What size mug to buy

Rev Mug — Coffee and tea mugs as a product category | revmug.com

What this page is

An independent, measurement-based reference on mug sizes and materials, built from published capacity, firing and safety figures with the arithmetic shown in place.

What it is not

Not a shop, not a paid product ranking, and not affiliated with any mug maker, retailer or previous holder of this domain.

325 mlStandard US coffee mug, 11 fl oz

60–500 mlCapacity range covered, demitasse to oversized

29.57 mlOne US fluid ounce — the conversion behind every label

Start from the serving you actually pour

A mug fits when your usual drink fills it to roughly 80 percent.

Take the most common case: a 12 fl oz serving poured into the large 15 fl oz (444 ml) diner mug. That fill level is exactly 80 percent, and it leaves 3 fl oz (89 ml) of headspace — room for milk, for foam, and for walking across the room without spilling. The same logic scales down: an 8 to 9 fl oz pour is at home in the standard 11 fl oz (325 ml) mug.

Beware the coffee maker's arithmetic. A '12-cup' drip machine counts a cup as 5 fl oz (150 ml), so a full reservoir is 60 fl oz (1.77 L) — only about five real mugs of 355 ml. If you brew for two people who each drink two mugs, the machine's label overstates your plan by more than half.

Brewing ratio ties size to taste. The golden-cup ratio calls for 55 g of coffee per litre of water, plus or minus 10 percent — about 16.5 g of grounds for a 300 ml mug. A mug far bigger than your serving tempts weak coffee; one too small concentrates it.

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The size ladder, from 60 to 500 ml

Six vessel classes cover nearly everything sold as a cup or mug.

At the bottom rung sits the espresso demitasse at 60 to 90 ml — two to three fluid ounces, sized for a single or double shot. Above it, the cappuccino cup holds 150 to 180 ml, and the latte mug spans 240 to 350 ml for milk-heavy drinks.

The middle of the ladder is where daily coffee lives: the standard US mug at 325 ml (11 fl oz) and the large diner mug at 444 ml (15 fl oz). Past them sits the oversized class around 500 ml, better suited to long tea sessions than to espresso-based drinks.

You can sanity-check any claimed capacity with a ruler. In a mug with an 85 mm inner diameter, 300 ml of liquid stands about 53 mm deep; a vessel that claims 300 ml but fills shallower is measuring to the rim, not to the drinking line. The full ladder with ounce conversions lives on the size chart page.

Espresso or ristretto: 60–90 ml demitasse
Cappuccino or small flat white: 150–180 ml cup
Latte or milky tea: 240–350 ml mug
Daily filter coffee, 8–9 oz pour: 325 ml standard mug
Daily filter coffee, 12 oz pour: 444 ml diner mug
Long tea sessions or soup: about 500 ml oversized mug

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Mug sizes at a glance

Six vessel classes and the servings each one suits
Vessel	Capacity (ml)	Capacity (fl oz)	Best suited to
Espresso demitasse	60–90 ml	2–3 fl oz	Single or double espresso
Cappuccino cup	150–180 ml	5–6 fl oz	Cappuccino, small flat white
Latte mug	240–350 ml	8–12 fl oz	Latte and milk-heavy drinks
Standard US mug	325 ml	11 fl oz	An 8–9 fl oz pour with headspace
Large diner mug	444 ml	15 fl oz	A 12 fl oz pour at 80% full
Oversized mug	about 500 ml	about 17 fl oz	Long tea sessions, soup

Six vessel classes and the servings each one suits

Terms worth knowing

Headspace: The intentional gap between the drinking line and the rim. A 12 fl oz serving in a 15 fl oz (444 ml) mug leaves 3 fl oz (89 ml) of it — room for milk, foam and safe carrying.
Demitasse: A small cup of 60 to 90 ml for espresso; the name is French for 'half-cup'. Anything larger lets a shot cool before it is finished.
Machine cup: The unit drip coffee makers count in: 5 fl oz (150 ml), not a kitchen cup. A 12-cup machine therefore holds 60 fl oz (1.77 L).
Golden-cup ratio: The brewing benchmark of 55 g of coffee per litre of water, plus or minus 10 percent. For a 300 ml mug that works out to about 16.5 g of grounds.
Drinking line: The fill level you actually use, below the rim. Capacity to the drinking line — not the advertised rim figure — is what a mug gives you in daily use.
Leach limit: The maximum migration of lead or cadmium from a glaze into food. Under FDA testing, food-contact ceramicware must stay under 0.5 ppm lead and 0.25 ppm cadmium.

Choose in five steps, ten minutes total

Work through the steps in order; each one names the classic mistake it prevents.

The sequence matters because each step narrows the next. Volume first, material second, verification last — reversing that order is how kitchens fill with mugs that look right and pour wrong.

None of the steps needs special equipment. A scale that reads grams and a jug you already own are enough, and the same scale reappears in the verification step described on the measuring page.

Step 1 — Weigh your usual serving (about 2 minutes). Pour your normal coffee into a jug on a kitchen scale: 1 g of a water-based drink is 1 ml. Prevents the overflow — buying a mug smaller than your actual pour.
Step 2 — Add headspace (under 1 minute). Divide the serving by 0.8 to get target capacity; a 300 ml serving wants about 375 ml. Prevents the slosh — a brim-full mug that spills between kettle and desk.
Step 3 — Check the machine math (about 1 minute). A 12-cup drip label means 60 fl oz (1.77 L) of 5 oz cups, roughly five 355 ml mugs. Prevents the five-ounce cup — planning around a label instead of a volume.
Step 4 — Pick the wall material (about 2 minutes). Match firing temperature and wall thickness to your microwave and dishwasher habits. Prevents the hairline crack — thermal stress in a mug never meant for rapid reheats.
Step 5 — Verify the candidate (about 3 minutes). Fill the mug with water on a scale to the level you would actually drink from, and read millilitres directly. Prevents the lying label — capacity quoted to the rim rather than to the drinking line.