Cold Brew Concentrate Calculator
Brew a cold brew concentrate at exactly the strength you want.
Result
How it is calculated
The ratio is written 1 : N, grounds to water by weight, and the tool treats 1 ml of water as 1 g. grounds = water / N (g). Coffee soaks up liquid, so the tool assumes the wet grounds keep about 2 ml per gram: concentrate = water − 2 × grounds (ml). Then ready = concentrate × (1 + D), where D is the parts of water or milk added per 1 part of concentrate (D = 1 means 1 : 1, D = 0 means drink it as is). A blank dilution counts as 0, but a negative dilution shows no result. Water and ratio must be above zero, and a ratio of 2 or stronger shows no result because the grounds would soak up all the water. Figures are rounded to whole grams and millilitres. The 2 ml per gram is a fixed assumption, so a very coarse or fine grind can retain a little more or less.
Worked example
1,000 ml of water at a 1 : 5 ratio, diluted 1 : 1. Grounds = 1,000 / 5 = 200 g. The grounds hold back 2 × 200 = 400 ml, so the concentrate you can pour off is 1,000 − 400 = 600 ml. Adding one part water per part concentrate gives 600 × (1 + 1) = 1,200 ml of ready-to-drink cold brew.
Common mistakes
- Reading the ratio as grounds to total drink. It is grounds to brewing water, and the dilution is a separate step afterwards.
- Expecting the concentrate to equal the water you put in. The grounds soak up roughly twice their own weight, so you pour off noticeably less.
- Entering a dilution of 1 when you mean to add half as much water as concentrate. The field is parts water per 1 part concentrate, so 0.5 is the right entry for that.
- Choosing a ratio of 2 or lower. Under this model the grounds absorb all of the water, so the tool shows no result.
- Measuring grounds by volume in scoops instead of weighing them. The ratio is by weight, and scoops of different roasts and grinds weigh differently.
About this calculator
Cold brew concentrate uses a much higher coffee-to-water ratio than hot brewing — typically between 1:4 and 1:8 by weight — steeped at room temperature or in the fridge for 12 to 24 hours, since the absence of heat means extraction relies on time instead. The result is a concentrate strong enough to be diluted, usually 1:1 with water or milk over ice, to reach normal drinking strength, and the ratio you brew at directly determines how much diluted coffee your batch will ultimately yield.
Home coffee brewers and cafés dial in this ratio because cold brew's flavour and caffeine strength are far more sensitive to the grounds-to-water ratio than to grind size or steep time within the usual range — a batch brewed too weak tastes thin even after correct dilution, while one brewed too strong wastes coffee grounds that extraction can't fully use.
This calculator takes your desired batch size and brewing ratio and returns the coffee grounds needed, the concentrate yield, and the final diluted volume, so you can dial in a batch that comes out exactly as strong as you like it.
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