For a 1:16 brew with 500 g water, divide 500 by 16: use 31.25 g coffee. For a 1:15 brew with the same water, 500 ÷ 15 = 33.33 g coffee. The second recipe contains 2.08 g more dry coffee for the same water. If a scale reads in whole grams, use 31 g or 33 g, then record the choice so a later adjustment has a clear starting point.
Worked example with numbers
Put the brewer and vessel on a scale, tare, add the coffee mass, then add the target water mass. Water in grams is convenient because 1 mL of water is approximately 1 g at kitchen accuracy, but use the scale reading rather than estimating from a mug. The coffee ratio calculator calculates either missing mass when the other mass and ratio are known.
How to make the calculation
Ratio controls the dose relative to brew water, while grind, contact time, water temperature, filtration, and agitation affect extraction. A stronger-tasting cup is not automatically caused by a lower ratio: fine grinding can overextract, and a coarse grind can underextract even at the same ratio. Change one variable at a time. For example, repeat 30 g coffee and 480 g water before deciding whether the next change should be 1:15 or a different grind.
Check the units and assumptions
Do not read 1:16 as 16 g coffee plus 1 g water; the convention is coffee to water. Do not substitute four household “cups” for a stated water mass without naming the cup size. Do not confuse 500 g brew water with 500 g beverage in the cup: coffee grounds retain water and some water remains in the brewer. A scoop changes mass with bean size and grind, so it cannot define a reproducible ratio.
Common mistakes
A ratio is a starting formula, not a universal quality grade. Espresso, immersion, pour-over, and batch brewing use different equipment and recipes. A ratio cannot diagnose stale coffee, mineral composition, grinder inconsistency, or a blocked filter. Keep caffeine, dietary, and medical questions separate from brew arithmetic; this page only explains the mass relationship used to prepare a drink.
When this result does not apply
The Specialty Coffee Association’s Certified Home Brewer requirements specify a starting coffee-to-water ratio of 55 g per 1 L, with adjustment for grind. Its published requirements are a named reference for using a measurable mass ratio rather than an undefined scoop.
Source for the external fact
Enter your chosen masses in the coffee ratio calculator, convert a recipe’s liquid units using the volume converter, and use the ingredient ratio tool for non-coffee proportions.
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