One number does most of the work in coffee: the weight of water divided by the weight of dry coffee. Get it right and almost everything else becomes a small adjustment. Get it wrong and no amount of grinder tuning will save the cup.
Why weight and not scoops
A tablespoon of coffee varies between 4 and 7 grams depending on roast level, grind size and how the spoon is filled. That is a 75 percent swing — larger than the difference between a weak cup and a strong one. A 15 pound kitchen scale with gram resolution costs less than a bag of beans and removes the variable entirely.
Water is easier: 1 ml of water weighs 1 g at room temperature. So a 300 ml mug is 300 g of water, which means you can use a volume measure for water and a scale for coffee without introducing error.
The default: 1:16
Sixteen grams of water per gram of coffee. It produces a cup in the 1.3 to 1.45 percent TDS range, which is where most people land when they say a cup tastes normal. It works for pour over, drip, French press and AeroPress with only grind and time adjustments.
Start every new coffee at 1:16. Change one variable per cup. If it tastes weak, go to 1:15. If it tastes muddy or bitter, go to 1:17. Two steps is usually enough to land.
| Ratio | Strength | Best for |
|---|---|---|
| 1:12 | very strong | Cold brew ready-to-drink, iced coffee |
| 1:14 | strong | Small cups, dark roasts |
| 1:16 | standard | Pour over, drip, French press, AeroPress |
| 1:17 | light | Large batches, light roasts, subtle coffees |
| 1:18 | very light | Cupping, competition-style filter |
Ratios by method
These are starting points, not rules. The espresso ratio is expressed differently because the water is the beverage, not the solvent.
| Method | Ratio | Example dose |
|---|---|---|
| Espresso | 1:2 | 18 g in, 36 g out |
| Moka pot | 1:10 | 15 g in, 150 g out |
| AeroPress | 1:15 | 15 g in, 225 g water |
| V60 / pour over | 1:16 | 20 g in, 320 g water |
| Drip machine | 1:16 | 60 g per 1 L |
| French press | 1:15 | 30 g in, 450 g water |
| Cold brew concentrate | 1:8 | 110 g per 890 g water |
| Cold brew ready-to-drink | 1:14 | 70 g per 1 L |
Adjusting for taste
If the cup is weak and thin but not bitter, increase the dose. If it is weak and also bitter, the problem is extraction, not ratio — grind finer or brew longer, and leave the ratio alone.
Sour and sharp means under-extracted: grind finer, raise the temperature, or extend the brew time. Bitter and drying means over-extracted: the opposite. Changing the ratio moves strength; changing grind and time moves extraction. Confusing the two is the reason people spend months chasing a cup that never improves.
- Weak + not bitter -> more coffee
- Weak + bitter -> finer grind or longer brew
- Sour -> finer grind, hotter water, longer brew
- Bitter -> coarser grind, cooler water, shorter brew
Scaling a recipe
Water weight equals coffee weight times the ratio. For 6 cups of drip at 150 ml each, you need 900 g of water, which at 1:16 means 56 g of coffee.
Going the other way: if you have 22 g of beans left and want a standard cup, use 352 g of water. This is the calculation the ratio calculator exists to remove, and it is the one people get wrong most often when they are half awake at 6am.