Phin Coffee Ratio: Why 1:5, and When to Break It

Where 1:5 comes from

A standard 120 ml phin, filled to a sensible level, takes about 20 g of coffee and about 100 ml of water. That is not a recipe someone designed — it is what the device holds.

The chamber has to be at least a third full for the bed to seal properly against the press plate. Below that, water runs round the edges and through in ninety seconds. Above about half full, there is not enough headroom left for the water. Those two constraints put you at roughly 20 g in a 120 ml phin, and the water volume follows.

So the ratio is a consequence of the hardware, and the drinks were built around it afterwards.

How much coffee goes in a phin

Twenty grams in the standard 120 ml phin. Larger phins take proportionally more, and the coffee-to-water ratio stays close to 1:5 across all three common sizes.

Phin	Coffee	Water	Ratio
120 ml — the café standard	20 g	100 ml	1:5
200 ml	30 g	160 ml	1:5.3
350 ml	50 g	280 ml	1:5.6

Every recipe on this site assumes the 120 ml phin.

What actually matters is not the dose but the depth: the chamber wants to end up between a third and a half full. That is what lets the bed swell against the press plate and seal. Under a third, water runs round the edge of the bed instead of through it; over a half, there is no headroom left for the water. If your phin is an odd size, fill it to a third and work back from there rather than trusting a number off a page like this one.

Measuring without a scale

Roasted ground coffee has a bulk density of roughly 0.30–0.41 g per millilitre, measured across roast levels and grind sizes. That puts a level tablespoon somewhere between 4.4 and 6.1 g:

Dose	Level tablespoons
20 g	about 4
30 g	about 6
50 g	about 10

Three tablespoons is the figure repeated most often for a 20 g dose, and at these densities three level tablespoons is closer to 15 g. The spread comes from both roast level and grind size — the measurements found finer grinds and lighter roasts packing denser — so a spoon can put you a few grams either side of 20 g, which is the difference between 1:5 and 1:6.

None of which is a reason to buy a scale if you do not want one. Weigh the dose once, note where it comes to in the chamber, and use the chamber from then on. The phin calculator does the arithmetic for a phin of any size.

What a 1:5 ratio actually does

Method	Typical ratio
Espresso	1:2
Phin	1:5
Moka pot	1:7
Pour-over / drip	1:16
French press	1:15

Those are brewing conventions rather than measurements, and the two are worth separating. For drip coffee there is a published target: 1.15–1.35% dissolved solids at 18–22% extraction, the band the Specialty Coffee Association’s brewing control chart marks as ideal. For a phin there is no equivalent figure. We found no published measurement of the strength of a phin brew, so anyone quoting one to three significant figures is estimating.

What the ratio and the four-to-six-minute contact time imply together is a cup several times more concentrated than filter coffee and well short of espresso. The result is thick and genuinely bitter, and it is not meant to be drunk neat by most people.

That is the design. Two things happen to it afterwards:

1. Condensed milk — about 30 ml of it, about 54% sugar by weight, which coats the palate and needs something strong to cut through.
2. Ice — a full glass, which adds water as it melts. Probably 60–100 ml, though that depends on the glass and how fast you drink it, and we have not measured it.

Brew at 1:16 and after both of those you are drinking sweet, faintly coffee-flavoured milk. Brew at 1:5 and the coffee is still the loudest thing in the glass at the bottom of it.

The ratios to actually use

Drink	Ratio	Dose (120 ml phin)
Cà phê sữa đá	1:5	20 g / 100 ml
Cà phê đen đá	1:5.5	22 g / 120 ml
Cà phê sữa nóng	1:4	20 g / 80 ml
Bạc xỉu	1:5	12 g / 60 ml
Everyday black, no ice	1:7	18 g / 130 ml
Vietnamese arabica	1:8 to 1:10	16 g / 130–160 ml

Two of those deserve a word.

Cà phê sữa nóng is tighter, not looser. No ice means no dilution, so the brew is pulled shorter to compensate.

Bạc xỉu keeps the ratio and drops the dose. The coffee itself is brewed at normal strength — there is just less of it, because the drink is mostly milk. This is why bạc xỉu tastes like a proper coffee drink rather than a weak one.

When to break it

Going wider than 1:6 is the right move whenever milk is not doing the balancing. Black coffee, no ice, or a lighter roast all want more water per gram.

Arabica needs at least 1:8. Vietnamese arabica from Đà Lạt or Sơn La is a different coffee with a different job. Brewed at 1:5 it turns astringent and you lose every delicate thing you paid for. It is also worth asking whether a phin is the right brewer for it at all.

Going tighter than 1:4 produces something closer to a concentrate. Occasionally useful if you are making a large iced drink where a lot of dilution is coming, but at that point a Moka pot does the job more reliably.

The lever people forget

Ratio is not the only thing controlling strength. A 1:5 brew that runs through in ninety seconds is weaker than a 1:7 brew that takes five minutes, because the ratio only tells you how much water passed through the coffee — not how much it took with it.

If your coffee tastes thin at 1:5, the answer is usually not more coffee. It is a slower drip. See how to use a phin for the three levers that control it, and phin brew time for what to change when the drip is running away from you.

The rest of the method is collected under brewing.