Coffee Brewing Ratio Calculator

What is the coffee-to-water ratio?

The coffee-to-water ratio is the amount of dry coffee grounds (in grams) relative to the amount of water (in grams or milliliters — they're equivalent for water). A ratio of 1:18 means 1 gram of coffee for every 18 grams of water. For a typical 8 oz cup (240 ml of water), that's about 13 g of coffee.

The ratio is the single biggest factor in determining how strong your coffee tastes — more so than roast level, bean origin, or grind size. Get the ratio right and almost any brew method will taste good; get it wrong and even the best beans will taste bitter (too strong) or watery (too weak).

The SCA golden ratio: 1:18

The Specialty Coffee Association (SCA) recommends a brewing ratio of 1:18 — that's roughly 55 g of coffee per liter of water. This produces a balanced cup with a Total Dissolved Solids (TDS) of about 1.15–1.45%, which sensory research has identified as the range most coffee drinkers find pleasant.

Note: the SCA golden ratio assumes drip / pour-over brewing. Other methods use different ratios because they extract differently:

• Drip / pour-over: 1:17 to 1:18 (balanced)
• French press: 1:15 (stronger, fuller body)
• AeroPress: 1:14 to 1:16 (versatile)
• Cold brew concentrate: 1:8 (then dilute with water or milk)
• Espresso: 1:2 (concentrated shot, brewed under pressure)
• Moka pot: 1:10 to 1:12 (stovetop, between drip and espresso)

How caffeine extraction works

Caffeine makes up about 1.2% of Arabica coffee beans by mass and 2.2% of Robusta beans. When you brew coffee, hot water extracts roughly 90% of the available caffeine in the grounds (the rest stays trapped in the puck).

So a 15 g serving of Arabica coffee (15 × 12 mg = 180 mg available caffeine) typically yields about 160 mg of caffeine in the cup. The same weight of Robusta (15 × 22 = 330 mg available) yields about 300 mg — nearly twice as much. This is why some espresso blends (which often include Robusta for crema) feel noticeably stronger than 100% Arabica drip.

Common brewing mistakes

• Using volume instead of weight: A "tablespoon of coffee" can vary from 5 to 10 g depending on grind and how densely it's packed. Use a kitchen scale.
• Water too hot or too cold: 195–205°F (90–96°C) is ideal. Boiling water burns the grounds; cooler water under-extracts.
• Wrong grind size: Espresso needs fine, drip needs medium, French press needs coarse. Wrong grind = wrong extraction time.
• Not weighing the water: Coffee makers' "cups" are often 5 oz, not 8 oz. Measure water in ml.
• Stale beans: Coffee peaks 2–30 days after roasting. Old beans taste flat regardless of ratio.