A great cold brew comes down to one number: the ratio of coffee to water. Get it right and the batch is smooth, sweet, and never bitter.

For a concentrate, start at 1:4 — one part coarse-ground coffee to four parts cold, filtered water. Dilute to taste when you serve.

Prefer it ready-to-drink from the fridge? Move to 1:8 and steep for 16–18 hours at room temperature.

Grind size matters as much as the ratio. Too fine turns the brew muddy and over-extracted; aim for a coarse, sea-salt texture.