Cold Brew Concentrate

Coffee Needed is calculated purely from Concentrate Volume divided by (the coffee-to-water ratio that Strength selects, plus one) -- 9 for Regular's 1:8, 6 for Strong's 1:5, or 5 for Concentrate's 1:4 -- since a "1:8" ratio means 1 part coffee to 8 parts water, or 9 parts total. It describes how much coffee goes into brewing the concentrate itself. Serving Dilution Ratio only affects how that finished concentrate is diluted at serving time, which is a separate step that happens after brewing, so it has no effect on how much coffee the brewing stage requires.

Steep Time is a fixed value rather than something calculated from your inputs -- 16 hours sits within the commonly cited 12-24 hour range recommended for cold brew steeping and is used here as a single reasonable default. The calculator doesn't adjust steep time for batch size or strength, since cold brew extraction time is driven mainly by water temperature and grind size rather than by total volume.

A higher Serving Dilution Ratio means more water or milk is added per part of concentrate when you pour a finished cup, so each 8 oz serving uses up a smaller share of concentrate and a larger share of added liquid. That stretches the same Concentrate Volume across more total 8 oz servings -- but the increase tracks (1 + Serving Dilution Ratio), the total finished parts per part of concentrate, not the dilution ratio number itself, so doubling the ratio does not roughly double servings. Going from a 1:1 dilution to a 1:2 dilution only increases servings by about 50% (2 parts total becomes 3), and the increase only approaches 2x at dilution ratios far beyond this calculator's range.

Water Needed is calculated as Concentrate Volume minus Coffee Needed, which treats the coffee's mass as approximately equivalent to the water volume it displaces -- a standard simplification for a home-batch recipe calculator, not an exact volumetric measurement. In practice the difference is small enough not to meaningfully affect the recipe, but precise lab-grade brewing would need a proper density conversion.

Strong uses a 1:5 coffee-to-water ratio while Concentrate uses a denser 1:4 ratio, meaning Concentrate calls for more coffee grounds per batch than Strong does for the same Concentrate Volume. Both are stronger than Regular's 1:8 ratio and are meant to be diluted more heavily at serving time -- Concentrate is the most concentrated of the three and typically needs the highest Serving Dilution Ratio to taste balanced.