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Optima Cup Paper & PET drinkware from Türkiye

Cup volume calculator: oz to ml

Convert cup sizes between US fluid ounces and millilitres, work out the volume of a cup you are holding from its dimensions, and see which of our cups and lids it matches.

1 US fluid ounce = 29.5735 ml. Cup sizes are named in US fluid ounces, not imperial ounces.

Why the ounce and the millilitre never quite line up

One US fluid ounce is 29.5735 millilitres, so eight of them come to 236.6 ml. Yet almost every supplier in the world sells that cup as a 240 ml cup, and a 12 oz cup is offered as 350 ml rather than 354.9 ml. Neither figure is wrong. The ounce name is a trade size that has been rounded to a sensible serving, while the millilitre figure on a specification sheet is the volume the cup is intended to be filled to. The calculator above shows you both columns side by side so you can see exactly where the difference comes from instead of guessing.

Fill capacity is not the same as brim-full volume

Pour water into a cup until it reaches the rim and you will always get more than the number printed on the case. A cup has to leave room for a lid, for foam on a cappuccino and for a hand that is carrying it across a room. Manufacturers therefore quote the fill capacity, measured to a fill line a little below the rim. When you enter outside measurements into the second tab, the tool returns the geometric brim-full volume of a truncated cone — a clean upper bound. It is the honest number for what you measured, and it will sit above the trade size of the cup you are comparing it with. That gap is normal and it is the reason we match your measurements to our catalogue by dimension rather than by volume.

The rim diameter decides the lid, not the size name

Buyers lose more money on mismatched lids than on almost any other detail. What matters is the diameter across the rim. On our paper lids, the 12 oz size sits on an 80 mm rim while the 14 oz and 16 oz cups share a 90 mm rim and therefore share a lid. On the clear PET side the picture is even simpler: every one of our PET lids is 95 mm, so a single lid covers the whole cold-drink range from 8 oz to 22 oz. If you are consolidating an order, that one fact usually removes a line item or two from your purchase list. Measure the rim, read the result above, and you will know what fits before you ask us anything.

Choosing a size for the drink you actually serve

Espresso and Turkish-style servings sit at the small end, around 4 oz. A flat white or a filter coffee to go is comfortable at 8 oz, which is why that size dominates café orders. Twelve and fourteen ounces cover the large hot drinks and the iced-coffee range, and sixteen ounces is where milkshakes, smoothies and long cold drinks live. Vending machines are their own case: those cups are dimensioned for the machine's dispenser column rather than for a hand, so if you are buying for vending, tell us the machine and we will confirm the fit.

Ordering the size you settled on, with your own brand on it

Once you know the size, the rest is straightforward. We print in six flexo colours as standard, and on double-wall cups we can also run CMYK offset, which lifts the colour limit entirely for photographic artwork. Production, quality control, packing and shipping all happen inside the same company in Türkiye, so you are dealing with the people who actually run the line rather than an agent in between. Send us the size, the quantity and your artwork and we will reply with a proforma; freight terms are set by the incoterm you prefer.

Cup size chart: oz to ml

Every figure below is the real specification of a cup we run — not a generic table copied from elsewhere.

Size Fill capacity Arithmetic conversion Rim Ø Height Product
4 oz 100 ml 118.3 ml 62 mm 62 mm Single-wall paper cup 100 ml (4 oz)
6 oz 150 ml 177.4 ml 70 mm 79 mm Single-wall paper cup 150 ml (6 oz)
7 oz 180 ml 207 ml 70 mm 81 mm Single-wall paper cup 180 ml (7 oz)
7.5 oz 190 ml 221.8 ml 70 mm 92 mm Single-wall paper cup 190 ml (7.5 oz)
8 oz 240 ml 236.6 ml 80 mm 87.5 mm Single-wall paper cup 240 ml (8 oz)
9 oz 250 ml 266.2 ml 76 mm 97 mm Single-wall paper cup 250 ml (9 oz)
12 oz 350 ml 354.9 ml 80 mm 118 mm Single-wall paper cup 350 ml (12 oz)
14 oz 400 ml 414 ml 90 mm 106 mm Single-wall paper cup 400 ml (14 oz)
16 oz 480 ml 473.2 ml 90 mm 136 mm Single-wall paper cup 480 ml (16 oz)

The two millilitre columns differ on purpose: the trade name rounds to a practical serving size, while the arithmetic column is the exact ounce conversion.

Frequently asked questions

How many ml is an 8 oz cup?

An 8 oz cup holds 240 ml as a fill capacity, which is the figure the trade uses. The strict arithmetic conversion is 236.6 ml, because one US fluid ounce is 29.5735 ml; suppliers round to 240 ml because that is the volume the cup is designed to be filled to.

How many ml is a 12 oz cup and a 16 oz cup?

A 12 oz cup is 350 ml and a 16 oz paper cup is 480 ml in our range. The arithmetic conversions are 354.9 ml and 473.2 ml, so the trade figures round in different directions depending on the cup geometry — always work from the specification sheet rather than from the ounce name.

How do I measure a cup correctly?

Measure the outside of the cup at three points: straight across the rim, straight across the base, and from the base to the top edge. Rim diameter and height are the two that matter for identifying a cup, because they determine both the shape and the lid.

Which lid fits which cup?

The rim diameter decides the lid, not the size name. Our paper lid for 12 oz is 80 mm, while 14 oz and 16 oz share a 90 mm rim and take the same lid; every PET lid we make is 95 mm, so one lid covers the whole cold range from 8 oz to 22 oz.

Why is the calculated volume higher than the cup size?

Because the calculator gives the brim-full volume of the outside dimensions, while the name of a cup refers to its fill capacity. A cup must leave headroom for a lid and for carrying, so the fill line sits below the rim and the printed capacity is always the smaller number.

Know your size? Get a quote

Tell us the size, the quantity and your artwork; we produce on our own line and reply with a proforma.

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