Brew Calculator
Design a brew on paper. Set the variables and see the theoretical water, beverage, extraction yield and strength, plotted on the brewing control chart. Then brew it, measure it, and compare.
- Cup will taste intense for this method. Use a wider (higher) ratio or dilute after brewing (bypass).
Enter a measured brew (refractometer)
The prediction is a simplified model: base yield per method, adjusted for grind (surface area), temperature, contact time (diminishing returns) and ratio, with TDS from mass balance. Read Extraction, TDS and the Brewing Control Chart for the theory.
TransparencyHow the calculator computes these numbersshow
1. Definitions and mass balance (exact)
water = dose × ratio (g) beverage = water − dose × retention (g) retention = water held by spent grounds, g per g coffee dissolved = EY / 100 × dose (g) TDS = dissolved / beverage × 100 (%) measured EY = TDS × beverage / dose (%) what you compute from a refractometer reading
These are definitions, not models. Retention per method is a CoffeeLab parameter (pour over 2.1, French press 2.4, AeroPress 2, espresso 1.1, cold brew 2.6, moka 1.6 g/g), chosen from typical practitioner measurements; weigh your beverage if you want the exact number for your brewer.
2. Standards (cited)
The ideal box on the chart is 18–22 % extraction yield by the method's strength window (filter 1.15–1.45 % TDS, espresso 8–12 %), following the SCA Golden Cup standard, itself descended from Lockhart's 1957 brewing control chart. Modern light roasts on good grinders are often brewed happily above 22 %, so the box is a compass, not a fence.
3. The prediction model (CoffeeLab working assumptions)
EY = base(method) + 0.9 × (baseGrind − grind) each step finer adds ~0.9 % EY (more surface area, slower flow) + 0.15 × (T − T_default) per °C, hot methods only + 1.4 × log2(time / time_default) doubling contact time adds ~1.4 % EY (diminishing returns) + 0.8 × log2(ratio / ratio_default) more water per gram keeps the concentration gradient steeper clamped to 8–30 %
The directions of these effects are well established: extraction rises with surface area and contact time and follows diffusion kinetics (multiscale extraction modelling, 2015; espresso modelling, 2020). The coefficients are not fitted to a dataset. They were chosen to reproduce the rough size of effects reported in that literature and in practitioner measurements, and they are deliberately linear so you can see each lever's contribution. Treat the direction and the order of magnitude as reliable and the second decimal as illustrative. Note also that a 2020 UC Davis study found brew temperature, once strength and extraction are held fixed, has little sensory effect, so temperature matters here mainly through the extraction it produces.
Caffeine is estimated as 1.2 % of dose (typical arabica) scaled gently with extraction, since caffeine dissolves early. Per-method bases: Pour Over 20 % at grind 6, 94 °C, 180 s, 1:16.7; French Press 19 % at grind 8, 93 °C, 240 s, 1:15; AeroPress 19.5 % at grind 5, 88 °C, 120 s, 1:13; Espresso 20 % at grind 1.5, 93 °C, 28 s, 1:2; Cold Brew 18 % at grind 9, 20 °C, 16 h, 1:8; Moka Pot 19 % at grind 3, 96 °C, 150 s, 1:7.
4. Calibrate it to your setup
Brew, measure TDS with a refractometer, enter it below the chart, and log the brew. As logged measurements accumulate, the gap between predicted and measured extraction tells you how your grinder and water differ from the model's assumptions. The plan is to fit these coefficients per grinder once there is enough data (see the analytics page for what has been logged so far).
Sources
- SCA Coffee Standards: Golden Cup Standard (brewed coffee strength and extraction) — Specialty Coffee Association, Specialty Coffee Association, 2018. Tier 1. Checked 2026-09-05.
- The Soluble Solids in Beverage Coffee as an Index to Cup Quality — Ernest E. Lockhart, Coffee Brewing Institute (publication), 1957. Tier 2. Checked 2026-09-05.
- Modelling of coffee extraction during brewing using multiscale methods: An experimentally validated model — Kevin M. Moroney, William T. Lee, Stephen B. G. O'Brien, Freek Suijver, Johan Marra, Chemical Engineering Science, 137, 216-234, 2015-12-01. Tier 1. Checked 2026-09-05.
- Brew temperature, at fixed brew strength and extraction, has little impact on the sensory profile of drip brew coffee — Mackenzie E. Batali, William D. Ristenpart, Jean-Xavier Guinard, Scientific Reports, 10, 16450, 2020-10-05. Tier 1. Checked 2026-09-05.
- Systematically Improving Espresso: Insights from Mathematical Modeling and Experiment — Michael I. Cameron, Dechen Morisco, Daniel Hofstetter, et al. (senior author Christopher H. Hendon), Matter, 2(3), 631-648, 2020-01-22. Tier 1. Checked 2026-09-05.
Model code: lib/coffee.ts. Information collected 2026-09-05; last reviewed 2026-09-05. Trust tiers per the wiki's sourcing policy.