Formula
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Immersion ratio
French press ratio
For a French press, start at 1:16.7: 30 g of coffee to 500 g of water, steeped 5 minutes. Every ratio in this page is grams of water per gram of coffee, so 1:16 means 16 g of water for each 1 g of ground coffee. Below are a table for four batch sizes, the reasons ratio works differently in immersion, and what to change when the cup is off. The calculator has a French press preset that does this arithmetic for any dose.
Measured result
Recipe calculation
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Calculated from the values above
Submit valid measurements to see the formula and assumptions.
Yield
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Extraction
Measured TDS is optional.
Dilution
Add current and target TDS to calculate.
Assumption
Mass is metric internally; rounding is display-only.
Why ratio is the strength lever here
In a French press every gram of water touches every gram of coffee for the whole steep. Nothing drains away mid-brew and fresh water never arrives. So the water you add decides the concentration, and the ratio is the most direct way to set strength. A shorter ratio such as 1:15 gives a stronger cup. A longer one such as 1:17 gives a lighter cup.
Ratio does not set extraction by itself. How much dissolves also depends on grind, steep time and water temperature. Hold those still and change only the ratio, and you move strength with little change to what the coffee tastes of. The extraction guide explains why those two measurements are different.
Ratio table by batch size
Water is the number you pour. Coffee is water divided by the ratio. Tablespoons are approximate: they assume about 5 g of coarsely ground coffee per level tablespoon, and real spoons and grinds vary a lot. Weigh when you can.
| Water | Batch | 1:15 coffee | 1:16 coffee | 1:17 coffee |
|---|---|---|---|---|
| 250 g | 1 cup | 16.7 g (about 3 tbsp) | 15.6 g (about 3 tbsp) | 14.7 g (about 3 tbsp) |
| 500 g | 2 cups | 33.3 g (about 6.5 tbsp) | 31.3 g (about 6 tbsp) | 29.4 g (about 6 tbsp) |
| 750 g | 3 cups | 50.0 g (about 10 tbsp) | 46.9 g (about 9.5 tbsp) | 44.1 g (about 9 tbsp) |
| 1000 g | 1 litre | 66.7 g (about 13 tbsp) | 62.5 g (about 12.5 tbsp) | 58.8 g (about 12 tbsp) |
"Cup" here means 250 g of water, the size CupTune uses for planning. It is not the 150 ml marking on many coffee machines. One millilitre of water is close enough to one gram for brewing.
CupTune's French press preset sits between the 1:16 and 1:17 columns, at 1:16.7. For 500 g of water that is 30 g of coffee.
Retained water: less in the cup than in the kettle
Wet grounds hold water. CupTune uses an editable planning assumption of 2 g of water retained per 1 g of dry coffee, the same one the calculator uses. The true figure depends on the coffee, the grind and how hard you press, so treat it as approximate.
The arithmetic is short. Beverage = water − 2 × dose.
- 30 g in, 500 g water: 500 − 60 = about 440 g in the cup.
- 62.5 g in, 1000 g water: 1000 − 125 = about 875 g in the cup.
If you want a full 500 g cup, add the retained water on top: 500 + 60 = 560 g of water for a 30 g dose. Note this shifts the ratio to about 1:18.7 on brew water, so choose the dose first, then work out the water.
How ratio interacts with steep time and grind
CupTune's French press grind range is 900 to 1300 microns. That range is authored from CupTune's grind chart, and it is wider than any single grinder will hit. Treat it as a start.
- Longer steep or finer grind extracts more. Both raise strength a little and can add bitterness and sediment.
- Shorter steep or coarser grind extracts less and can taste thin or sour.
- Mesh filters pass fine particles into the cup. Grind sets how much sediment you get, not only how strong it is.
The practical rule is to change one thing at a time. If a cup is too strong but tastes clean, lengthen the ratio and leave time and grind alone. If it is too strong and harsh, change the grind or time instead, because a longer ratio only dilutes the harshness.
Fixes when the cup is off
- Weak and watery. Go one step shorter, for example from 1:17 to 1:16. Check you weighed the coffee, not scooped it.
- Too strong or heavy. Go one step longer. Do not change the grind in the same brew.
- Bitter and dry, even after a longer ratio. Coarsen the grind one notch, or shorten the steep by 30 seconds.
- Sour or flat. Grind a little finer or steep 30 seconds longer, and check water was near 94 °C.
- Muddy with silt at the bottom. Coarsen the grind, pour gently when you decant, and leave the last sip in the press.
- Less coffee than expected. That is retained water, not a leak. Use the arithmetic above.
These fixes are CupTune's rules of thumb for immersion, not measured results.
The recipe
This page's recipe is CupTune's Classic French press: 30 g of coffee, 500 g of water at 94 °C, a 20-second pour, a 220-second steep, a crust break and a slow plunge to 300 seconds. The step-by-step version is on the French press recipe page.
Evidence and limits
No standards body fixes a French press ratio. The 1:15 to 1:17 span, the 1:16.7 preset, the spoon conversion and the 2 g/g retention figure are CupTune's authored planning values. The table is plain division. The preset ratio and retention come straight from the calculator code. None of it was measured on your coffee.
Questions
What is the ratio for a 34 oz press?
A 34 oz (1 litre) press at 1:16 takes 62.5 g of coffee and 1000 g of water, which gives about 875 g in the cup. Leave a little headspace so the plunger clears the water.
Is 1:12 too strong for a French press?
It is stronger than anything here, around 83 g per litre. It is a taste choice, not an error, but expect more bitterness unless you coarsen the grind.
Does a bigger batch need more time?
Not by default. Keep the steep the same and watch the cup. A large press holds heat longer, so it may extract slightly more.