Moka Pot Ratio Calculator

How to use this moka pot ratio calculator

1. Pick your pot size. Moka pots are sold in "cups" that mean espresso-size servings of about 2 oz, not mugs. A 6-cup is a two-person pot, not a six-person one. If you're not sure which you own, fill the bottom chamber to the valve, tip it into a measuring jug, and match the millilitres against the size chart below.
2. Pick your roast. This is the control that actually moves the dose, and it's the one every other page leaves out. A level basket of dark roast weighs roughly a third less than the same basket of light roast, because dark beans are puffed up and brittle.
3. Set the grind. Medium-fine is the answer almost always. The other two options are there so you can see what they cost you.
4. Set the strength. The dose can't change — the basket holds what it holds — so strength moves the water instead. Stronger fills a little below the valve. Milder never adds water to the boiler; it tells you how much hot water to add to the finished coffee instead.
5. Brew off the steps. Everything recomputes as you change an input, there's no Calculate button, and you can copy the recipe, share a link that reopens it, or take the PDF brew card to the stove.

Why this moka pot calculator is different

Search moka pot ratio and you'll be told 1:10. Search a little harder and you'll be told 1:7, and 1:12, and 1:16, and 1:20 — sometimes by the same brand on the same page. Here is what the top of that search result actually claims:

That's a spread of 1:7 to 1:20 on one brewer. It is not that six of those seven sources are wrong. It's that the question is malformed.

• On a moka pot, you do not choose the ratio. The filter basket holds a fixed volume and the boiler fills to a fixed line. Both sides of the ratio are set by the hardware before you touch anything, so the ratio is an output. This calculator prints it as one.
• Roast level is a real variable, and it's missing everywhere else. Ground coffee runs about 0.30 g per cc when dark and 0.50 g when light. That is a 66 percent swing in what the same level basket weighs, and it is most of the reason the published doses disagree.
• It knows what your pot actually holds. Nine sizes, with the boiler volume to the safety valve and the basket capacity for each, plus a measure-your-own mode for the pots that aren't Bialettis.
• It tells you what lands in the cup, not what's on the box. About a third of the water stays in the grounds and the boiler. A 6-cup rated at 270 ml delivers closer to 204 ml.
• The math is tested on every build. A fixture suite reproduces the published per-size doses from Steampunk Coffee and the basket measurement from Home-Barista, checks that the printed dose, water and ratio can never contradict each other, and asserts that no setting can ever advise filling above the safety valve. If a change broke any of that, the build fails before it ships.

How it works (the math)

Three lines, and none of them start from a ratio:

water = boiler volume to the safety valve
dose  = basket volume x bulk density (roast, grind)
ratio = water / dose            <- an output, not an input

Bulk density is the part that does the work. Untamped ground coffee sits between about 0.30 g per cc for a dark roast and 0.50 g per cc for a light one. A 3-cup Bialetti has a basket of roughly 50 cc, so the same level basket holds 15 g of dark roast or 25 g of light — and a typical medium lands at 18 to 20 g, which is the figure most brew guides quote without ever saying which roast they weighed.

The yield is not the water you put in. Spent grounds hold on to a good deal of it, and the boiler never runs completely dry, so between 65 and 70 percent of the water reaches the top chamber. This calculator uses 68 percent.

Strength moves the water, never the dose. A moka pot needs a full basket to build pressure properly — an under-filled basket doesn't restrict the flow enough and you get weak, percolator-ish coffee rather than a stronger cup. So a stronger brew means slightly less water against the same dose, and a milder one means brewing normally and lengthening the cup afterwards. There is no setting here that fills the boiler above the safety valve, because that valve is a pressure release and covering it is a genuine burn risk.

A limitation worth stating plainly. Moka pots are not a standardised product. The figures here are modelled on the Bialetti Moka Express in aluminium, cross-checked against Bialetti's own published capacities. The 1 through 6-cup basket volumes are anchored on measured doses; the 9, 12 and 18-cup are extrapolated from that series. Measure your own pot once and the calculator stops modelling and starts reporting.

Moka pot size chart: water and coffee by pot

Moka pot "cups" are Italian espresso servings of about 2 oz, which is why a 6-cup pot fills two mugs rather than six. These are the figures the calculator uses, at a medium roast and a medium-fine grind.

Two things in that table are worth pausing on. Small pots brew stronger — a 3-cup runs near 1:8 while a 6-cup runs near 1:10.5, because the basket doesn't shrink in proportion to the boiler. And every pot delivers about a third less than its rating, which is why a 6-cup marketed at 270 ml gives you roughly 204 ml of coffee. The 9, 12 and 18-cup rows are extrapolated rather than measured; if you own one, use the measure-your-own mode above.

If you're choosing a size rather than checking one you own, our best moka pots guide covers which builds hold up and which gaskets you'll actually be able to replace in five years. For the technique itself, step by step, see how to use a moka pot.

Moka pot grind size

Medium-fine — finer than pour over, coarser than espresso, about the texture of granulated sugar or table salt. Blue Bottle, Stumptown, Steampunk and Starbucks all land in the same place on this, which is more agreement than they manage on anything else about moka pots.

The reason the window is narrow is pressure. A moka pot builds only about 1 to 1.5 bar, a fraction of an espresso machine's nine. Grind at espresso fineness and that modest pressure can't push through the puck: the brew stalls, the boiler keeps heating, and eventually the safety valve does its job in a way you will remember. Grind too coarse and water races through without extracting, giving a sour, thin cup that tastes under-baked no matter how long you leave it on the heat.

Grind also changes the dose, which is why it's an input above. Finer grounds pack a little more densely, so the same level basket holds slightly more coffee by weight. Our coffee grind size chart puts moka pot on the same micron scale as every other method, and if your grinder can't hold a setting between drip and espresso, the best burr grinders guide is the honest fix — a blade grinder produces dust and boulders simultaneously, and the dust is what clogs the filter plate.

Three worked examples

A 3-cup Bialetti, medium roast — the everyday case

Fill the boiler to the valve and you're putting in 150 ml. The basket takes about 18.5 g of medium roast. That's a ratio of 1:8, noticeably stronger than the 1:10 the internet quotes, and it yields about 102 ml — one proper mug, or two small Italian cups. If that reads strong to you, it is: the 3-cup is the size that most rewards a dark roast and a splash of hot water afterwards.

A 6-cup with a dark roast, for two

Same pot everyone owns, 300 ml of water. Switch the roast to dark and watch the dose fall from 28.5 g to 22.5 g — the basket hasn't changed, the coffee has. The ratio moves from 1:10.5 to 1:13.3, which is why a dark roast in a moka pot tastes smoother and less punchy than the same pot with a medium. Nothing is wrong; you've just brewed a different drink. If you want the intensity back, either grind a touch finer or use the Stronger fill.

A pot that isn't a Bialetti

Every other brand sizes its "cups" differently — a Bialetti Venus 4-cup holds 170 ml where a Musa 4-cup holds 150, and both are sold as four cups. Fill yours to the valve once, pour it into a measuring jug, and enter the number. Do the same with the basket if you want the dose exact rather than estimated. It takes a minute and it's the difference between a model of a moka pot and a measurement of yours.

Frequently asked questions

What is the coffee to water ratio for a moka pot?

Between about 1:8 and 1:11 on a medium roast, and your pot decides which. Fill the basket level and the boiler to the valve, and a 3-cup Bialetti lands near 1:8 while a 6-cup lands near 1:10.5 — small pots have proportionally larger baskets. Roast moves it again: the same 6-cup filled with a dark roast lands nearer 1:13, because a level basket holds less of a dark roast by weight. The widely quoted 1:10 is a fair average and a poor instruction, because you cannot act on it: the only way to hit a chosen ratio on a moka pot is to under-fill the basket, and an under-filled basket doesn't build enough pressure to brew properly.

How much coffee do I need for a 6-cup moka pot?

About 28 to 30 g of a medium roast, or 23 g of a dark roast, with 300 ml of water to the safety valve. The spread is the roast, not the recipe. In practice you don't need to weigh it at all: fill the basket to the brim, tap it to settle, sweep it level with a finger, and don't tamp. The basket is the measuring cup. Weighing is worth doing once so you know what your basket holds, and after that it's a check rather than a step.

How much coffee for a 3-cup or 4-cup moka pot?

Roughly 18.5 g for a 3-cup and 20 g for a 4-cup at a medium roast, against 150 ml and 200 ml of water respectively. Stumptown publishes 15 to 17 g for a 4-cup and Steampunk publishes 18 to 20 g for the same pot, and both are right — they weighed different roasts. Use the calculator above with your actual roast rather than picking one of the two.

Do you fill a moka pot with hot or cold water?

Hot, just off the boil. Starting cold means the base sits over the burner for several minutes while the coffee in the basket slowly bakes, and that is where the scorched, metallic edge in bad moka coffee comes from. Stumptown, Blue Bottle and Steampunk all preheat. Illy's own guide says cold, which works if your heat is low and your patience is good, but hot water is the more forgiving method and it cuts the time on the stove roughly in half. Use a towel — the base will be hot to assemble.

Should you tamp the coffee in a moka pot?

No. Level it, never compress it. A moka pot generates 1 to 1.5 bar against an espresso machine's nine, and a tamped puck simply will not let that pressure through. What you get is a stalled brew, a boiler that keeps building pressure with nowhere to send it, and eventually the safety valve venting. Fill the basket slightly mounded, tap it on the counter to settle the grounds, sweep the top flat with a finger, and wipe the rim clean so the gasket seals.

Why does the number on the box say 6 cups when I only get two mugs?

Because a moka "cup" is an Italian espresso serving of about 2 oz, and because the rating describes the pot's nominal capacity rather than what reaches the top chamber. Around a third of the water stays behind in the spent grounds and the boiler. A 6-cup Bialetti is rated at 270 ml and delivers closer to 204 ml, which is two mugs with a little left over, or two long blacks. It isn't a defect and it isn't false advertising, but nobody tells you before you buy.

Related tools

• Coffee to Water Ratio Calculator — the all-method hub, for drip, pour over, French press, AeroPress, cold brew and espresso.
• Coffee Grind Size Chart — where moka pot sits on the micron scale, next to every other method.
• Pour Over Coffee Calculator — dose, water, and a pour-by-pour schedule with the clock time for every pour.
• How Many Tablespoons of Coffee Per Cup? — when there's no scale in the kitchen, adjusted for what your grind and roast actually weigh.
• Coffee Water Temperature Calculator — your target brew temp, and the boiling point where you actually live.
• Browse all free coffee tools by Clara →

Gear worth having for a moka pot

A moka pot is a cheap brewer with two expensive failure points: the grind, and the pot itself.

• A pot whose parts you can replace. Gaskets perish, filter plates warp, and a moka pot is meant to last decades. That is most of the argument for a Bialetti over a lookalike — see best moka pots for which ones survive and which ones you'll be hunting parts for.
• A burr grinder. The grind window here is narrow and a blade grinder cannot hit it: it makes dust and boulders at once, the dust clogs the filter plate, and the pot chokes. Our best coffee grinders picks start at the cheapest burr worth owning.
• A roast that suits the pot. Moka pots brew hot and extract hard, which flatters a medium to dark Italian-style roast and can punish a delicate light one. Our bean picks mark which is which.
• A scale, once. You don't need one every morning — the basket is the measure. You need it once, to find out what your basket actually holds, so the number above becomes yours rather than a model's.

Sources & methodology

• Bialetti — Moka Finder — that a moka "cup" is an espresso serving of about 2 oz, and the rated capacity of each Moka Express size.
• Home-Barista — moka pot size and material — the 3-cup basket at about 50 cc, the 0.30 to 0.50 g/cc bulk density range for untamped grounds, and the compiled Bialetti capacity table.
• Steampunk Coffee — perfect moka pot brewing — per-size doses and water volumes (4-cup 18–20 g / 200 g, 6-cup 27–30 g / 300 g), and the 65–70% yield figure.
• Blue Bottle — moka pot brew guide — grind target, the no-tamp rule, and 3–6 minute brew time.
• Stumptown — how to brew in a moka pot — preheating the water, and the 4-cup dose.
• Honest Coffee Guide — moka pot size guide — the tazza definition and how to identify an unmarked pot.

Rated capacities come from Bialetti's own product listings, corroborated against the Home-Barista compiled dimension table. Boiler volume to the safety valve is 50 ml per rated cup, a figure three independent sources agree on. Basket volumes for the 1 to 6-cup sizes are set so the dose at a medium roast reproduces the published per-size doses; the 9, 12 and 18-cup basket volumes are extrapolated from that series rather than measured, and are flagged as such in the tool. Bulk density runs 0.30 to 0.50 g/cc by roast, with a modelled grind adjustment of ±0.02. Every figure is rounded once, at the display boundary, and the ratio is derived from the rounded dose and water so the card cannot contradict itself. A fixture test asserts the published doses and yields, sweeps all 675 combinations of pot, roast, grind, strength and cup for finite output, and fails the build if any setting could advise filling above the safety valve. Reviewed by Clara Bennett, CQI Q Grader. About Clara · Last reviewed September 13, 2026.

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