Calculator methodology

All of CoffeeHQ's calculators and tools share the same underlying conventions, described here once rather than repeated on every tool page. Method-specific details (like the caffeine estimator's model) have their own dedicated page.

Units

Internally, every calculator converts mass to grams and volume to millilitres before doing any math, then converts back for display. Coffee-to-water ratios follow the "1 part coffee to N parts water" convention throughout (e.g. a ratio of 16 means 1g of coffee per 16g of water) — this is a CoffeeHQ-wide convention, not a universal industry standard. "Cup" is defined as 240ml and "shot" as 30ml wherever they appear; these are stated explicitly rather than assumed, since both vary by country and by kitchen. Tablespoon and teaspoon measures are deliberately not used for coffee mass, since a tablespoon of ground coffee varies enormously with grind size and bean density.

Ranges over false precision

Where a result is genuinely uncertain (caffeine content, cost estimates based on assumptions), the calculator shows a range or explicitly labels the figure as an estimate rather than presenting a single confident-looking number. Where a result follows directly and exactly from your inputs (a scaled recipe, a ratio-derived dose), it is shown as an exact figure, because it is one — deterministic arithmetic on the numbers you gave.

Recipe scaling

Scaling a recipe up or down (the brew recipe scaler, batch brew calculator) multiplies dose, water and milk linearly by the change in servings. This is a deliberate simplification: real brewing does not always scale perfectly linearly, since extraction dynamics shift with bed depth and brewer geometry at very different batch sizes. Where a scaled water volume falls outside a brewer's stated capacity, the tool flags it rather than silently returning a number the brewer can't actually hold.

Currency

The cost-per-cup calculator defaults to GBP, formatted via standard locale-aware currency formatting. Other currencies are not currently supported but the underlying calculation is currency-agnostic and locale flexibility is preserved for future expansion.

Unit consolidation

Where a tool combines ingredient quantities from more than one source (the shopping list generated from multiple drinks), quantities are merged strictly by ingredient identity — never by matching similar-sounding names — and only when they share the same unit. Quantities in different units for the same ingredient are kept as separate line items rather than guessed at with an assumed conversion.

No external AI

Every calculator, the coffee-maker selector, the troubleshooting engine and the drink finder run on fixed, explicit, deterministic rules over your inputs and CoffeeHQ's own published data. None of them call an external AI or machine-learning model, and none of them fabricate a result they don't have the data to support.