Container Load Calculator

Worked example

Four hundred and fifty cartons measuring 60 × 40 × 50 centimeters.

1. A 20 ft container takes 180 of these, and a 40 ft standard takes 400. Neither holds the whole order.
2. A 40 ft high cube takes 500, because the extra 30 cm of interior height allows a fifth layer of 50 cm cartons.
3. So this ships as one 40 ft high cube, arriving 90% full.

That high cube is the whole story here. The 40 ft standard and the high cube have identical floor space; the only difference is height, and it is worth 100 extra cartons on this particular box size.

The formula

For each of the 6 ways the carton can sit:
  per length = ⌊container length ÷ carton dimension A⌋
  per width  = ⌊container width  ÷ carton dimension B⌋
  per height = ⌊container height ÷ carton dimension C⌋
  total      = per length × per width × per height

Answer = the orientation with the highest total

Only whole cartons count, so the remainder in each direction is wasted space. That is why a carton one centimeter too long can cost you an entire column.

Geometric fit versus what actually loads

The number above is a geometric fit: perfect cartons, perfectly stacked, no bracing, no pallets. Real loading is messier, which is why forwarders quote 25 to 28 CBM for a 20 ft and 65 to 68 for a 40 ft high cube against geometric cubes of roughly 33 and 76.

If your cartons are palletized, the pallets change the arithmetic completely: you are then fitting pallets, not cartons, and the deck height eats a layer. This tool flags when a geometric fit runs past the practical CBM so the number does not mislead you.

Designing the carton around the container

Most people size a carton around the product and then find out what fits. Doing it the other way round is where the savings are.

A 20 ft container is 235 cm wide inside. A 40 cm carton gives you five across with 35 cm wasted; a 47 cm carton gives you five across with almost nothing wasted. That is the same number of cartons occupying the same floor, but each one holds 17% more product. Across a full container that is a meaningful share of your freight cost per unit.

The same logic applies to height. A 40 ft high cube is 269 cm inside, so a 53 cm carton stacks five high with 4 cm spare, while a 55 cm carton stacks four with 49 cm wasted. Two centimeters of carton height costs you an entire layer.

If you are specifying packaging for a product that will ship by sea for years, it is worth checking the container arithmetic before the carton tooling is ordered.

Common mistakes

• Using external container dimensions. The outside of a 20 ft box is 6.06 m; the inside is about 5.89 m. Loading uses the inside.
• Only trying one orientation. The gap between the best and worst orientation is often 20% or more.
• Forgetting pallets. If the cartons ship on pallets, calculate pallets per container instead.
• Ignoring payload weight. Dense cargo hits the container weight limit long before it fills the space.
• Loading to the ceiling. You need clearance to get the last layer in, and the doors are shorter than the interior.

FAQ

Rules last checked: Sep 24, 2026

Estimate only. Confirm with your carrier before booking.