Cold Brew Ratio Calculator

Background.

Fill a one-litre jar with 1,000 g of water, stir in 200 g of coarse coffee, leave it overnight and strain it in the morning. You will pour off roughly 545 g of concentrate — little more than half of the water you started with. Nothing went wrong. Wet coffee grounds hold a great deal of liquid, and at the tight ratios used for cold brew concentrate the coffee bed is large enough to keep almost as much as you recover. The 2.48 g of brew retained per gram of coffee used here comes from Liang, Chan and Ristenpart's measurements of immersion brewing — made with hot water, as it happens, because no cold-water figure has been published, which is why you can replace it with your own figure once you have weighed a batch.

The ratio decides what kind of drink you are making. The National Coffee Association gives 1 g of coffee to 4–5 g of water for a concentrate, steeped about 12 hours with a grind like rock salt and then cut with water or poured over ice. At the other end, Cordoba and colleagues brewed 60 g of coffee in 700 g of water — 1:11.7 — at 20 °C and measured about 2% dissolved solids, a strength meant to be drunk as it is. Anything between those is a light concentrate that wants only a splash of dilution, if any.

You can start from whatever limits you: the water your jar holds, the coffee left in the bag, or the number of glasses you need for the week. Each route returns the full recipe — coffee and water by weight, the liquid the grounds will keep, the concentrate you can pour off, and how strong and how plentiful the drink is once diluted.

What is cold brew ratio calculator?

A cold brew recipe is set by its brew ratio: grams of water divided by grams of dry coffee, written 1:5 or 1:11.7. It is a mass ratio, so a kitchen scale beats any scoop of coarse grounds. Three more quantities follow from it. Extraction yield is the share of the coffee's own mass that dissolves — about 21% at equilibrium in Liang and colleagues' work — counted wherever those solids end up, including in the liquid trapped in the spent grounds. Total dissolved solids, or TDS, is the dissolved coffee as a percentage of the liquid's mass, the standard measure of strength: a 1:5 concentrate sits near 4%, a ready-to-drink cold brew near 2%. The retention ratio is the grams of brew the wet grounds hold back per gram of dry coffee, and it is what separates the water you pour in from the concentrate you get out.

How to use this calculator.

1. 01Choose your starting point: the water your vessel holds, the coffee you have, or the finished servings you want.
2. 02Enter that amount by weight. For water, millilitres and grams are interchangeable — 1,000 mL weighs 1,000 g.
3. 03Set the brew ratio: 4 to 5 for a concentrate you will dilute, around 11.7 for a brew to drink straight. The band label confirms which you have chosen.
4. 04Set the dilution in parts added per part of concentrate — 1 for the classic half-and-half pour, 0 for a ready-to-drink brew — and the size of one serving.
5. 05Leave retention at 2.48 and extraction yield at 20.7 for a first batch. Afterwards, weigh the concentrate you actually poured off and enter your own retention figure.
6. 06Read the coffee and water doses, then the concentrate yield, strength and servings, keeping in mind that the last three are estimates.

The formula.

Liang, Chan and Ristenpart define the brew ratio as R = M_w ÷ M_g, water mass over dry coffee mass. Starting from water, the coffee is M_g = M_w ÷ R; starting from coffee, the water is M_w = M_g × R. Strength follows from a mass balance. If E is the extraction yield as a fraction, the dissolved solids weigh E × M_g and the whole solution weighs M_w + E × M_g, so TDS = E ÷ (R + E) — the same relation Liang and colleagues publish as E = TDS ÷ (1 − TDS) × R, rearranged. Batch size cancels out: 20 g or 2 kg of coffee at 1:5 give the same strength. The grounds keep R_ret × M_g of that solution, so the concentrate you can pour off is Y = M_g × (R + E − R_ret). Starting from servings, the calculation runs backwards: servings × serving size gives the finished drink, dividing by (1 + dilution) gives the concentrate needed, and dividing again by (R + E − R_ret) gives the coffee. Dilution is exact on a mass basis — adding d parts per part of concentrate multiplies the volume by (1 + d) and divides TDS by the same factor. Volumes are reported at 1 g = 1 mL; a 4% concentrate is closer to 1.01 g/mL, so millilitre figures run about 1% high. If R + E − R_ret is zero or less, the grounds would soak up every drop and no concentrate would be left, so such a combination is refused; at the default retention it needs a ratio below 2.273. The strength label compares the ratio with the published figures: below 1:4 thicker than the NCA range, 1:4 to 1:5 concentrate, up to 1:11.7 light concentrate, and 1:11.7 or above ready to drink.

A worked example.

Frequently asked questions.

References& sources.

1. [1]National Coffee Association of U.S.A. "Cold brew coffee." aboutcoffee.org — publishes the 1:4 to 1:5 coffee-to-water ratio, the approximately 12-hour contact time, the coarse 'like rock salt' grind, and that the concentrate is designed to be diluted with water or served over ice.
2. [2]Liang J, Chan KC, Ristenpart WD (2021). "An equilibrium desorption model for the strength and extraction yield of full immersion brewed coffee." Scientific Reports 11:6904, doi:10.1038/s41598-021-85787-1 (CC BY 4.0) — source of the brew-ratio definition R_brew = M_w/M_g, the liquid retention ratio 2.48 ± 0.19 g per g of dry coffee, the relation E = (TDS/(1−TDS)) × R_brew, and the equilibrium extraction yield of 20.70 ± 1.08%. Brewing in that study was hot, 80–99 °C.
3. [3]Cordoba N, Pataquiva L, Osorio C, Moreno Moreno FL, Ruiz RY (2019). "Effect of grinding, extraction time and type of coffee on the physicochemical and flavour characteristics of cold brew coffee." Scientific Reports 9:8440, doi:10.1038/s41598-019-44886-w (CC BY 4.0) — 60 g ground coffee per 700 g water at room temperature (20 °C), 14 and 22 hours, coarse grind 701–900 µm, measured TDS 2.04% and extraction yield 20.39%. Source of the 1:11.7 ready-to-drink reference.
4. [4]Specialty Coffee Association. "Water and Coffee Acidity: How to Adapt Your Water for Different Extraction Methods" (25 Magazine, issue 9) — identifies 60 grams per litre as the most common way to write a hot drip or immersion brewing ratio. Cited here only to mark where the hot-brew page's scope ends and this page's begins.
5. [5]National Institute of Standards and Technology. NIST Special Publication 811, 2008 edition, "Guide for the Use of the International System of Units (SI)" — the exact conversions behind the ounce and fluid-ounce outputs: 1 avoirdupois ounce = 28.349523125 g, 1 US fluid ounce = 29.5735295625 mL.
6. [6]U.S. Food and Drug Administration (Consumer Updates). "Spilling the Beans: How Much Caffeine is Too Much?" — an 8-ounce cup of coffee is closer to 80 to 100 milligrams of caffeine, and 400 mg a day is cited as an amount not generally associated with negative effects for most healthy adults. Cited only to support this page's decision to print no caffeine figure of its own.