Cold Brew Coffee Dilution Calculator

Cold Brew Coffee Dilution

Cold brew uses long steep times and cold water to extract a smooth, low-acid coffee. Two main styles:

1. Concentrate (1:4 to 1:8 ratio), meant to be diluted with water, milk, or mixers 2. Ready-to-drink (1:10 to 1:15 ratio), pour over ice, no dilution needed

Standard recipes:

Dilution rule of thumb: Concentrate ratio (1:N) → drink at 1:(2N) ratio

So 1:5 concentrate diluted 1:1 with water = 1:10 final ready-to-drink strength.

Caffeine, worked from the beans rather than the ratio

Start from the coffee, not from how much water you added. Roasted arabica is about 1.2% caffeine by weight, and a long cold steep pulls most of it out, so reckon on roughly 10 mg of caffeine per gram of dry coffee ending up in the liquid. Treat that as an estimate rather than a measurement: grind, steep length and bean origin all move it, and robusta carries roughly double the caffeine of arabica. What does not move is the ceiling. A 100 g batch holds about 1,000 mg however you dilute it, because diluting spreads the same caffeine over more volume and does not create any.

That gives figures like these:

• Standard concentrate (1:5), undiluted: roughly 100 mg per fluid ounce
• Mild concentrate (1:8), undiluted: roughly 50 mg per fluid ounce
• The same 1:8 concentrate cut two parts water to one: roughly 17 mg per fluid ounce

For comparison, an ordinary 8 oz cup of drip is about 95 mg, and a 16 oz Starbucks cold brew is around 205 mg. If a cold brew calculator ever tells you a single drink carries a thousand milligrams, check its arithmetic: that would be two and a half times the FDA’s 400 mg daily ceiling in one glass, and more caffeine than the coffee in the jug actually contained.

A realistic 12 oz iced coffee: 4 oz of 1:8 concentrate topped with 8 oz of water or milk lands near 200 mg, so about twice a regular cup. That is a strong drink, not a dangerous one.

Dilution math

The grounds keep some of your water. Wet coffee holds roughly 2 g of liquid per gram of dry grounds, and at concentrate ratios that is a large slice of the batch, which is why a jug always yields less than the water you poured in.

Concentrate yield = brew water − (2 × coffee weight) Final volume = concentrate yield × (1 + dilution factor)

Example, 100 g coffee at 1:5:

• Brew water 500 g, grounds keep about 200 g, so you pour off roughly 300 g of concentrate
• Diluted equal parts, that becomes 600 g of finished drink
• Diluted 1:0.5, 450 g

Brewing tips:

• Use coarse grind (coarser than French press): fine grinds make muddy concentrate
• Filter twice: paper filter after the steep, then chill 4-6 hours for crystal-clear yield
• Refrigerate concentrate up to 2 weeks
• Diluted batches drop in flavor after 5-7 days

Why cold brew is smoother: Cold water doesn’t extract chlorogenic acids efficiently. The result: 60-70% less perceived acidity vs. iced hot-brewed coffee, with a sweeter, fuller mouthfeel — but you also miss some flavor compounds that only emerge above 90°C.