A coffee bag works like a teabag. Ground coffee sits inside a filter mesh, you pour on hot water, leave it three to four minutes, give it a stir, then lift the bag out. No machine, no grinder, no filter paper, and nothing to wash up but the mug.
That is the whole mechanism. What decides whether the cup is any good is not the format. It is how much coffee somebody put in the bag, and we will come back to that number more than once.
What is inside a coffee bag, and how it brews
Inside is ground coffee. That is all. Ours holds 12g of 100% Arabica in a pyramid of plant-based mesh made from GMO-free corn starch rather than oil-based plastic. Hot water soaks through the mesh, pulls flavour and oils out of the grounds, and the mesh holds back every last bit of grit. It is immersion brewing, the same principle as a cafetière, without the cafetière.
The pyramid shape is doing a job, not looking pretty. Wet grounds swell and shift as they take on water, so the bag needs headroom for the coffee to bloom. Flat sachets pin the grounds together and the water only ever meets the outside of the clump.
Then there is the dose, which is where most coffee bags quietly give up. A lot of them run around 7.5g. We pack 12g, which is roughly 50% more coffee for the same mug of water. The problem with coffee bags was never that it is a bad idea, it is that the idea kept being done badly.
When you are finished, the bag goes in your food waste bin and composts along with the grounds, and the cardboard box goes in the paper recycling.
How to brew a coffee bag properly
Four minutes, one stir, one squeeze. In order:
- Drop the bag in your mug.
- Add freshly boiled water, off the boil by twenty seconds or so. Around 220ml fills a standard UK mug and suits a 12g bag.
- Press the bag against the side of the mug with a spoon. This first squeeze pushes water into the grounds and starts the extraction properly.
- Leave it three to four minutes. Three for a lighter cup, four for a fuller one.
- Squeeze again, lift it out, add milk if you take it.
Leaving the bag in indefinitely will not ruin the cup the way an over-steeped cafetière does, though it does keep creeping darker. If you like it strong, take the four minutes rather than the ten.
Are coffee bags any good?
Yes, if the dose is right. A 12g bag of freshly ground Arabica brewed for four minutes gives you a filter-strength cup that sits comfortably alongside a cafetière. A 7.5g bag gives you brown water with good intentions.
We are all for spending thousands of pounds on laboratory-like equipment and getting a PhD in barista skills to produce the perfect cup. Genuinely. But sometimes that just is not practical on a campsite, in an office, or when you simply want a quick proper coffee at seven in the morning and the grinder is going to wake the whole house. Nobody is asking you to hand in your V60. Keep it. Use the bags for the other 40% of your week.
Coffee bags vs instant vs French press
|
Coffee bags |
Instant coffee |
French press |
| What is in your cup |
Ground coffee brewed in the mug |
Dried coffee extract, rehydrated |
Ground coffee brewed in the jug |
| Time to a cup |
3 to 4 minutes |
Under a minute |
About 4 minutes plus grinding |
| Kit needed |
Mug, spoon, hot water |
Mug, spoon, hot water |
Cafetière, grinder, kettle |
| Grind required |
None, pre-portioned |
None |
Coarse |
| Washing up |
None, bag goes in the food bin |
None |
Jug, plunger, wet grounds |
| Typical dose |
12g in ours, around 7.5g elsewhere |
1 to 2g of soluble powder |
About 30g per 500ml of water |
The interesting column is the middle one. A coffee bag brews for the first time in your mug. Instant coffee is a finished brew, made in a factory, dried out and posted to you. What you do in your kitchen is add water back to it. The extract is dried by being sprayed into hot air down a tower, or frozen to minus 40°C and dried under vacuum.
A cafetière and a coffee bag are doing the same job by the same method. Coarse grounds, hot water, full immersion, a mesh filter holding the solids back at the end. Even the timing lines up.
Which leaves one real difference between them, and it is the washing up. Clearing up after a French press exposes one of the great mysteries of life. Is it too wet for the food bin, or too grainy for the sink?
When a coffee bag beats instant
Any time you want brewed coffee and the kit is not there. That covers more of the week than most people expect.
You are in a rented cottage with a kettle, two mugs and a jar of something beige that has been in the cupboard since 2019. You are in a campervan at half six with the sun coming up and no intention of grinding anything. You are in an office where the machine is one floor down and permanently occupied. You have got a boat, a tent, a hotel room, a hospital waiting room, a shed. Or you are simply on the sofa at nine at night, and the mug is achievable but the plunger and its damp sludge are not.
The bags travel because there is nothing to pack. Our individually enveloped Definitely Decaf case of 50 was built for food service and then bought by everybody, because a foil envelope in a coat pocket is the whole system. Grinder, scales, filter papers, a kettle with a swan neck, all of it stays at home. Unless you are the sort who takes a burr grinder to a music festival, in which case we salute you, and your very heavy rucksack.
What are the best coffee bags to buy?
Judge them on four things, in this order.
- Dose. Look for the gram weight per bag on the box. 12g brews a proper mug. Anything near 7.5g is being economical with your morning.
- Contents. It should say 100% Arabica ground coffee and nothing else. Some coffee bags historically blended soluble powder in with the grounds.
- Shape. Pyramid over flat, so the grounds have room to expand.
- What the bag is made of. Corn-starch mesh composts in your food waste bin. Plastic mesh does not.
Our four caffeinated blends all run the same 12g fill: Breakfast Blend for caramel and hazelnut first thing, Deliciously Dark for an intense low-acid cup after dinner, plus Striking El Salvador and the enveloped Revive case. They all live on the coffee bags hub with the decaf.
Two people who do not work here have picked ours out. BBC Countryfile put our Definitely Decaf bags top of its decaf coffee bags category in July 2025. Olive Magazine ranked us first of ten coffee bags in 2024 and measured the dose while it was there. The full comparison, bags against beans, ground and pods, is in our best decaf coffee UK roundup.
Do supermarkets like Aldi sell coffee bags?
Yes. Aldi has sold coffee bags under its own Alcafé label, currently a Fiery Java 10-pack. Asda, Morrisons and Sainsbury's list them too, and Sainsbury's does an own-label version. Coffee bags are a normal supermarket line, not a specialist buy. Prices and line-ups move about, so the box in front of you is the one to read.
Where ours differ is the fill and the decaf. Every Raw Bean bag carries 12g of 100% Arabica against a category norm nearer 7.5g, and the decaf is done by Swiss Water rather than with a solvent. So turn over whatever box you pick up and find the grams per bag. That figure, not the brand on the front, decides the cup.
Why are coffee bags not more popular?
Because instant got there first and never left. Four UK households in five buy instant coffee to drink at home, and the British Coffee Association picks out the over-65s in particular. Against a jar in four kitchens out of five, and around 98 million cups drunk here every day, a newer format has a long climb.
The category also spent years undermining itself. Coffee bags were invented to give people instant's convenience while keeping the taste of brewed coffee. Half of them then arrived underfilled, so people tried one, shrugged, and went back to the jar. You do not get many second chances at somebody's breakfast.
Coffee bags in decaf, and why that matters at night
A decaf coffee bag lets you have a real brewed coffee after dinner. Ours use the Swiss Water Process, which removes 99.9% of the caffeine using water, temperature and time, with no chemical solvents. A cup carries roughly 2 to 7mg of caffeine, against 80 to 100mg in a regular coffee. On the European Food Safety Authority's working figures a 200ml cup of decaf holds about 4mg, and EFSA puts the single dose that may affect sleep in some adults at 100mg. The maths is on decaf's side.
That is a comparison rather than a promise, and it is the one worth having in front of you at nine at night. What 2 to 7mg actually does to sleep we go into properly, with the evidence, in can you drink decaf coffee at night, and the full milligram breakdown against espresso, black tea and green tea sits in how much caffeine is in a decaf coffee. If you want the process itself, we have written up how Swiss Water decaf is made. The late cup has a page of its own: Nightcap.
Our Definitely Decaffeinated bags are single origin Arabica from Quindío in Colombia, 12g a bag, smooth and creamy with dark cocoa and walnut. They sit with the enveloped case in decaf coffee bags. If you would rather grind your own decaf, start with the decaf coffee beans buying guide.
Boil a kettle, find a mug, take life one cup at a time.
