Cold Brew Calculator - Coffee Ratio for Concentrate and Ready-to-Drink

Three methods, three ratios, one rule - time replaces heat

Cold brew skips hot water entirely. Instead of extracting flavor in 2-4 minutes with near-boiling water, you steep coarsely ground coffee in cold water for 12-24 hours. The slow extraction pulls sweetness and body while leaving most of the bitter compounds behind. This calculator covers three cold brew methods - concentrate (1:5), ready-to-drink (1:8) and Japanese iced flash brew (1:7 with hot water on ice) - and lets you calculate from coffee weight, water volume or number of servings.

How to make cold brew - step by step

Choose your method - concentrate (strong, dilute before drinking, keeps 14 days), ready-to-drink (drink as-is, keeps 7 days) or Japanese iced (hot water on ice, ready in 3 minutes).
Select your starting point - how much coffee you have, how big your container is (water volume) or how many servings you need.
Enter the amount - the calculator computes the other side of the ratio automatically.
Optionally set steep time - 8 hours (milder), 12 hours (classic), 16 hours (stronger) or 24 hours (very bold). Default is automatic by method.
Read your recipe - coffee grams, water ml, grind size, steep time, step-by-step instructions and storage advice.

Cold brew method atlas

A side-by-side reference for all three methods. Each card shows the key parameters at a glance.

1:5

Concentrate

Grind: coarse
Time: 16-24 h
Temp: cold (fridge)
Dilute 1:1
Keeps: 14 days

1:8

Ready-to-drink

Grind: coarse
Time: 12-16 h
Temp: cold (fridge)
No dilution
Keeps: 7 days

1:7

Japanese iced

Grind: medium-fine
Time: 2-4 min
Temp: 92-96 C
60% hot + 40% ice
Serve immediately

Ratio reference table

Quick-reference amounts for common batch sizes. All values rounded to the nearest gram.

Batch size	Concentrate (1:5)	Ready-to-drink (1:8)	Japanese iced (1:7)
250 ml (1 cup)	50 g	31 g	36 g
500 ml (2 cups)	100 g	63 g	71 g
1 L (4 cups)	200 g	125 g	143 g
1.5 L (6 cups)	300 g	188 g	214 g
2 L (8 cups)	400 g	250 g	286 g

Steep time vs flavor profile

Steep time	Flavor	Best for
8 hours	Light, tea-like, subtle sweetness	Light roasts, single-origin beans
12 hours	Balanced, smooth, chocolate notes	Most coffees - the gold standard
16 hours	Bold, full-bodied, slight bitterness	Dark roasts, concentrate batches
24 hours	Very strong, bitter edge, intense	Concentrate only - always dilute

Practical examples

Example 1: Concentrate, 100 g coffee, automatic time
Result: 500 ml water, steep 16-24 h, yields 1 L finished drink after 1:1 dilution (~4 servings). Coarse grind. Keeps 14 days.

Example 2: Ready-to-drink, 500 ml water, 12 hours
Result: 63 g coffee, steep 12 h, yields 500 ml finished drink (~2 servings). Coarse grind. Keeps 7 days.

Example 3: Japanese iced, 4 servings
Result: 143 g coffee, 600 ml hot water + 400 g ice, ready in 3 minutes. Medium-fine grind. Serve immediately.

Example 4: Concentrate, 50 g coffee
Result: 250 ml water, yields 500 ml finished drink after dilution (~2 servings). Good for a Mason jar batch.

Example 5: Ready-to-drink, 8 servings (2 L), 16 hours
Result: 250 g coffee, 2000 ml water, steep 16 h for a bolder batch. Needs a large pitcher or French press.

FAQ - Frequently asked questions

What is the difference between cold brew and iced coffee?

Iced coffee is regular hot-brewed coffee poured over ice. Cold brew is never heated - coffee steeps in cold water for 12-24 hours. The result tastes fundamentally different: cold brew is smoother, sweeter and 67% less acidic than iced coffee because cold water extracts fewer bitter and acidic compounds.

Should I use the fridge or room temperature?

Both work. Room temperature (20-22 C) extracts faster - you can cut steep time by 30-40% (8-12 h instead of 16-24 h). Fridge temperature (4-6 C) extracts slower but produces a smoother, less bitter result. Most recipes default to fridge. If you steep at room temp, start checking at 8 hours.

What grind size should I use for cold brew?

Coarse - like beach sand or raw sugar. Fine grinds over-extract during the long steep and produce bitter, muddy coffee. They also clog filters. If you do not have a grinder, ask your coffee shop to grind for "cold brew" or "French press" - both are coarse. Exception: Japanese iced uses medium-fine (like drip) because the brew time is only 3 minutes.

How long does cold brew last in the fridge?

Concentrate (undiluted) keeps up to 14 days sealed in the fridge. Ready-to-drink cold brew is best within 5-7 days. After that, flavor degrades - it does not spoil dangerously, but it starts tasting stale and flat. Once you dilute concentrate, treat it like ready-to-drink (7 days max).

What is Japanese iced coffee and how is it different from cold brew?

Japanese iced coffee (flash brew) uses hot water dripped directly onto ice. The hot water extracts flavor in 2-4 minutes (like pour-over), and the ice instantly cools the coffee. The result has brighter, more acidic flavors compared to cold brew's smooth sweetness. It is the best method for single-origin light roasts where you want to taste origin characteristics.

Can I use any coffee for cold brew?

Yes, but medium to dark roasts work best. Cold extraction emphasizes sweetness and chocolate/caramel notes while suppressing acidity. Light roasts can taste thin and flat in cold brew because their bright, fruity notes need heat to develop. For light roasts, use Japanese iced instead - it preserves those flavors. Pre-ground supermarket coffee works fine for cold brew - grind consistency matters less with a 12+ hour steep.

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Ready-made calculations

The most searched variants of this calculator. Each link opens it with the value already filled in, ready to calculate.