A common phrase coffee brewers search for on the internet is “How much coffee do I use to make a cup of coffee?”I think a better question would be "How much water do I use to make a cup of coffee?"Here’s the reason why I say that.The first few times I made pour over coffees my cup ended up only three-quarters full.I thought I did everything right.I figured out how much water my cup held and calculated how much coffee I needed to grind for that volume of water. Yet when I added the water to the brewer I ended up with a short cup of coffee.Even though I was adding the perfect ratio of water to the mass of coffee grounds, not all of that water was making it into the cup.Finally, it dawned on me that the coffee grounds are absorb water. So the new question became, how much water do coffee grounds absorb.Once I figure out how much water the grounds are absorbing, I can determine what the final weight of my brewing set-up will need to be to brew a perfect cup of coffee. Like any nerdy scientist, I collected data and will present them below.I’ve also made a handy downloadable chart that will show you how much extra water you need to add to your brewer to make up for the water absorbed by the coffee grounds.How Much Coffee Depends on the Brewing ProcedureThe data below are for those coffee brewers that put the cup and pour-over brewer on the scale as one system similar to the setup shown below.If your pour over brewer is on a free-standing platform and the only thing on the scale is the carafe, then these data won’t pertain to you.Here's a post showing how I make my pour over coffee.You Need More Water than the Ratio SuggestsThe question of how much ground coffee you need depends on how much coffee your favorite cup holds.The mass of water is the determining factor, not the coffee.If you’re like me, I make pour-over coffee one cup at a time.I do the following to figure out how much coffee and water I need.Put the cup I’m going to use on the scale and zero out the weight.Pour water into the cup to the level I want.Note the weight of the water.Divide that weight by the water ratio I want to use for that cup of coffee and that is the weight of coffee beans I want to grind.Real ExampleThe cup pictured above is sold as a 12-ounce cup. But that doesn’t matter because I’m not sure where the 12-ounce level is in the cup.So to figure out how much water I need, I put it on a scale and zero out the weight.Next, I pour water into the cup to the level at which it is full, but not so high that it would spill it when drinking from it.It held 366-grams of water. By the way, 12-ounces is about 340-grams, so never go by the stated volume.I want to brew my coffee at a 16: 1 water to coffee ratio.So, 366-grams of water ÷ 16 = 22.875-grams of ground coffee beans.Write down these numbers somewhere (I use a chalkboard to record my different cup volume-weights) that way you won’t have to go through the measurement again.The DilemmaIn reality, if you add 366-grams of water to a pour-over brewer your cup of coffee won’t be full.The coffee grounds absorb water and stop it from reaching your cup. So the coffee in the cup has a much smaller ratio than you planned, making the coffee stronger than expected.For this reason, many people don’t use a scale, they add water to a known mass of coffee grounds until their cup is full or the coffee level in their carafe is at a known volume and then pull that container out from under the brewer.Then they place another container under the brewer and allow the remaining water to drain before discarding.Both methods work, but I would rather add the correct amount of water and let it drain while I do something else, coming back for the cup in a couple of minutes.To figure out how much extra water I need, I collected data by the method described below. ProcedureI made an assumption that the ground coffee absorbed the same amount of water per gram each time I brewed a cup of coffee. I brewed 10 cups of coffee and kept track of the following parameters. All weights are in grams.Dry weight of coffee used.Weight of Hario V60 with pre-wet filter and dry ground coffee.Weight of Hario V60 after brewing coffee including wet ground coffee after draining,Using those data, I calculated the following:Difference between Hario V60 & coffee wet and the Hario V60 & coffee dry.Weight of absorbed water.Percentage difference in weight between wet & dry coffee.ResultsI varied the weight of coffee in the beginning but then saw that the coffee grounds were absorbing about the same amount of water per gram, so in the end, I used the same mass of coffee beans.The coffee grounds absorbed 1.27-times its weight in water.No wonder my coffee cups weren't full when I first started brewing pour overs.Below is the data (you can click the image to make it expand):Back to the ExampleUsing the same coffee cup as in the first example, the data shows that I need to add extra water to the brewer equal to 1.27-times the weight of dry coffee.My cup that holds 366-grams of water, and using 22.9-grams of dry coffee I need to add an extra 29.1-grams of water for a total weight of 395.1 grams of water to fill the cup to the level I want.366-grams+ (22.9-grams * 1.27) = 395.1-gramsNow the brewed coffee in my cup is at a 16:1 water to coffee ratio.Free DownloadI’ve created a free downloadable chart for you that has calculated how much extra water you should for a range of dry coffee weights.When you want to know how much extra water you need to add to your pour-over, consult the chart to find the weight of dry coffee you use and to the right will be the how much extra water (by weight) you need to add due to the coffee grounds absorbing water during brewing.Click the button below and you’ll be able to download the chart. Click to Get the Chart Just as important as how much coffee you need is how much water you add to make up for absorption.I don’t remember seeing this tip in any other pour-over coffee guide.I think it’s an important point to bring up to people that haven’t brewed pour over coffee before.It could make the difference between them liking the taste of pour over coffee or not.The taste of coffee in a short pour cup is much stronger than a full one since the last coffee coming out of a brewer will be weaker than the first two-thirds of the pour.I want more people to brew better-tasting coffee, and it’s little tips like this that will make a difference.Hopefully, this post has helped you if you’re new to pour over coffee brewing. If you’re not so new to pour overs, I’m sure the downloadable chart will make it easier for you when brewing your next pour over coffee.