Cold Brew Ratio

What cold brew is (and is not)

Cold brew steeps coarse coffee in cold water for many hours, then filters. It is not iced hot coffee. It is also not a caffeine calculator. Dose and dilution decide strength. Species and roast decide a lot of the stimulant load.

Two kitchen styles matter. Concentrate is mixed later with water or milk. Ready-to-drink is steeped at a drinkable strength so you can pour it over ice without guessing a dilution.

Twelve to 18 hours is the steep window the widget prints. Filter at 12 if it already tastes strong. Do not push past 18 hoping for espresso. You will get sludge.

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How to use this calculator

Enter water grams and pick concentrate (1:5) or ready to drink (1:8). Default water is 800 g.

Coffee grams = water ÷ 5 for concentrate, or water ÷ 8 for ready. The default concentrate run is 160 g coffee. The same water as ready-to-drink is 100 g coffee. Steep 12 to 18 hours in the refrigerator.

Switch the style dropdown before you shop beans. A 1:5 shop list is 60% more coffee than 1:8 at the same water. That is a budget line, not a flavor flex.

Use cold water from the tap or fridge, not leftover kettle water. You want the jar to start cold so it does not linger in the danger zone while it chills down.

Concentrate is not a ready drink. Dilute 1:1 or 1:2 with water or milk before serving. Taste a teaspoon first. Kids should not get a concentrate mug by accident. Caffeine is still not computed here.

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Formula and worked examples

Concentrate: coffee = water ÷ 5. Ready: coffee = water ÷ 8. Steep window printed by the widget: 12 to 18 hours cold.

1,000 g water as concentrate needs 200 g coarse coffee. After filtering you still have a strong jug. A common serve is 1 part concentrate to 1 or 2 parts water or milk. That serve step is not inside the widget.

1,000 g water as ready-to-drink needs 125 g coffee. Pour over ice. Ice will melt and dilute further, so some people brew ready at 1:7 in hot weather. This tool stays on 1:8.

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Why coarse and cold

Fine grinds over-extract bitterness during a 16-hour steep and clog filters. Coarse grinds keep sediment down and slow extraction so the long time does not shred the cup.

Cold water extracts a different mix of acids and aromatics than 200 °F drip. That is a flavor fact, not a safety claim. The jar still needs refrigeration because you are holding a wet food for half a day.

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Water batches you can make tonight

Weigh water into a jar, add the coffee mass, stir once to wet the bed, cover, and refrigerate. Filter with a paper cone, cloth, or metal mesh. Do not leave the steep on a 75 °F counter overnight if you can use the fridge.

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Food safety for a long steep

USDA's danger zone is 40 °F to 140 °F. A counter steep in a warm kitchen sits in that zone for 12 hours. Use the refrigerator.

Once filtered, treat concentrate like other perishable beverages if you add milk, or like a leftover if it sits out at a brunch. Two hours is the room-temperature limit, one hour above 90 °F. Leftovers that you reheat (unusual for coffee, common for coffee-based sauces) go to 165 °F.

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Dilution, kids, and caffeine scope

Concentrate poured neat is a strong adult drink. If a teenager drinks coffee in your house, dilute first. AAP materials still advise that children do not need caffeine.

This page will not estimate milligrams. Cold brew can be higher or lower in caffeine than drip depending on dose, time, and whether you serve concentrate. Use HealthCalc for daily caffeine math.

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How long the jug keeps

Filtered concentrate in a covered jar in the fridge is a leftover-style product. Plan to finish it within a few days. Flavor fades before most safety clocks if the jar was clean and cold the whole time.

Discard a batch that smells sour in a rotten way, shows mold, or sat out overnight. Coffee's roasted smell can hide early spoilage when milk was added.

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Grind, brew yield, and sludge

Coffee absorbs water. The liquid you pour off is less than the water you started with. The calculator doses the steep, not the finished ounces in the pitcher.

Press the grounds lightly. Squeezing a cloth filter hard dumps fines and bitterness into a concentrate you then cannot un-extract.

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What to do after you filter the jar

Concentrate at 1:5 is a base. A 160 g coffee / 800 g water steep might yield about 600 to 700 g of liquid after the grounds keep water. Yield varies with grind and how hard you press.

If you serve 200 g of that concentrate with 200 g water, you have roughly a 1:10 beverage relative to the original dry coffee still sitting in the compost, not a new brew ratio. Parents who want a milder glass should start 1:1 concentrate to water and adjust.

Milk drinks hide bitterness. They also hide how much coffee a teenager poured. Use a measuring cup for the concentrate if caffeine is a household issue, then stop. This page still will not output milligrams.

Label the jar with the start time and the style (1:5 or 1:8). A roommate will otherwise drink ready-to-drink as if it were concentrate, or the reverse.

Ice is water. A 1:8 ready brew over a full glass of ice can taste like 1:10 by the last third. Brew a hair stronger only if you always serve over ice. The widget stays on 1:8.

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Jars, filters, and the mess after 16 hours

A 1-liter mason jar holds about 800 g of water plus coffee only if you leave headspace. The default 800 g water plus 160 g coffee will sit high in a quart jar. Use a half-gallon jar for that batch, or drop water to 600 g (120 g coffee at 1:5).

Cloth filters need a rinse and a boil now and then or they sour. Paper cones are disposable and keep sediment down. Metal mesh is fast and silty. Silt is not unsafe. It is muddy.

Do not grind espresso-fine for a 16-hour steep. You will get a bitter sludge that clogs every filter in the drawer. Coarse like breadcrumbs.

If you travel with a loaded jar in a cooler, keep it on ice the way you would keep milk. A warm trunk for 6 hours is a danger-zone steep, not cold brew.

Kids should not shake the jar for fun. Oxygen and agitation speed extraction of harsh bits and can leak. A single stir at the start is enough.

Spent grounds go in compost, not down the sink. They clog disposals. The calculator does not estimate trash weight. Expect the wet grounds to weigh more than the dry coffee you started with.

If you want sparkling cold brew, carbonate the water you use to dilute concentrate, not the steep itself. Gas and a 16-hour jar is a mess.

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Limits

Toddy-style commercial ratios and Japanese ice-drip towers use different numbers. Japanese iced coffee is hot brew over ice, not this method.

Decaf still uses the same 1:5 or 1:8 mass ratio. The widget cannot see a decaf bag.

Nitro taps and canned cold brew are commercial products with their own labels. Do not reverse-engineer their milligrams of caffeine from this steep math.

If the fridge died overnight, throw the steep away. A 16-hour counter accident in a warm kitchen is a food-safety decision, not a flavor one.

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How it works

Coarse grind, room-cold water, long contact time. Dilute concentrate with water or milk before serving to kids only if you intend them to have coffee at all.

Frequently asked questions

• Is cold brew lower caffeine?

  Not reliably. Dose and dilution dominate. This tool does not estimate caffeine.

Related calculators

References

1. SCA. Specialty Coffee Association
2. AAP HealthyChildren. Caffeine: a primer for parents
3. USDA. FoodData Central
4. SCA. SCA brewing research and standards
5. USDA FSIS. Danger Zone (40 °F to 140 °F)
6. USDA Ask FSIS. 2 Hour Rule
7. USDA FSIS. Leftovers and food safety
8. FDA. Spilling the beans: how much caffeine is too much?
9. USDA FSIS. Safe minimum internal temperature chart