What CupTune calculates
Brew water = dry coffee × water ratio. Espresso beverage = dose × beverage ratio. Approximate filter yield = water − dose × the visible absorption coefficient.
Extraction yield = beverage mass × (measured TDS ÷ 100) ÷ dry dose × 100. Dilution preserves dissolved solids: final mass = concentrate × current TDS ÷ target TDS.
The timer derives elapsed time from an absolute anchor. It never assumes interval callbacks ran while the tab was backgrounded.
What the measurements do not establish
- TDS is never inferred from colour, method or taste.
- Absorption and cold-brew retention are editable approximations.
- Taste descriptors do not prove a single extraction cause.
- Recipe times do not override taste, flow, equipment limits or food safety.
How to use the result
Use a scale, record the actual beverage and change one controllable variable. SCA explains brew ratio and espresso beverage ratio; its current Brewing Chart research describes the measured TDS, extraction-yield and brew-ratio relationship. The formulas here apply those definitions and mass balance. Authored recipes and sensory suggestions remain starting preferences, not standards or diagnoses.