Direct Answer: In the universe of new-school specialty coffee, 18 grams is the standard dose for a double shot of espresso. Traditional Italian definitions (such as those established by the Istituto Nazionale Espresso Italian) also confirm coffee a double shot, approximately 14 grams, but this was set based on darker roasts and smaller equipment. Today you’d be hard pressed to walk into a third wave espresso shop or even go home and pull a shot with your fancy machine without seeing the default 18g – 20g as “standard” for a double shot. If you are using fresh beans and a commercial standard portafilter size (58mm) 18g is your starting point not less for one shot.
For The Beginner Home Barista: Getting To Know Your Gear
The Confusion: You read somewhere online that 18g is “normal,” but perhaps your machine’s manual says 14g, or maybe your coffee puck is looking a bit scatty.
The Truth: “The shot” is also – if not more so dependent on the metal filter basket in your group handle, not simply a weight of coffee.
The “Basket Capacity” Logic:
Not all machine is going to just be able to take 18 grams of coffee and you force it into the machine. Which basket are you currently in? Good consumer machines usually come with two baskets:
- The Single Basket: Sometimes conical or narrowing at the bottom. It holds 7–10g.
- The Double Basket: Is built with straight walls or slightly tapered and is much deeper. It can store between 14–18g (depending on the company).
Action Plan:
- Visual Inspection: Pull out your basket. If its the side walls are straight and deep then, it is a double basket. If it tapers suddenly, like a “V”, it is a single.
- The Roast Factor: Dark roast occupies more physical space than light roast an 18g dose of dark deep roasted coffee looks larger than a lighter roasted equivalent. If you’re using a dark and oily roast, the 18g amount might overflow a “double” basket (regular size).
- The 18g Rule: You want to start thinking of 18g as your fixed variable. Use the double basket, weigh 18g exactly and adjust your grind to get the liquid out in 25-30 sec. Do not attempt to dose 18g in the single basket, it will choke the machine.
For The Specialty Coffee Nerd: The “Golden Ratio” Shift
The Issue: How did we get from 14 ounces to 18 ounces, which is a completely different standard? Simply to sell more coffee?
Truth: The change to an 18g dose is based on the Brew Ratio of the lighter roasted, modern coffee.
The Theory:
- The classic Italian espresso is made with very dark roasts. Dark roasts are very soluble; with just 14g of coffee and a small amount of water, you can get lot of flavor and body.
- Specialty 3rd wave coffee is roasted lighter to retain fruit notes and acidity. Light roasts are less soluble. Bring the dose up (18g) for a light roast to allow the right texture and flavour intensity.
The 1:2 Ratio Protocol:
So don’t think, “Single vs Double” (or whatever number)” Think input/output ratios.
- Input: 18g of ground coffee.
- Ratio: 1:2 (The industry standard now).
- Output: 36g of liquid espresso.
Critical Insight:
If you pulled the old school 14g with a modern standard light roast, your espresso frequently turned out thin and watery because you have to grind so fine or it tastes bitter. 18g is the dose with enough resistance and soluble mass to generate a syrupy, balanced shot using modern beans.
For The Gear Upgrader: Precision Baskets and Headspace
The Confusion: You bought a “precision” basket (VST/IMS) marking it as being “18g”, yet your puck is soggy or the shower screen dents your coffee.
The Reality: An “18g basket” is a nominal rating, not a statute. It is the actual capacity that is determined by the physical density of the bean.
The Concept of Headspace:
Headspace is the space between the top of your tamped coffee puck and your machines shower screen. This space is essential for the water to collect and build up equal pressure.
- Too much coffee (Overdosing): The puck comes into contact with the screen before brewing. This results in channeling (cracks in the puck) as the water has nowhere to expand.
- Not enough coffee (Underdosing): Too much Head space results in “soupy” puck as after the shot finishes there is water sitting on top.
The “Coin Test” Technique:
To make sure 18g is right for your beans and new basket:
- Dose 18g into the basket, tamp as usual and put a small coin (1.5 – 2mm thick) on top of it.
- Insert the portafilter into the machine and lock it in place, immediately unlock it without brewing.
- Look at the puck.
- Coin in coffee: You took the overdose. Reduce to 17g or 17.5g.
- Coin is nowhere to be seen: You got enough brain space.
- Coin barely touched: This is ideal.
Why it matters: A VST 18g basket assumes a certain bean density. If you’re working with a dense, high-altitude Ethiopian bean, 18g of coffee may be too low. If you use a fluffy, darker roast, 18g might be on screen.
The Troubleshooter: Flow dynamics and resistance
The confusion: You’re pulling 18g because “that’s what people do,” but your shots are either gushing out in 10 seconds or drooling into the cup for a minute.
The Truth: Adjusting the dose (mass) has a bigger impact on backpressure than adjusting grind size.
The “Puck Resistance” Mechanism:
Consider the coffee puck like a dam that the water needs to break through.
- 18g Puck: Thick wall’s Thick walls. High resistance.
- 14g Puck: Less of a barrier. Low resistance.
The Diagnostics Flow:
If pulling an 18) and extractions are starting to be difficult:
- Don’t change the 18g yet. Hold the dose steady to take out a variable.
- Grind Adjustment: 18g shot takes 15 seconds (too fast): Grind finer. If it takes 50 seconds (too long), grind more course.
The Exception (Aka the 58mm Problem): If you are dosing less than 17g into a 58mm commercial portafilter (because you want to be patient with your coffee supply), then puck is too thin. 9 bars of pressure can cause even a thin puck to crack (channel). 18g is more forgiving to newbies, because the thicker puck is structurally more robust and that means less channeling.
TL;DR If your basket is 18g rated, fill it up with 18g +/- 1g of grounds (by weight) Try to do single-serve shot by pouring in just 10 grams and the extraction will battle against physics, you get sour, muddy coffee.
Frequently Asked Questions
Q: Are 18 grams a single or double shot of espresso?
A: In contemporary specialty coffee, the typical dose for a double shot is 18 grams. Where a double shot might have been defined as 14 grams for the traditional Italian machines, those of us with modern independent shops and high-quality home machines take 18g to 20g as a standard double in a 58mm basket.
Q: Yet another question to grind through: Why are we pulling “wetter” shots now than ever – 18g of dry coffee in 30g liquid out, which is bigger than the old standard of 14g in for 20-25g out?
A: Most of the change comes from having lighter roast profiles for the specialty coffee. Dark Solubles – Traditional dark roasts are very soluble and can give a heavy body without using much coffee (14g), however, modern ‘light’ roasted coffees are less soluble (requiring 18-20g to reach similar fullness of texture, levels of TDS and flavour balance).
Q: How can I recognize a single compared to a double basket visually?
A: Single baskets are typically more conical or tapered as a “V” shape and hold somewhere between 7-10g, while double baskets tend to have straighter or less tapered walls and be deeper with capacity ranging anywhere from 14-18g depending on the manufacturer.
Q: What’s the “Coin Test” and how does this help with dosing?
A: The coin test can be used to confirm that you have the correct headspace (the distance between your puck and the shower screen). To run it, put a small coin on top of your tamped puck and lock the portafilter into machine without brewing; if you see an impression of the coin in the coffee when taken out, then you’ve overdosed that basket and need to take off some coffee.
Q: Could I use a 14g dose in an 18g basket, saving me coffee?
A: No you should not underdose a basket that much. If you put 14g in an 18g basket, your result will be a too-thin puck that can’t hold-out against the espresso machine’s 9 bars of operating pressure (which causes channeling), resulting in a muddy and sour shot.
References
- Istituto Nazionale Espresso Italiano (INEI). (1998). Certified as the Italian Espresso and Cappuccino. This means the traditional legal definition of Italian Espresso is hereby put in place: “7 g ± 0.5 g of ground coffee” (per single shot, i.e., ~25 ml).
- Specialty Coffee Association (SCA). (2018). Espresso Protocol. While it is possible the SCA fails to set a single fixed mass, nonetheless contemporary competition standards and best practice guides are unanimous in utilising this ratio with input doses between 18g and 20g in double baskets.
- VST Labs. (2011). VST Precision Filter Basket use summary. In-depth breakdown of how basket hole surface area and geometry needs different doses to hit optimum Total Dissolved Solids (TDS) and extraction yields (+/- 1g in rating).
- Rao, S. (2017). The Non-Fiction of Coffee. Explains how roast profiles have changed over time and why lower solubility requires more coffee to be used than traditional dark roasts (18g+).
