Good filter coffee does not require expensive equipment. It requires four settings to be right and consistent. Once those benchmarks are in place, the same cup repeats itself every morning.
1. The ratio: 60 grams per litre
This is the starting point, and by far the most important. The international reference is roughly 60 g of coffee per litre of water, or 6% coffee in the cup.
In practice, for a 250 ml cup, count 15 g of coffee. For a 500 ml brewer, 30 g. For a litre, 60 g.
Use a scale, at least for the first few weeks. A tablespoon of coffee can weigh anywhere from 5 to 12 g depending on grind and packing: that is the main source of inconsistency for most people. A kitchen scale accurate to 1 g is enough.
This ratio is not a rule about strength but about concentration. If your coffee is too strong, do not coarsen the grind: reduce the dose or add water after brewing.
2. The grind: medium, like sand
For filter, aim for a medium grind, close to beach sand or caster sugar. Too fine and water passes too slowly and over-extracts: the cup turns bitter and drying. Too coarse and water runs straight through without taking anything: the cup is sour, hollow, watery.
The grind is your main correction tool. Remember these two reflexes:
- Bitter cup, dry on the finish: the grind is too fine. Coarsen it.
- Sour, flat cup lacking substance: the grind is too coarse. Make it finer.
If you can, grind just before brewing. Ground coffee loses most of its volatile aromatics within about fifteen minutes. It is the single habit that changes cup quality the most, ahead of the choice of coffee.
3. The water: between 92 and 96 °C
Boiling water scorches coffee and extracts bitter compounds. Lukewarm water under-extracts and gives a sour cup.
Without a thermometer, the method is simple: bring the water to a boil, take it off the heat, wait thirty to forty-five seconds. You will be in the right range.
Water quality matters as much as temperature. Very hard water flattens aromatics and scales up equipment; fully demineralised water gives a lifeless cup, because minerals take part in extraction. Lightly mineralised spring water is the best compromise. If your tap water is hard, a simple filter jug improves the result noticeably.
4. The time: two to four minutes
For a percolation method such as a V60 or Chemex, full extraction should take between two and a half and four minutes depending on volume.
Start by wetting the grounds with twice their weight in water, and let them swell for thirty seconds. This is the bloom: it releases the carbon dioxide trapped in freshly roasted coffee, which would otherwise repel water and make extraction uneven. Then pour the rest in a slow stream, in gentle circles, without digging into the coffee bed.
If the flow is much faster or slower than expected, leave everything else alone: adjust the grind only.
The correction table
One variable at a time, or you will not know what worked.
- Too bitter: coarser grind, or slightly cooler water, or shorter time.
- Too sour: finer grind, or hotter water, or longer time.
- Too strong: less coffee, or more water.
- Too weak: more coffee — never a finer grind.
Adapting to the coffee
The benchmarks above suit most coffees. Two adjustments are worth making.
On a high-altitude washed coffee, sharp and clean, you can go up towards 95-96 °C without risk: heat helps extract body. That is the case for most of our coffees of the Americas.
On a natural coffee, richer in sugars, drop towards 92 °C and shorten slightly: these coffees quickly turn heavy when pushed. To understand why, see our article on processing methods.
Finally, a freshly roasted coffee degasses heavily and extracts poorly in its first days. Wait three to five days after roasting, and store it properly: our storage guide covers the most common mistakes.
To put this into practice, browse the selection in the Coffees collection.