The bag of coffee I am using instructs to "Add 2 1/2 tablespoons (37 ml)" of ground coffee. When I measure out 2 1/2 tablespoons onto my food scale, it only comes out to about 13 ml.

Why does my 2 1/2 tablespoon measurement not equal 37 ml?

  • Are you using actual tablespoon measuring spoons? And what do you mean by food scale? Usually that means something that measures weight, not volume. – Cascabel Feb 25 '17 at 17:36
  • @Jefromi Yes I am using actual measuring spoons.And I am using a food scale that measures weight. – ScottK Feb 25 '17 at 17:38
  • 2
    Okay, so do you mean the scale says 13 grams, not 13 mL? – Cascabel Feb 25 '17 at 17:40
  • @Jefromi Well, it is a digital kitchen scale ("Ozeri kitchen scale" from amazon) for measuring by weight, but it has a mL option (along with g and oz). – ScottK Feb 25 '17 at 17:45
  • @Jefromi I just measured again and the scale will show 13 grams and 13 ml for the same measurement. – ScottK Feb 25 '17 at 17:47
up vote 9 down vote accepted

Your scale is measuring weight, not volume.

Some scales do have an option to "convert" to volume, but they have to do so based on density; they don't actually know what's on top of them. So unless yours is really fancy, and has a bunch of densities programmed into it, so that you can say "this is flour" and let it convert, it's probably just assuming everything is water, with a density of 1g/mL.

And this should be really easy to confirm. Just toggle it from weight to volume. If it says 13mL is 13g, then that's what it's doing.

So then it's telling you that your 2.5 tablespoons of coffee is 13g, not 13mL, because it's around 1/3 as dense as water.

  • So this is not an accurate way to measure dry ingredient mL (volume). Is it safe to assume that the ml can measure all liquid ingredients volume accurately? – ScottK Feb 25 '17 at 17:52
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    Depends how much accuracy you need. It'll work for anything that's basically water, for sure, e.g. milk. Cream is only a few percent off. But a lot of things are farther off. Oil and alcohol are less dense than water, e.g. vegetable oil is .93g/mL, and vodka is .92g/mL. Water with enough stuff dissolved in it is denser, e.g. a lot of sweet liqueurs are around 1.1g/mL, and honey is 1.4g/mL. If you're unsure, you should probably just google the density of whatever you're trying to measure. – Cascabel Feb 25 '17 at 17:56

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