About

Cold brew extraction relies on time and ratio rather than temperature. The standard concentrate ratio sits near 1:5 (coffee to water by weight), yielding a syrupy liquid meant for dilution at roughly 1:1 before drinking. A ready-to-drink ratio around 1:12 to 1:15 produces a smoother, less acidic result than hot-brewed coffee because fewer chlorogenic acids and oils dissolve below 25°C. Getting the ratio wrong by even 20% creates either undrinkable bitterness or weak, flat liquid - wasting expensive specialty beans. This calculator handles the arithmetic for five common methods and accounts for water absorption by ground coffee (approximately 2g water per 1g coffee), so the yield column reflects what actually ends up in your container.

Note: extraction efficiency varies with grind size, water mineral content (75 - 150 ppm TDS recommended by SCA), and ambient temperature. This tool assumes coarse grind at room temperature. Finer grinds or refrigerator steeping (2 - 5°C) will under-extract at the same steep time.

Formulas

The core calculation is a direct proportion between coffee mass and water mass governed by the chosen ratio R.

W = C × R

C = WR

Where C = mass of ground coffee, W = mass of water, and R = ratio multiplier (the water part of 1:R).

Estimated liquid yield accounts for water absorbed by the coffee grounds. Coarse-ground coffee retains approximately 2 times its dry weight in water:

Y = W − (C × A)

Where Y = liquid yield, and A = absorption factor (default 2.0). For unit conversions: 1 oz = 28.3495 g and 1 fl oz = 29.5735 ml.

Reference Data

Brew Method	Ratio (Coffee:Water)	Grind Size	Steep Time	Temperature	Dilution Before Drinking	TDS Range	Flavor Profile
Concentrate (Standard)	1:5	Extra Coarse	12 - 18 hr	Room temp	1:1 to 1:2	3.0 - 5.0%	Bold, chocolatey, low acid
Concentrate (Strong)	1:4	Extra Coarse	14 - 20 hr	Room temp	1:2 to 1:3	4.0 - 6.0%	Intense, syrupy
Ready-to-Drink (Light)	1:15	Coarse	12 - 16 hr	Room temp	None	1.0 - 1.5%	Tea-like, delicate, fruity
Ready-to-Drink (Medium)	1:12	Coarse	14 - 18 hr	Room temp	None	1.3 - 1.8%	Balanced, smooth, nutty
Ready-to-Drink (Bold)	1:8	Medium-Coarse	12 - 14 hr	Room temp	None or splash of milk	1.8 - 2.5%	Full-bodied, robust
Japanese Iced (Flash Brew)	1:15 (total)	Medium	3 - 4 min (hot)	92 - 96°C onto ice	None (ice is part of water)	1.2 - 1.5%	Bright, aromatic, acidic
Toddy System	1:5.3	Extra Coarse	12 - 24 hr	Room temp	1:1 to 1:3	2.5 - 4.5%	Clean, mellow, sweet
Mizudashi (Japanese Cold Brew)	1:13	Medium-Coarse	8 - 12 hr	Refrigerator	None	1.0 - 1.4%	Crisp, clean, light
Nitro Cold Brew Base	1:7	Coarse	16 - 20 hr	Room temp	Nitrogenated, no dilution	2.0 - 3.0%	Creamy, stout-like
Espresso-Style Concentrate	1:3	Medium	18 - 24 hr	Room temp	1:3 to 1:5	5.0 - 8.0%	Punchy, bitter-sweet
SCA Cupping Standard (ref.)	1:18.18	Medium	4 min (hot)	93°C	N/A (tasting protocol)	1.15 - 1.35%	Reference benchmark

Frequently Asked Questions

Ratio controls concentration potential, but extraction is time-dependent. At room temperature, cold brew reaches target extraction (18-22% of solubles) between 12-18 hours. Under-steeping a correct ratio yields sour, under-developed flavors. Over-steeping beyond 24 hours extracts astringent compounds regardless of ratio. The two variables are coupled: a 1:5 ratio steeped 8 hours may taste weaker than a 1:8 ratio steeped 18 hours.

Finer grinds expose more surface area, accelerating extraction. If you use medium grind instead of extra coarse at a 1:5 concentrate ratio, you risk over-extraction and bitterness within 12 hours. Compensate by either shortening steep time by 20-30% or opening the ratio to 1:6 or 1:7. The absorption factor also changes: fine grinds trap approximately 2.5× their weight in water versus 2.0× for coarse.

The ready-to-drink ratios (1:12 to 1:15) overlap with SCA hot brew recommendations (1:15 to 1:18). However, hot water extracts 20-24% of coffee solubles in 3-5 minutes, while cold water extracts 15-18% in 12+ hours. The same ratio produces different TDS and flavor profiles. For hot pour-over or drip, add 15-20% more water to the ratio this tool calculates.

The Specialty Coffee Association recommends 75-150 ppm total dissolved solids with a calcium hardness of 50-175 ppm. Distilled water under-extracts because minerals act as extraction catalysts. Hard water above 250 ppm causes chalky, flat flavors and can form calcium deposits. If using tap water above 200 ppm, a simple carbon filter brings it into range without stripping all minerals.

Ground coffee is hygroscopic and porous. Coarse grounds absorb roughly 2× their dry weight in water. For a 1:5 ratio using 100 g coffee and 500 ml water, expect approximately 300 ml of liquid yield (500 − 100 × 2 = 300). This is not waste - the absorbed water participated in extraction. Squeezing the grounds recovers some liquid but also extracts bitter compounds trapped in the cell matrix.

Undiluted concentrate stored in an airtight container at 2-5°C remains stable for 10-14 days. Oxidation and microbial growth are the limiting factors. Once diluted, consume within 3-4 days. Adding dairy or sweeteners shortens shelf life to 2-3 days. Signs of spoilage include sour aroma (distinct from intentional acidity), visible film, or off-flavors.

Yes. Refrigerator cold brew (2-5°C) extracts 25-40% slower than room temperature (20-25°C). At fridge temperatures with a 1:5 ratio, steep 18-24 hours instead of 12-16. Alternatively, keep the same steep time but tighten the ratio to 1:4. The calculator's steep time recommendations assume room temperature unless the method specifies otherwise (e.g., Mizudashi is refrigerator-based).