Cold Brew Concentrate Ratios: Strength Without Guesswork

Cold brew is usually made as a concentrate and diluted at serving, which is what makes ratios confusing. There are two ratios in play, and conflating them is the usual source of disappointment.

Brew ratio versus serving ratio

Brew ratio is coffee to water during steeping. Serving ratio is concentrate to water or milk in the glass.

A recipe stating 1:8 usually means the brew ratio, producing a concentrate intended for further dilution. Drinking that undiluted is an intense experience people sometimes mistake for a bad recipe.

Practical starting points

Working in grams is worth the trouble: 100g coffee to 800g water is unambiguous, where "a cup of coffee to four cups of water" is not.

Time interacts with ratio

Cold extraction is slow, so time does much of the work heat would otherwise do.

12-18 hours at room temperature, or 18-24 in the fridge, are reasonable ranges. Beyond about 24 hours the returns diminish and woody, papery notes start to appear.

If your cold brew tastes weak, extend time before increasing dose. If it tastes harsh or flat, shorten it.

Grind

Coarse — coarser than French press. Fine grounds over many hours over-extract and are difficult to filter out, producing a muddy result.

Consistency matters more than in almost any other method, because the long contact time exaggerates the difference between fines and boulders.

Filtering properly

Filter twice. A coarse strain first to remove the bulk, then a paper filter or fine cloth to catch fines.

Skipping the second stage is why home cold brew often tastes gritty and turns bitter in the fridge — suspended fines keep extracting.

Storage

Refrigerate and treat it as a fresh product. Concentrate keeps roughly a week or two; diluted cold brew noticeably less. It is a low-acid environment, so use judgement rather than assuming indefinite shelf life.

Dilute at serving rather than in advance, since concentrate stores better than diluted coffee.