For a standard 58mm double basket, 18 grams in, about 36 grams of liquid espresso out, in roughly 25 to 30 seconds. That is the working answer and it is where to start. But the dose is a property of your basket, and baskets are sold in different capacities: a 54mm Breville double is commonly rated around 16–19g, and many 51mm De’Longhi baskets are rated around 14–16g. If you dose 18g into a basket rated for 15g, the puck hits the shower screen, the shot channels, and no amount of grind adjustment will rescue it. So: find your basket’s rated capacity, dose inside it, and use the ratio below.
There is a second reason the single number misleads. A “double shot” names the basket you are using, not a fixed volume of drink. A double basket paired with a short, concentrated pull and the same basket paired with a long one are both doubles, and they are very different drinks.
Find your basket’s capacity first
Three ways, in order of reliability.
1. Read the basket.Many baskets are stamped with their dose on the rim or the underside, often as a range like “18–20g”. If yours is, that is the answer and you can stop.
2. Check the manual or the manufacturer’s page for your machine, which usually states the dose for the baskets supplied in the box. This is the number we would trust over any general guidance, including ours.
3. Measure the headroom. Dose what you think is right, tamp level, lock the portafilter into the group, then unlock it and look at the puck. A clean puck surface with a shallow, even impression from the shower screen means you have roughly the right amount of room. A deep screw imprint pressed into the puck, or grounds smeared up the basket walls, means you are over-dosed. Nothing touching the puck at all and a swampy surface afterwards suggests you are under-dosed for that basket.
Typical rated ranges by basket size, as a sanity check rather than a specification — always use the figure published for your own basket:
58mm commercial double:commonly 18–20g. The size most published espresso advice assumes.
54mm (Breville) double:commonly around 16–19g.
51mm (many De’Longhi) double:commonly around 14–16g — covered in detail in espresso dose for a 51mm portafilter, which is the page to read if that is your machine.
Single basketsare usually half the double, in the 7–10g region, and are genuinely harder to pull well because the shallow puck bed is less forgiving.
The dose is half the recipe — the ratio is the other half
A dose on its own tells you nothing about the drink. What makes it a recipe is the brew ratio: the weight of liquid espresso you let out, divided by the weight of dry coffee you put in.
1:2 is the standard. 18g in, 36g out. This is the default for a modern espresso and the number to learn first.
1:1.5 is a ristretto— 18g in, 27g out. Shorter, thicker, sweeter, less of everything that comes out late in a shot. Often flattering to dark roasts.
1:3 or longer is a lungo— 18g in, 54g+ out. Thinner and more developed, which can suit a light roast and can also drag out bitterness. Ristretto vs lungo covers the trade properly.
Three things about measuring this that trip people up. Weigh the output, do not eyeball it— crema makes volume useless as a guide, since the same 36g of liquid can fill wildly different amounts of cup depending on the bean. Time is a diagnostic, not a target: 25 to 30 seconds is what a correct shot usually takes, so if you hit your ratio in 15 seconds the grind is too coarse, and if it takes 45 the grind is too fine. You adjust grind to land the ratio in the time window; you do not adjust the ratio to hit a time. And start the timer when you start the pump, consistently, so your numbers mean the same thing every day.
Why the basket decides, in one paragraph of mechanism
Espresso works by forcing water at around 9 bar through a compacted bed of coffee. For that to extract evenly, the water has to meet the whole bed at once — which requires a small, consistent gap between the tamped puck and the shower screen, and a puck deep enough to offer uniform resistance. Over-dose and the puck swells into the screen, loses that gap and gets disturbed, so water finds the path of least resistance and channels through one spot. Under-dose and the bed is too shallow and loose to resist evenly, and water races through. Both produce the same symptom — a fast, pale, sour, thin shot — from opposite causes, which is exactly why guessing the dose makes dialling in feel impossible.
A starting recipe you can actually run tomorrow
1.Find your basket’s rated dose. Use the middle of the range.
2.Weigh the dry coffee to 0.1g. Every time — a scoop will not do this.
3. Distribute and tamp level. An uneven puck wastes a correct dose.
4. Pull to double the dose in liquid weight, timing from the pump.
5. If it ran faster than ~25s, grind finer. Slower than ~30s, grind coarser. Change one thing at a time and keep the dose fixed while you do.
That loop needs exactly one tool you may not own: a scale that reads to 0.1g and fits where you brew. The three picks below are the dose, grind and tamp ends of making a weighed dose actually repeatable — the scale is the one that matters most and costs least.
Why 18g became the default number
It is not a law of physics. The 58mm group is the commercial standard, the double baskets supplied with those groups are typically rated 18–20g, and a very large share of published espresso advice is written by and for people using them. So “18g” really means “the middle of a standard 58mm double basket”. It is a good number if that is your basket and a misleading one if it is not — which is most home machines, since Breville’s 54mm platform and De’Longhi’s 51mm platform together account for a very large part of the home market.
Single, double, triple
These name baskets, not volumes. A singleis roughly half a double, around 7–10g in a 58mm, and is harder rather than easier — a shallow bed is less forgiving of an uneven tamp. A triple at 21g or more needs more headroom than some machines have and more steady pressure than many pumps deliver. If you want a bigger drink, the right move is almost always a double pulled to the same ratio with more water added afterwards, which is an americano, rather than a bigger basket.
Pressurized baskets change the answer
If your machine came with a pressurized(dual-wall) basket — common on entry machines, including most De’Longhi and many budget units — it manufactures crema through a valve rather than through resistance from the coffee bed. Dose and grind matter much less, because the basket, not the puck, is controlling the flow. Use whatever dose fills it level, and know that precision will not buy you much until you move to a single-wall basket. The mechanism is in pressurized vs non-pressurized portafilters.
When the dose is right and the shot still is not
Once the dose is weighed and inside the basket’s range, dose stops being the suspect. In rough order of likelihood: grind (the main lever, and the one to move first), distribution (clumps and an uneven bed cause channeling at any dose), bean freshness (very fresh coffee gushes as it degasses, very stale coffee runs fast and tastes flat), and temperature. The taste-based diagnosis is in why is my espresso sour or bitter, the full procedure in how to pull an espresso shot, and the crema-specific version in why does my espresso have no crema. For brewed coffee rather than espresso, the equivalent numbers are in coffee to water ratio.
