If your purchase order says “11 oz mug, 36 per carton” and nothing else, you have already handed control of the outcome to whoever packs it: usable capacity is not brim capacity, a carton cube quoted from memory is how containers get rolled, and a tolerance nobody wrote down cannot be enforced at inspection. This is the reference sheet we send buyers who want the numbers before they approve artwork.
Capacity: Brim, Usable and What You Actually Sell
This is the first place orders go wrong. A mug sold as 11 oz holds 325 ml to the brim, but only 280-290 ml of usable volume once you leave 1.5-2 cm of headspace, which is what a cafe actually pours. The same gap runs through the range: an 8 oz mug is 237 ml brim and about 205 ml usable, a 12 oz is 355 ml and about 305 ml, a 15 oz is 444 ml and about 385 ml, and a 20 oz is 591 ml and about 510 ml. Usable capacity lands at 85-88% of brim in almost every shape, and a thick-walled or heavily tapered body pushes it lower. Weight follows the same curve: an 11 oz mug runs 320-360 g unfilled and a 15 oz runs 420-470 g. Quote both figures on the artwork sheet, because a buyer who measures 280 ml will not accept “the box says 11 oz” as an answer.The Five Tolerances Worth Writing Into a PO
Five numbers do most of the work in a ceramic mug order. Fired rim diameter: plus or minus 2%, which is plus or minus 2.6 mm on an 80 mm rim, and the figure that decides whether a lid or a coaster still fits. Height: plus or minus 1.5 mm, because a 2 mm step is visible when six mugs sit in a row. Capacity: plus or minus 3%, which on an 11 oz mug is roughly 10 ml and is what keeps a printed capacity claim defensible. Wall thickness: 3.5-4.5 mm on the body and 8-12 mm on the handle, since a thinner wall chips at the rim while a thicker one adds freight for no benefit. Handle attachment: a 5 kg static pull test on the finished piece. Glaze safety belongs on the same page as a pass or fail rather than a tolerance: lead and cadmium limits tested on the finished glaze, not on the raw material.Cartons, CBM and the Container Sum
Carton maths decides whether a container closes. A master carton of 36 individually boxed 11 oz mugs measures about 520 x 380 x 400 mm, which is 0.079 CBM, and weighs roughly 14 kg. A 20GP carries about 28 CBM usable once dunnage and door clearance are allowed for, so it takes roughly 350 cartons, or 12,600 mugs. A 40HQ carries about 68 CBM usable and takes roughly 860 cartons, or 30,960 mugs; at 14 kg each that is about 12 tonnes, inside the payload. Bulk packing without inner boxes moves everything: 48 pieces in a carton of about 0.10 CBM gives roughly 280 cartons on a 20GP, or 13,400 mugs. Work the sum as usable CBM divided by carton cube, then round down 5% for pallets and gaps. Assuming 0.06 CBM instead of 0.079 is a 30% error, and that error arrives as a rolled booking.Lead Time by Stage
Lead time is four stages, and the total is the number that belongs in the contract. Sampling runs 7-12 days for a stock shape and 10-15 days when a new mould is involved, and the clock stops until artwork is approved in writing. Production runs 25-35 days for 10,000 to 30,000 pieces; the same order placed in the pre-holiday window from October can run 40 days. Cartoning and inspection adds 5-7 days before the vessel books, because inspection happens after packing rather than before it. Sea freight from China runs 30-38 days to the US East Coast and 28-35 days to Northern Europe, port to port. Add the four stages and a first order placed today is typically a 70-90 day exercise door to door. The stages that actually slip are artwork approval, a glaze batch that has to be re-run, and vessel space in peak season, not the firing.Where the Unit Cost Sits
On a plain-glazed 11 oz mug the factory cost splits in a fairly stable way. Clay and glaze account for 18-25%, forming 12-18%, firing 12-15%, decoration 10-20%, packaging 8-12%, and the remainder covers QC, overhead and margin at 20-25%. Two lines move the unit cost more than anything else, and both sit on the outside of the mug: decoration and packaging. A one-colour screen print sits at the bottom of the decoration band while multiple decals or hand-painting sit at the top, and a moulded pulp divider inside the carton can add more per piece than the print itself. That is a trade worth making deliberately. If the artwork is simple, spending the difference on packaging rather than on a heavier print lowers the breakage claim, and replacing a broken mug costs far more than the heavier carton does.Three Ways These Numbers Stop Adding Up
Three failures repeat across almost every first order. First, brim capacity quoted as usable capacity: the buyer measures 280 ml in a mug billed as 11 oz and the return rate follows, so write both figures on the spec sheet. Second, carton cube taken from a previous supplier: 0.06 CBM instead of 0.079 is a 30% shortfall and the load plan fails at the port, so ask for the measured carton rather than the nominal one. Third, glaze colour drifting between batches: a second shipment that reads slightly greener beside the first gets returned even though every piece passes inspection on its own, so hold Delta E under 1.5 and approve a retained sample, then test each new batch against that sample instead of against a photograph.Put the Numbers in the Purchase Order
A mug order is a set of numbers before it is a design. Brim and usable capacity, five tolerances, a measured carton cube, four lead-time stages and a cost split that names decoration and packaging are enough to make a first order predictable, and they give an inspection report something concrete to measure against. Découvrez notre gamme de mugs and ask for the specification sheet per SKU, because that sheet is the part of the order that survives the email thread.