Calculation methods

Coffee-to-water ratio

Input water = dry coffee × ratio denominator. Dry coffee = input water ÷ denominator. A ratio of 1:16 means 16 g input water per 1 g dry coffee. Grams measure mass. For ordinary brewing water, 1 mL ≈ 1 g is only a convenient approximation; a scale avoids density assumptions.

At 1:16, 20 g of dry coffee calls for 320 g of input water. Starting with 300 g of water at the same ratio calls for 18.75 g of coffee. The collected drink will usually weigh less than the input water.

Batch brew planner

Total input water = portions × input water per portion, or the directly entered total. Dry coffee = total input water ÷ denominator. Each pour = total × stage percentage ÷ 100. Stage percentages must total 100%; cumulative readings show what the scale should read, assuming it is not reset between pours.

Three portions of 200 g of brewing water give 600 g input water. At 1:16, use 37.5 g of coffee. A 15% / 35% / 50% plan adds 90 g, 210 g and 300 g, with scale readings of 90 g, 300 g and 600 g.

Espresso ratio

Beverage ratio = mass of espresso collected in the cup ÷ dry coffee dose. Yield = dose × denominator; dose = yield ÷ denominator. Espresso yield is the liquid beverage leaving the machine, not water put into the tank. Shot time is recorded independently.

An 18 g dry dose and 36 g beverage yield give 1:2. A recorded 28-second shot is a note about that shot; the calculator does not predict time, grind setting or taste.

Coffee dilution

Dissolved coffee solids = starting coffee mass × starting TDS ÷ 100. Final mass = starting mass × starting TDS ÷ target TDS. Added water = final mass − starting mass. This is a mass balance assuming complete mixing, no losses, and added water with negligible coffee solids.

A 250 g coffee at measured 1.8% TDS contains 4.5 g of dissolved coffee solids. To reach 1.35%, the final mass is 333.33 g: add 83.33 g water, assuming the added water contributes negligible coffee solids.

Coffee and water are different measurements

Filter recipes use dry grounds and input brewing water. Espresso recipes use dry grounds and collected beverage. Those ratios describe different stages of brewing.

Pour stages and scale readings

The batch planner accepts two to six stages, including zero-percent stages, and requires their sum to be 100%. Added water is the amount in that stage; cumulative water is the total reading on an initially tared scale. No timings or automatic brewing instructions are inferred.

Measured strength and dilution

TDS is expressed as a percent by mass. The calculator conserves dissolved coffee solids and uses measured coffee mass, not an assumed density or cup volume. A target above the starting TDS cannot be reached by adding water. Equal concentrations require zero added water. A target of zero has no finite solution.

Limits and precision

Positive masses are limited to 1,000,000 g; direct batch water to 10,000,000 g, whole portions to 10,000, ratio denominators to 1,000 and shot time to 0–3,600 seconds. TDS must be greater than 0 and at most 100%. Results display up to two decimals but use unrounded values internally. These are mathematical planning tools, not equipment or sensory measurements.