Why capacity causes disputes
A buyer orders 32 oz soup cups, receives cups marked 950 ml, fills them with soup to a sensible level and finds they hold noticeably less than the menu promised. Nobody lied: the plant quoted brim-full volume, the buyer assumed working volume, and the unit conversion added its own rounding. Most capacity disputes come from three sources: the unit, the measuring method and the model name. Each can be fixed on paper before an order is placed.
Units: ml, US fl oz, UK fl oz and liters
Partner plants in China specify capacity in millilitres. Buyers in the United States usually think in US fluid ounces, and storage products are often sold in liters or quarts. One US fluid ounce is about 29.57 ml; one UK fluid ounce is about 28.41 ml, so the same container converts to slightly different ounce figures depending on the market. Retail listings also round freely, which is why a 950 ml cup may be sold as 32 oz and a 1,000 ml box as 34 oz.
| Capacity | US fl oz (approx.) | Reference model |
|---|---|---|
| 350 ml | 11.8 | Export soup cup, 116x99x45 mm |
| 500 ml | 16.9 | Rectangular PP box, 170x115x34 mm |
| 750 ml | 25.4 | Rectangular PP box, 170x115x51 mm |
| 950 ml | 32.1 | Export soup cup, 117x82x141 mm |
| 1,000 ml | 33.8 | Rectangular PP box, 170x115x64 mm; three-compartment tray |
| 1,500 ml | 50.7 | Roast-meat box, 217x149x71 mm |
The conversions are arithmetic; the capacities are the plants' stated values. When you sell in ounces, decide whether you round down, to the nearest whole ounce or to a marketing size, and write that choice into your listing rules. Under-promising by rounding down is the safer habit.
Brim-full versus fill line
Brim-full capacity is the volume of liquid the base holds when filled exactly to the rim, without the lid. It is easy to measure, repeatable and what most plant cut sheets quote. Fill-line or working capacity is the volume you can actually put in and still close the lid, carry the box and avoid spills, usually some way below the rim. For soups and sauces the gap matters a great deal; for dry foods or salads it matters less, because a domed lid adds headroom.
A practical approach is to keep both numbers. The cut sheet states brim-full capacity, measured with water on the sample. The menu or listing states a working capacity agreed with the kitchen or brand, set by filling the sample with the real food to the level that closes cleanly. The desk records which figure is which in the specification so the plant, the inspector and the sales copy all use the same basis.
When the model number is not the capacity
Many series are named by capacity, but not all. One partner range of starch-based bowls shows the gap clearly: a bowl sold as model 380 measures 136x83x51 mm and is listed at 450 ml, model 500 at 136x82x62 mm is listed at 650 ml, and model 1000 at 175x125x67 mm is listed at 900 ml. The model number is a catalog name, not a measurement. Before a listing goes live, read the capacity column and confirm it on the sample. The starch-based containers page lists that range in full.
Compartments and divided trays
For divided trays, capacity is usually stated as a total. A clear PP three-compartment tray from a partner plant measures 218x188x42 mm with a stated 1,000 ml total; a large five-compartment tray at 232x232x47 mm is stated at 1,500 ml. Kitchens portioning rice, protein and vegetables need the volume of each compartment, not the total, so ask the plant for per-compartment figures or measure them on the sample. See divided fruit containers.
Storage containers and dry goods
For home storage, capacity is usually given in liters per piece, for example vacuum containers in sets of 0.5-2.0 L. Pet food bins are often sold by the weight of food they hold, such as a 20 lb bin, with a quart figure alongside. The weight a bin holds depends on the shape and density of the kibble, so public listings describe it as approximate. If you sell by food weight, test with the product your customers use and phrase the claim accordingly.
Capacity across a range, not one box at a time
Capacity decisions work best as a series. A takeout range built on one footprint, such as the partner series at 170x115 mm in 500, 650, 750 and 1,000 ml, gives a kitchen four portion sizes that share one lid and stack together in a delivery bag. The steps between capacities should match real portions on the menu, not round numbers in a catalog. If the most common dish fills a 650 ml box to the working line and spills over in the next size down, the gap between 500 and 650 ml is the one that matters, and it is worth checking with the real food before ordering.
Common capacity mistakes
- Comparing quotes on different bases. One plant quotes brim-full, another working volume; the cheaper box may simply be smaller.
- Converting once and rounding up. A 950 ml cup sold as 34 oz invites complaints; 32 oz is the honest figure.
- Ignoring the lid. A domed lid adds headroom for salads; a flat lid on a full soup cup leaves none.
- Trusting the model name. Read the capacity column and check it on the sample.
Writing capacity into the specification
- State the unit and the method: brim-full, without lid, water at room temperature.
- Record the measured value on the approved sample and a tolerance agreed with the plant.
- Add a working capacity if the product is sold by it, and how it was set.
- Fix the rounding rule for ounces or other units used in listings.
- Include a capacity check in the pre-shipment inspection.
Capacity, size and gram weight together define the model; the food container sizing guide explains how to choose capacities for a menu or range. Typical starting quantities run from a few mixed cartons from stock molds to 10,000-50,000 pieces per item for printed lids, confirmed in writing per program; see MOQ and lead time. Send the capacities you sell through the quote form and the desk will match them to measured reference models.