Chemex Coffee Ratio Calculator
Find the ideal Chemex coffee to water ratio. Adjust for cup size, brew strength, and roast level.
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How to Use This Calculator
- Set your cup count — how many 8 oz cups you want to brew.
- Choose your strength — weak for a lighter brew, strong for a more concentrated cup.
- Adjust roast level — darker roasts extract faster and need less coffee, cooler water, and a finer grind.
The calculator adjusts all six parameters in real time: water volume, coffee weight, water temperature, grind size, brew ratio, and brew time.
Understanding the Ratios
The brew ratio is the relationship between coffee and water by weight. A 1:15 ratio means 1 gram of coffee for every 15 grams of water — stronger and more concentrated. A 1:17 ratio produces a lighter, more delicate cup.
Light roasts benefit from slightly stronger ratios (1:14 to 1:16) because they're denser and harder to extract. Dark roasts are more soluble, so a weaker ratio (1:16 to 1:18) prevents over-extraction and bitterness.
Chemex Brewing Tips
- Always use a gooseneck kettle for controlled, even pouring.
- Rinse the Chemex filter with hot water before brewing to remove paper taste and preheat the vessel.
- Start with a bloom — pour just enough water to saturate the grounds (about 2x the coffee weight) and wait 30–45 seconds.
- Pour in slow, concentric circles, keeping the water level consistent.
- Use a burr grinder for consistent particle size. Blade grinders produce uneven grounds that lead to both over- and under-extraction.