Cold Brew Coffee Ratio Calculator
Calculate the perfect coffee-to-water ratio for cold brew concentrate or ready-to-drink cold brew.
Get amounts in grams, ounces, and milliliters.
What Is Cold Brew Coffee?
Cold brew is made by steeping coarsely ground coffee in cold or room-temperature water for an extended period, usually somewhere between 8 and 20 hours depending on how much coffee you loaded in. The result is smoother and less acidic than hot-brewed coffee. It is often described as more caffeinated, and undiluted concentrate certainly is. Even after you cut it with water or milk, a normal glass still tends to land around twice an ordinary cup of drip, so treat it as a strong drink rather than a like-for-like swap.
Brew Ratios Explained
The ratio is coffee : water by weight, which is how every serious coffee recipe is written. 1:8 means 1 gram of ground coffee for every 8 grams of water, and since 1 ml of water weighs 1 g you can read those grams straight off a measuring jug.
This matters more than it sounds. Ground coffee is only about a third the density of water, near 0.36 g per ml, so a ratio read as volume rather than weight leaves you with roughly a third of the coffee you intended and a thin, sour brew. If a recipe does not say which it means, assume weight.
| Ratio | Type | Use |
|---|---|---|
| 1:4 | Strong concentrate | Dilute 1:1 before drinking |
| 1:5 | Standard concentrate | Dilute 1:1 or 1:2 |
| 1:8 | Mild concentrate | Still worth cutting, about 1:0.5 |
| 1:10 | Ready-to-drink | Pour over ice as it is |
| 1:15 | Japanese-style light | Drink straight, closest to iced drip |
Plenty of recipes call 1:8 “ready to drink”. Run the numbers and it is not: the grounds hand back less liquid than the water you poured in, so an eight-ounce glass of neat 1:8 carries roughly four ordinary cups’ worth of caffeine. Ready-to-drink starts nearer 1:10, and the light Japanese style at 1:15 is the one that genuinely drinks like iced coffee.
How Much Do You Actually Get Back?
Less than you put in. Wet grounds hold onto roughly 2 ml of liquid per gram of coffee, and that liquid stays in the filter. Brew 1,000 ml of water at 1:8 and you use 125 g of coffee, which keeps about 250 ml, leaving you around 750 ml in the jar. The calculator shows all three numbers so nothing surprises you at the straining stage.
Steep Time
Fridge times, since that is how most people brew it. A heavier dose of coffee needs longer to give up what it holds, so the strong ratios sit at the top of the range.
| Ratio | Fridge steep |
|---|---|
| 1:4 strong concentrate | 16–20 hours |
| 1:5 standard concentrate | 14–18 hours |
| 1:8 mild concentrate | 12–16 hours |
| 1:10 ready-to-drink | 10–14 hours |
| 1:15 Japanese-style light | 8–12 hours |
At room temperature knock roughly a third off, and watch it more closely: warm cold brew over-extracts into something woody far more easily than a fridge batch does. Either way it is a slow process. Pull a fridge batch before about eight hours and it comes out weak and sour no matter how much coffee you used.
Grind Size
Use an extra-coarse grind, a step coarser than you would for a French press. Think cracked peppercorns rather than sea salt. Fine grinds over-extract and make the brew bitter. They also clog filters and make straining difficult.
Serving Concentrate
Concentrate is typically diluted 1:1 with:
- Cold water (lightest, preserves flavor)
- Milk or cream (richer, smoother)
- Oat milk or almond milk (popular dairy-free option)
Cold brew keeps in the fridge for up to 2 weeks in a sealed container.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.