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It seems like a fairly basic question, but there's probably some more science to this. For an automatic-drip coffee machine, how much ground coffee should be used per unit water?

Various sources say that the "industry standard" is 7g (~1 rounded Tbsp) per "cup" (150-175mL, or 5-6 fl.oz.). Is this uniform for any (reasonable) amount of coffee (say, 200mL-4L / 1 cup to 16 cups)? Or would I want, say, a higher ratio of grounds-to-coffee for making 2 cups, than for making 12 cups? I feel like I, personally, tend to use more coffee (per unit water) when making fewer cups (I'm not sure why; shorter extraction time? Matters of water retention? Mere personal preference?).

Surely this also depends on total extraction time and grind level, but perhaps that is a separate question. With due credit, this question was partly spurred from this recent question.

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    The fraction of water held by the grounds should be constant if the amount of grounds varies proportionally with the water. However, since the filter also holds water, your statement becomes true for smaller pot sizes. Assuming that you are using a paper filter.
    – Suspended User
    Jun 3, 2015 at 17:25
  • @ChrisinAK -- Good point on the water retention for beans; I wasn't thinking about it correctly. Modified slightly; thanks!
    – hoc_age
    Jun 5, 2015 at 1:42
  • The industry standard from coffee producers and drinkers is 16:1. For some reason, many drip coffee maker manufacturers use a standard like you describe, which is about 25:1. Not clear why, but that ratio makes pretty weak coffee. 2 level tbsp per 6 oz cup is a lot closer.
    – fixer1234
    Jul 2, 2022 at 20:51

2 Answers 2

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I think you have already listed the "industry standard" that is the answer to your question. It is a good starting point for anyone and the amount can be adjusted by taste afterwards (more grounds for stronger coffee, less for weaker).

The amount may vary with brewing method of course, since depending on the method, brew components (grounds, filter, other components) may retain various levels of water.

The one add on I will stipulate is that it is always better (for groups) to brew coffee that is too strong. It is very easy to add some hot water to a cup and weaken a cup of coffee, however, if you like strong coffee and it's been brewed weak, you are just out of luck.

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  • Should one use the same ratio of coffee-to-water for any (reasonable) amount of coffee to brew? With an auto-drip machine, the machine will drip for longer when making 10 cups than making 5 cups; does this difference in extraction time matter for coffee-to-water ratio? E.g., use somewhat more (or less) grounds, or somewhat coarser (or finer) grind? Am I splitting hairs or asking another question?
    – hoc_age
    Jun 5, 2015 at 1:48
  • Maybe splitting hairs? Since the water is basically dripping through the grounds, the extraction time (excepting the first bit of water that soaks the grounds and stays) should be relatively the same for any given bit of water. Meaning the last bit water through the grounds should spend roughly the same amount of time in the grounds as the first bit that passed through and is already in the pot. The overall time spent extracting is greater, but the extraction time for any sub portion should be the same as a sub portion of a different sized pot.
    – Suspended User
    Jun 5, 2015 at 2:32
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Starbucks' standard is 2 tbsp. per 6 oz. cup. You may be able to adjust downward if your machine has a bypass which adds hot water straight to the pot.

The thing to pay attention to is overextraction. That poor quality gas-station coffee kind of taste. If you're getting that, you need to add more grounds. If the result is too strong, dilute it with hot water.

I should add that this is also the Maxwell House standard proportions established many decades ago. See also: https://coffeefaq.com/site/node/95 .

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