Coffee to Water Ratio

What a coffee-to-water ratio is

A brew ratio is coffee mass to water mass. 1:16 means 1 gram of coffee for every 16 grams of water. Strength (how concentrated the cup tastes) and extraction (how much of the dry coffee dissolved) are related but not identical.

This page sizes a pot. It is not a daily caffeine limit and it does not estimate milligrams of caffeine. That job lives on HealthCalc.

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How to use this calculator

Enter cups of water, using 240 g (240 mL) per cup, and a ratio 1:x. Defaults are 2 cups and 1:16.

Coffee grams = water grams ÷ ratio. Water grams = cups × 240. The default run is 480 g water and 30 g coffee.

Type 1:17 or 1:18 if you want to sit on the 55 to 60 g per liter SCA band. Type 1:16 if your household already likes a stronger mug. Stay inside 8 to 22. The field will not let you go espresso-low.

Weigh beans, then grind. If you weigh after grinding you lose a gram in the grinder. For a 15 g single mug that gram is 7% of the dose.

This page sizes a pot. It does not estimate milligrams of caffeine. If you need a daily caffeine cap, that lives on HealthCalc. Keep this tool for brew ratio only. Parents packing thermoses can still use the same 1:16 math for a travel mug by entering 1 cup of water.

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Formula, SCA range, and a worked example

waterG = cups × 240. coffeeG = waterG ÷ ratio.

Specialty Coffee Association brewing guidance clusters near 55 g of coffee per liter of water, with a published Golden Cup ratio of 55 g/L ± 10%. Sixty grams per liter is about 1:16.7. Fifty-five grams per liter is about 1:18.2. A home 1:16 ratio is a bit stronger than the 55 g/L center.

Four cups at 1:17: water 960 g, coffee 56.5 g. That sits next to 55 to 60 g per liter (960 mL is 0.96 L; 55 × 0.96 = 52.8 g, 60 × 0.96 = 57.6 g).

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Ratios versus grams per liter

Pick the ratio that matches how you already brew, then change grind and time before you chase a new ratio. A finer grind extracts faster. A coarser grind extracts slower.

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Water temperature and contact time

Golden Cup brewing practice puts water at the coffee near 200 °F ± 5 °F (about 93 °C). Contact time depends on grind: roughly 1 to 4 minutes for fine, 4 to 6 for drip, 6 to 8 for coarse.

A home drip machine that brews too cool will taste sour even if the ratio is perfect. Ratio cannot fix a 170 °F brew cycle.

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Why scoops fail

A "tablespoon of coffee" is a volume. Dark roasts are less dense than light roasts. Two households using the same scoop can be 20% apart in dose.

USDA FoodData Central lists ground coffee in grams for nutrition portions. Those household weights are not a brew recipe. Weigh the dose this calculator prints.

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Kids, pregnancy, and why caffeine is out of scope

American Academy of Pediatrics guidance treats caffeine as a stimulant that children do not need. This tool will still do the brew math if you type cups. It will not tell you whether a child should drink the pot.

If you need milligrams per day, use a caffeine calculator. Do not multiply coffee grams here by a guessed caffeine percent. Roast, species, and brew method move that number.

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Holding brewed coffee

Brewed coffee is low-acid enough that people leave carafes out. Flavor dies on a hot plate. For milk drinks, the dairy follows USDA perishable rules: 2 hours at room temperature, 40 °F storage, 1 hour if the room is above 90 °F.

Cold leftover coffee used in ice cubes is a flavor choice. If you added milk, treat it as a leftover beverage and refrigerate promptly.

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Grind, filter, and the number on the screen

Paper filters trap oils and fines. Metal filters pass more body. The same 30 g in 480 g water will taste different in a pour-over than in a French press. Adjust grind before you abandon 1:16.

Scale the water you actually pour, including rinse water you discard. If you rinse the paper and dump that water, do not count it in the 240 mL cups.

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Carafe marks versus 240 g cups

Many home carafes print 4, 6, 8, and 12 "cups" that are 4 to 6 ounces, not 240 mL. If you fill to the 8-cup line on a 5-ounce carafe scale, you have 40 fl oz, about 1,180 mL, which is 4.9 of this tool's cups, not 8.

Weigh the water you actually pour into the reservoir. Type that mass divided by 240 as the cups field, or convert ounces × 29.57 ÷ 240. Then apply the ratio.

A travel mug filled once is often 12 to 16 fl oz. That is 1.5 to 2 of this tool's cups. Two mugs at 1:16 is the default 30 g dose.

If you brew into a thermos for a soccer morning, brew the water you will drink plus a little for grounds absorption. Drip machines leave an ounce or two in the basket. The calculator does not subtract hold-up.

Hard-water scale on a drip machine lowers brew temperature over months. Descale on the maker's schedule. A perfect 1:16 ratio still tastes thin if the shower head dribbles at 180 °F.

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Fix grind and time before you abandon 1:16

Sour cups at 1:16 are often under-extracted: too coarse, too cold, or too fast. Bitter cups are often too fine or too long. Change one of those before you jump to 1:14 or 1:20.

A blade grinder makes dust and boulders. The dust extracts bitter while the boulders stay sour. Burr grinders are worth the money if you drink drip every day. The ratio cannot repair a mixed particle pile.

Paper-filter pourovers at 1:16 with a 3-minute contact time sit in the Golden Cup contact-time band for drip. If your kettle pour is done in 90 seconds, you under-extracted even if the grams were perfect.

French press at 1:16 wants a coarser grind and a 4 to 6 minute steep, then a gentle plunge. Pressing hard dumps silt. The coffee grams stay 30 g per 480 g water.

Work coffee for parents of infants is often the second pot. Stale grounds in the hopper pick up fridge smells. Weigh fresh beans for the second pot the same way you did at 6 a.m. The calculator does not know the beans sat ground overnight.

If you add a splash of milk for yourself, that splash is not extra brew water. Do not subtract it from the 240 g cups. Dose the coffee as if the cup were black, then add dairy.

Decaf uses the same mass ratio. Flavor is flatter. People then add syrup. Syrup is added sugar. Count it somewhere else.

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Limits

Espresso ratios (often 1:2 beverage to dry coffee) are not this calculator. Cold brew is a different page because time and temperature change the recipe.

Hard water and very soft water change extraction. SCA water standards exist for competition and equipment testing. Home tap water still makes a drinkable pot if the ratio and grind are sane.

A "cup" on a cheap drip carafe is often 5 ounces. If you treat those marks as 240 mL cups you will under-dose. Weigh once, write the real milliliters on the reservoir with a marker, and reuse that number.

This page will not tell a parent whether a 12-year-old should drink the pot. AAP caffeine guidance belongs next to the mug, not inside the ratio.

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How it works

Specialty Coffee Association brew charts cluster near 55 to 60 grams of coffee per liter of water, which is about 1:16 to 1:18.

Frequently asked questions

• Why not a caffeine calculator?

  Daily caffeine lives on HealthCalc. This page only sizes a pot.

Related calculators

References

1. SCA. Specialty Coffee Association
2. AAP HealthyChildren. Caffeine: a primer for parents
3. USDA. FoodData Central
4. Specialty Coffee Association. SCAA Golden Cup Standard (55 g/L ± 10%)
5. SCA. SCA coffee standards overview
6. FDA. Nutrition Facts label
7. FDA. Spilling the beans: how much caffeine is too much?
8. USDA Ask FSIS. 2 Hour Rule
9. USDA FSIS. Danger Zone (40 °F to 140 °F)