only volume↔weight uses the density.

Where we deliberately differ. King Arthur lists every liquid at 227 g per cup, which comes from reading 8 fluid ounces as 8 weight ounces. That is convenient but physically wrong — a cup of water weighs about 237 g, and whole milk, being denser than water, about 240 g. For nine ingredients where the chart's shortcut would put us further from what your scale reads, we use the measured density instead and say so. Each of those values carries a written reason in the source data, and a test asserts that every other value matches the chart exactly, so nothing can drift from its source unnoticed.

Cake pan converter — capacities & batter depth

Pan capacities come from published manufacturer and test-kitchen measurements (King Arthur Baking and Wilton pan charts), with custom sizes falling back to geometric volume (1 US cup = 14.4375 cubic inches). The ingredient multiplier is the ratio of the two pans' capacities — a volume comparison, not a flat area one, which is why a deeper pan isn't treated the same as a wider one. Time and temperature guidance is driven by batter depth (volume ÷ area) assuming the standard two-thirds fill: deeper batter bakes longer at a lower temperature, shallower bakes faster. Always confirm with a toothpick.

Recipe scaler — fractions & safe limits

The scaler multiplies each ingredient by your factor and rewrites the result in fractions you can actually measure (it understands mixed numbers like "2 1/2", unicode fractions like "¾", and decimals). Lines with no quantity ("pinch of salt") pass through untouched, and fractional eggs are flagged with a practical fix. It warns beyond about 3× because leavening, salt, and strong spices don't scale linearly — professional bakers scale those to roughly three-quarters of the math and adjust to taste.

Oven temperature converter

Fahrenheit↔Celsius use the exact formulas (°C = (°F − 32) × 5/9). Gas marks follow the standard UK gas-mark table (gas mark 4 = 350 °F / 180 °C, "moderate"), and the fan/convection column applies the conventional −20 °C reduction (≈ 25–30 °F), since circulating air transfers heat faster than still air.

What these tools deliberately don't cover

CrumbCalc does one thing: the measurement and proportion maths of baking — weights, volumes, pan capacities, ratios, and temperature scale conversions. Being clear about the edges of that matters as much as the figures inside it, so:

• We publish no food-safety thresholds. Nothing here tells you a safe internal temperature for meat, poultry, eggs or leftovers. For those, use FoodSafety.gov's safe minimum temperature charts — a government source that is maintained, which a baking calculator should not pretend to be. Where a tool mentions an internal temperature it is a doneness cue for a bake (a cake is set around 200–210 °F), never a safety threshold.
• We publish no canning or preserving guidance. Home canning is the one kitchen task where getting a number wrong can be genuinely dangerous rather than merely disappointing, and its processing times depend on jar size, acidity and altitude together. Our high-altitude pages deliberately stop at baking and stove-top work; for preserving, follow the National Center for Home Food Preservation.
• Our numbers can't harm your oven. Everything we publish sits inside the normal baking range (225–475 °F / 110–245 °C), well below the temperatures an oven reaches during its own self-clean cycle, and every oven has its own thermostat and thermal cut-outs. A conversion that's off by a few degrees costs you a disappointing bake, not a damaged appliance. We give no electrical, appliance-repair or equipment-modification advice of any kind.
• Estimative tools say so on the page. Where no authoritative published figure exists — frosting quantities, for instance — we compute from a stated model with its assumptions visible, rather than copying an unsourced chart or inventing a citation.

One honest caveat that outweighs all our rounding: your oven is probably the least accurate instrument in this chain. Home ovens commonly run 25 °F hot or cold and swing further as the thermostat cycles. Published gas-mark charts also disagree with each other by 5–10 °C, because gas marks are defined in Fahrenheit (gas 1 = 275 °F, then +25 °F per mark) and every publisher rounds the Celsius column differently — ours stays within 5 °C of the exact conversion, and a test enforces it. An oven thermometer settles all of it for the price of a coffee.

How we keep it accurate

The figures these tools rely on are pinned by an automated suite of over 180 checks that runs before anything ships. Every one of the ingredient densities is asserted against the King Arthur chart value, and the nine that deliberately differ must carry a written reason — a value cannot quietly drift from its source, and a departure cannot go undocumented. Beyond straight transcription, the checks test the derivations: that Wilton's wedding counts really are the cake's area divided by a 1 × 2 in slice, that a party slice never feeds more people than a smaller wedding slice, that pan geometry stays within a fifth of published capacity, and that a cup of water weighs what physics says it does. Testing the rule rather than re-stating the number is what catches a typo; simply asserting the values we shipped would not.

Between you and that reference there is no server and no AI guessing a number — the engine runs entirely in your browser, so what you see is the arithmetic on the cited data, nothing more. Spot a figure that looks off? Tell us and we'll check it against the reference and correct it.