The Cold Brew Formula
Cold brew is built on one simple ratio: ground coffee to water by weight. The formula is coffee = water divided by the ratio number. Because one millilitre of water weighs about one gram, you can treat millilitres and grams interchangeably, so 1000 ml of water at a 1:5 ratio needs 200 g of coffee. Lower numbers make a strong concentrate you dilute before drinking; higher numbers make a ready-to-drink brew. Use a coarse grind, steep in the fridge, then filter out the grounds.
Cold Brew Ratio Chart
These are coffee amounts per 1 litre (about 34 fl oz) of water:
| Ratio | Type | Coffee per 1 L | How to use |
|---|---|---|---|
| 1:4 | Strong concentrate | 250 g | Dilute 2:1 or more |
| 1:5 | Standard concentrate | 200 g | Dilute about 1:1 |
| 1:8 | Mild concentrate | 125 g | Dilute lightly to taste |
| 1:15 | Ready to drink | 67 g | Drink as-is over ice |
| 1:16 | Ready to drink | 63 g | Regular coffee strength |
Concentrate vs Ready-to-Drink: A Strength Guide
A concentrate (ratios from 1:4 to about 1:8) is brewed strong on purpose so it stores well and stretches further; you cut it with water, milk, or ice before drinking, usually around one part concentrate to one part liquid. Ready-to-drink cold brew (1:15 to 1:16) is brewed at normal coffee strength and poured straight over ice. Concentrate is the better choice for batch prep and iced lattes, while ready-to-drink is simplest for grab-and-go. Either way, a coarse grind and a 12 to 24 hour fridge steep give the smooth, low-acid cup cold brew is known for.
Frequently Asked Questions
How much coffee do I need for cold brew? Divide your water by the ratio. At a 1:5 concentrate, 1 litre of water needs 200 g of coffee.
Should I make concentrate or ready-to-drink? Concentrate stores better and is great for lattes; ready-to-drink is easiest to pour straight over ice.
How long should cold brew steep? 12 to 24 hours in the fridge; 16 to 18 hours is a reliable sweet spot.
What grind size works best? Coarse, like raw sugar. Fine grounds over-extract and slip through the filter.