A single espresso is about 1 oz (30 ml) in the cup. A double— which is what almost every machine and cafe actually pulls, and what you get when you order "an espresso" in most of the US — is about 2 oz (60 ml). A ristretto is a restricted double at roughly 1 to 1.5 oz, and a lungo is a long one at about 3 oz. Those are the numbers people are looking for, and they are useful as a rough guide.
Here is the complication, and it is the reason this page is longer than four numbers: volume is a bad way to measure espresso.A shot is part liquid and part crema, and crema is foam — its volume depends on how fresh your beans are, how much Robusta is in the blend, and how hard your machine pushes. Two shots of identical strength can read 1.5 oz and 2.5 oz in a glass purely because one bean produced more foam. That is why cafes stopped measuring shots by volume and started weighing them.
The number baristas use: the brew ratio
Modern espresso is specified as a ratio of dry coffee in to liquid espresso out, by weight. The standard starting point is 1:2— so a typical double is around 18 g of coffee in, 36 g of espresso out, pulled in roughly 25 to 30 seconds.
Grams of espresso rather than millilitres, because weight is not affected by foam. Thirty-six grams out is thirty-six grams out whether the crema is thick or thin, which makes it a recipe you can repeat tomorrow. This is the single biggest reason a scale with a timeris the most valuable cheap accessory in espresso — it converts "about two ounces" into a number you can hit again.
The ratios in common use, all by weight:
Ristretto, 1:1 to 1:1.5— 18 g in, 18 to 27 g out. Shorter, thicker, sweeter, less of the harsher compounds that come out late in an extraction. Excellent in milk. Normale, 1:2 — the default, and the one to learn first. Lungo, 1:3 to 1:4— 18 g in, 54 to 72 g out. More volume, more caffeine extracted, and more bitterness, because you are pulling water through grounds that have already given up the good part. Ristretto vs lungo vs espresso goes deeper on how each one tastes.
Why your machine's "single" button is misleading
Most home machines ship with 54mm or 58mm double baskets and a preset single and double button that controls volume of water pushed, not the ratio. Three things follow from that. A "single" on a double basket under-doses the basket and pulls a thin, fast shot. A preset double is calibrated for whatever dose the factory assumed, not yours. And the preset knows nothing about your grind, so the same button produces a different drink when you change beans.
The fix is not a different machine, it is weighing. Dose the basket to its rated weight — most home double baskets are 18 g, some Breville baskets are rated 18 to 22 g — put the cup on a scale, and stop the shot at your target yield rather than when the machine decides. How to dial in espresso is the full procedure.
Shot size in the drinks you actually order
Almost no one drinks espresso neat every day, so the practical question is how many shots go in each drink. A cortado or flat whiteis a double in a small amount of milk — around 4 to 6 oz total — which is why they taste most strongly of coffee. A cappuccino is a double in about 6 oz. A latte is a double in 8 to 12 oz, and at 16 oz you want two doubles or it will taste like warm milk. An americano is a double with hot water added, usually 6 to 8 oz total. Espresso drinks explained has the whole menu, and latte vs cappuccino vs flat white covers the three people confuse most.
What to buy, if anything
You do not need equipment to understand this page. If you want to measure properly, a 0.1 g scale with a timeris the purchase that matters — weight and time are the two numbers that turn espresso from guesswork into a recipe. Marked shot glassesare a cheap, genuinely useful visual while you are learning, because clear glass also shows the shot's color and tiger-striping, which tells you something about extraction; just know that a scale beats them for accuracy. Proper espresso cupsare a real functional item rather than a nicety — thick porcelain at around 3 oz holds heat so a small shot does not go lukewarm, which oversized mugs cannot do.
Ounces, millilitres and grams, side by side
For liquid espresso the three units are close enough to convert casually: 1 fl oz is about 30 ml, and a millilitre of espresso weighs very slightly more than a gram (it is denser than water because of the dissolved solids), so 30 ml is roughly 30 gfor everyday purposes. That is why 36 g out and "a bit over an ounce and a quarter" describe the same shot.
Where the units stop agreeing is the crema. A freshly roasted, Robusta-containing blend can add half an ounce of foam to the top of a shot, and foam weighs almost nothing. So the glass says 2.5 oz, the scale says 36 g, and the scale is the one telling you about the coffee. If you have ever wondered why your shots look different day to day while tasting the same, that is the answer — what is crema explains what the foam is made of.
The Italian definition, for context
Espresso's traditional Italian specification is a 7 g single pulled to about 25 to 30 ml in 25 to 30 seconds at around 9 bar of pressure. Most of the world, including the US, now works in doubles, with 14 to 18 g doses depending on the basket, and modern specialty baskets are built around 18 g. Both are legitimate; the Italian numbers simply predate double baskets being the default.
How to use volume if you have no scale
It is workable, with two habits. First, judge the liquid, not the foam— let the shot settle for ten seconds and read the dark liquid level rather than the crema line. Second, watch the time: a double that takes 25 to 30 seconds to reach about 2 oz is in the right ballpark, and if it hits 2 oz in 12 seconds your grind is too coarse, while 50 seconds means it is too fine. Time plus settled volume gets you most of the way there, which is how everyone did it before cheap scales existed.
When to change your shot size on purpose
Shortening the ratio toward ristretto is the first thing to try if your espresso tastes bitter or harsh— you are stopping before the late, harsher compounds arrive. Lengthening it toward 1:2.5 is worth trying if your shots taste thin and sour, since under-extraction often needs more water through the bed, not less. But check grind first in both cases: sour vs bitter espresso explains which symptom points at which cause, and espresso grind size covers the dial that does the most work.
Caffeine, since it always comes up
A single espresso contains roughly 60 to 75 mg of caffeine and a double roughly 120 to 150 mg, varying with the bean and the roast. A lungo extracts somewhat more caffeine than a normale from the same dose because more water passes through the grounds; a ristretto somewhat less. Per ounce espresso is far more caffeinated than drip coffee, but a mug of drip is many ounces, so a large drip coffee usually wins on total caffeine — how much caffeine is in espresso has the full comparison.
