Chemex coffee ratio calculator

It defines one Chemex cup as 150 millilitres and applies a fixed 1:16 coffee-to-water ratio, so the result is consistent every time. Enter the number of cups you plan to brew and receive the required coffee in grams and water in millilitres. The calculation is deterministic, quick, and useful for scaling the same balanced recipe up or down without mental arithmetic.

Understand the fixed Chemex recipe

This calculator uses one clear recipe: one part ground coffee for every sixteen parts water by mass. Because a millilitre of brewing water is approximately one gram for recipe planning, 150 millilitres per cup can be divided directly by sixteen to find the coffee dose. That gives 9.375 grams of coffee for one defined cup, with the displayed grounds rounded to two decimal places. The fixed ratio removes uncertainty when you only need a dependable baseline. It does not claim that every bean, grinder, or taste preference must use exactly the same recipe. Instead, it provides a repeatable reference that makes comparisons meaningful. If a six-cup brew tastes too strong or too light, you know the starting quantities and can adjust grind size or later change your personal recipe deliberately. The returned ratio is always shown as 1:16, while water is reported in millilitres and coffee in grams, the practical units most brewers and kitchen scales support.

Enter cups and measure the result

Enter a positive whole number for the cup count. In this calculator, a cup is a recipe unit of 150 millilitres, not a large household mug and not necessarily the numbered mark printed on every brewer. The tool multiplies your count by 150 to determine total water, then divides that water amount by sixteen to determine the grounds. For the most repeatable brew, place the Chemex on a scale, tare it, weigh the calculated coffee, and then pour until the scale reaches the returned water amount in grams. The millilitre result can also guide a measured kettle, although weighing water is usually easier during a pour-over. Remember that the finished drink will weigh less than the water you poured because the grounds retain some liquid. The output describes the brewing input, not the final beverage volume. Use fresh coffee, an appropriate filter, and an even pour while keeping the calculator’s quantities unchanged when comparing technique from one brew to the next.

Scale a brew without changing its balance

Scaling both ingredients together preserves the intended strength far better than guessing an extra scoop when more people arrive. Choose the total cup count before brewing, calculate once, and use the resulting numbers as the recipe for the entire batch. A larger batch may require a slower or more carefully controlled pour because the coffee bed is deeper, but the ingredient relationship remains the same. If the calculated water exceeds the comfortable working capacity of your Chemex, split the recipe into two equal brews rather than filling above a safe level. The function is deterministic: identical input always produces identical output, and it uses no network request, random value, or current date. That makes it suitable for a kitchen page, a café prep sheet, or an automated recipe workflow through the API at $0.002 per request. Non-positive counts are rejected instead of producing meaningless negative or empty recipes. This explicit error behaviour helps integrations distinguish an invalid order quantity from a legitimate brewing result.