Cold Brew Ratio Calculator

Background.

Cold brew is the one coffee method where the ratio on the recipe card and the drink in your glass are not the same strength, and where the volume you pour in is not the volume you get back. This calculator handles both problems. Give it any one of three things — the water your jar holds, the coffee you want to use, or the number of finished servings you need — and it returns the whole recipe, including the concentrate you will actually be able to pour off once the spent grounds have taken their share.

The brew ratio here is mass of water divided by mass of dry coffee, written 1:5 or 1:11.7. The National Coffee Association publishes 1 gram of coffee to 4 to 5 grams of water for a cold brew concentrate, steeped for approximately 12 hours, ground coarse — its own comparison is 'like rock salt' — and then diluted with water or served over ice. That 1:4 to 1:5 band is where this page starts. At the other end, Cordoba and colleagues brewed 60 grams of coffee in 700 grams of water at 20 °C for 14 and 22 hours and measured the result at about 2.0 percent dissolved solids; that is 1:11.7 and it is meant to be drunk as it comes. Anything in between is a light concentrate. The page tells you which of those three regions your ratio falls in and quotes the source rather than a house opinion.

The yield question is the one most cold brew calculators skip, and it is the reason the live Coffee to Water Ratio Calculator explicitly declines to promise a finished volume. Wet coffee grounds hold a lot of liquid. Liang, Chan and Ristenpart measured the liquid retention ratio for full immersion brewing at 2.48 plus or minus 0.19 grams of brew held per gram of dry coffee. Put 200 grams of coffee into a litre of water and roughly half a litre of that water never comes out of the filter. This page computes that loss explicitly, subtracts it, and reports what remains — because a recipe that says 'one litre of water' and a jar that produces 545 millilitres of concentrate are both correct, and only one of them tells you whether you have enough for the week.

Be aware of one honest limitation, stated here rather than buried in a FAQ: Liang and colleagues measured retention while brewing hot, at 80 to 99 °C. No peer-reviewed measurement of retention for room-temperature immersion turned up during this build. Back-solving Cordoba's cold brew from their own three published numbers implies retention nearer 1.88 grams per gram, which is plausible — cold water, a coarser grind and no compressed filter bed would all reduce it. Rather than pick silently, this page exposes the retention ratio as an editable field, defaults to the only value it can cite from a direct measurement, and names the alternative in the field's own hint. At 200 grams of coffee the two figures differ by 120 grams of concentrate, so the choice matters and you should know you are making it. The cheapest fix is empirical: weigh one batch of poured-off concentrate, divide, and enter your own number once.

Strength is reported twice, for the concentrate and for the glass, as total dissolved solids. Both come from the equilibrium relation Liang and colleagues derive, and both are estimates. Published cold brew strength figures disagree by roughly fifteen percent depending on how extraction yield was measured, and that disagreement is printed beside the numbers. A refractometer on your own concentrate settles it in seconds.

Two things this page deliberately does not do. It computes no caffeine figure — caffeine per gram of coffee depends on species, roast level and how far the extraction went, and the Coffee Calculator and Coffee Kick Calculator own that question. And it does not compute steep time, because steep time is not a function of the ratio; the sourced figures, roughly 12 hours from the NCA and 14 to 22 hours from Cordoba's trials at 20 °C, sit beside the result for reference.

What is cold brew ratio calculator?

A cold brew ratio calculator converts between the three quantities that define a cold brew recipe — dry coffee weight, brew water weight, and the number of finished servings — using the brew ratio as the link. Cold brew is a full immersion method: coarse grounds sit in room-temperature or cold water for hours, and the resulting liquid is either drunk as it is or, far more commonly, brewed as a concentrate and diluted at the point of service.

What makes cold brew arithmetic different from hot brewing is that the concentrate ratios in normal use are so tight — the National Coffee Association publishes 1:4 to 1:5 — that the liquid the spent grounds retain is a large fraction of everything you poured in. At 1:5, roughly half the water stays in the grounds. This calculator models that loss explicitly using the liquid retention ratio measured by Liang, Chan and Ristenpart, reports the concentrate you can actually pour off, and then applies your dilution to get the strength and volume of the finished drink.

It also reports total dissolved solids for both the concentrate and the glass, from the equilibrium relation between extraction yield, brew ratio and strength published in the same paper. Those strength figures are estimates and the page says so beside them; the coffee and water doses are not estimates, they are arithmetic.

How to use this calculator.

1. 01Pick which of the three things you know: the water your jar holds, the coffee you want to use, or the finished servings you need.
2. 02Enter that quantity by weight. Cold brew is a mass ratio and a scale is the whole point — volume scoops of coarse grounds vary far too much to be useful.
3. 03Set the brew ratio. Use 4 to 5 for a concentrate you will dilute (the National Coffee Association's published range), or around 11.7 for a ready-to-drink brew like the one Cordoba et al. measured. Read the band label to confirm which regime you have chosen.
4. 04Set the dilution. 1 means one part water, milk or melted ice per part concentrate. Use 0 if you are brewing at a ready-to-drink ratio and will not dilute.
5. 05Read the coffee and water doses — those are exact arithmetic — then read the concentrate yield, which is an estimate that depends on the retention ratio.
6. 06The first time you brew, weigh the concentrate you actually pour off, divide the shortfall by your coffee weight, and enter that as your own retention ratio. Every subsequent yield prediction will be right for your equipment.
7. 07Treat the TDS figures as a starting point and adjust to taste. Steep time, grind size and coffee origin all move strength independently of the ratio.

The formula.

The brew ratio is defined as R = M_w / M_g, mass of water over mass of dry coffee — Liang, Chan and Ristenpart's definition, and the same one behind the 1:X notation on the hot-brew page. Whichever of the three modes you use, the calculator's first job is to pin down both M_g and M_w, because once both are known every other output follows. From brew water, M_g = M_w / R. From coffee weight, M_w = M_g × R. From servings, the finished volume is divided by (1 + dilution) to get the concentrate needed, and then by the net factor below to get the coffee.

Extraction yield E is the fraction of the dry coffee mass that dissolves, counted on a solution basis — solids wherever they end up, including inside the liquid the grounds retain. Total dissolved solids then follow from a mass balance: solids are E × M_g and the whole solution weighs M_w + E × M_g, so TDS = E / (R + E). That is exactly the relation Liang and colleagues publish as E = (TDS / (1 − TDS)) × R, rearranged. Note what it means: TDS depends only on the ratio and the yield, never on batch size, so 20 g and 2 kg of coffee at 1:5 give the same strength.

The grounds retain R_ret grams of brew per gram of dry coffee, so retained liquid is R_ret × M_g and the concentrate you can pour off is Y = M_g × (R + E − R_ret). Everything hangs on that net factor. With the worked example's numbers — R = 5, E = 0.207, R_ret = 2.48 — the net factor is 2.727, so 200 g of coffee returns 545.4 g of concentrate out of 1000 g of water in. Cross-check it the long way: the solution weighs 1000 + 41.4 = 1041.4 g, the grounds keep 2.48 × 200 = 496 g, and 1041.4 − 496 = 545.4 g. The two routes agree, and a test asserts they always will.

If the net factor is zero or negative the grounds would absorb everything and there would be no drink. That is reachable from values the form itself allows — a brew ratio of 3 with a retention ratio of 3.5 — so the calculator raises a typed error on the brew ratio rather than returning a negative yield.

Dilution is a mass balance too and it is exact: adding d parts of water per part of concentrate multiplies the volume by (1 + d) and divides TDS by (1 + d). The worked example's 3.9754177069 percent concentrate becomes 1.9877088535 percent in the glass at 1:1, and 545.4 g of concentrate becomes 1090.8 mL of drink — 4.545 servings of 240 mL.

Nothing is rounded at an intermediate step. Every quantity is carried at full precision and rounded once, at the end, to ten decimal places. The band label is decided from the unrounded brew ratio, so a value of 5.0000000001 is classified as a light concentrate even though the label prints it as 1:5.0.

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.