When you picture one cup of coffee, what is the actual image in your head? Is it a line on a coffee maker, a standard diner mug, a small disposable paper cup, a big ol’ Venti, something even larger?

As our friend Meister has pointed out, when it comes to coffee “cup” can mean a surprisingly large amount of things. And whether you’re looking to find the right size coffee maker for you, trying to figure out a consistent brew recipe for the one you already have, or even figuring out how often to order coffee (or have it automatically shipped to you), it’ll be very helpful to figure out what it means to you.

If you’re cooking or baking, and you’re in the US, the definition of a cup is pretty simple: it’s exactly eight ounces. You might have a little metal or plastic cup with a handle attached to your teaspoon measures, for example, and if you fill it up with flour or water, you’re likely to hit pretty close to the eight ounce mark.

For some people, and for some coffee shops, eight ounces is a totally normal amount of coffee to consume at once. But when we say “cup of coffee” we most often don’t mean a specific measurement. The most basic diner mug in my house comes in at just under ten ounces. The coffee shop I used to work at in Midtown Manhattan served a “small” as 12 ounces. So when a home coffee maker says it brews four to ten cups, for example, what does that mean? 32 to 80 ounces? Four to ten diner mugs?

Well, it means neither of those things. I tried to carefully measure out a cup in my Bonavita drip brewer and found that it averaged out to a little over five ounces. A few coworkers did similarly with their Technivorm Moccamasters and got pretty close to four ounces. According to the capacities on Chemex’s website, they’re counting a cup as five ounces on the dot. On my beloved Kalita Wave decanter, a cup is around four and a half ounces.

If you want to dial in your brew recipes and make consistently delicious coffee — despite these challenges — you have a few options. You could, of course, just weigh your water before every brew and know exactly how much you’re putting in. And if you want to do that, I definitely wouldn’t discourage you; measuring by weight will always get you the most consistent results. But part of the joy of owning an auto drip machine, I think, is convenience, so here’s the easiest way to figure out how much water is actually in one of your machine’s cups.

• Pour more water than you think you’ll need to fill to the lowest line on your brewer into a vessel that’s easy to pour from (maybe your brewer’s carafe? maybe a large jar?)
• Put the full vessel on a scale and tare to zero
• Slowly pour the water into your brewer until you hit as close to the lowest cup line as you can
• Put the vessel back onto the scale
• The absolute value of the number on the scale (that’s a fancy way of saying take off the “-” sign) is the amount of water you’ve poured
• Divide that number by the amount of cups at the line you poured to, and there’s your cup to ounce (or gram if you’re on that metric like me!) conversion

From there, figure out what line you usually brew coffee from, multiply your ounce/cup measurement, and multiply that 1.75, and there’s your dose of coffee (in grams). Enjoy, and never have to think about what the word “cup” means again.