How do I pick a tier from a plastic box size chart?

Answer: Size the cavity to the longest item, then step up a tier; a 500 mm rod needs the 45 litre cavity.

Is a cavity 3 mm off nominal a reject?

Answer: Only if the drawing says so; moulded cavities run plus 2 minus 1 mm, so 444 to 447 passes.

How do I check equal outer size with unequal cavities?

Answer: Gauge the cavity at mouth and base, then rim flange and radius; an 8 mm gap comes from wall and ribs.

Can 600x400 and 400x300 boxes stack together?

Answer: Not directly; mismatched bases load off-centre, so keep them in separate zones.

Is a 2.5 mm box safe at six layers?

Answer: At room temperature with 30 kg or less, yes; at 40 C hold to five.

Plastic Box Size Chart: Specs, Materials and Selection

Quick answer: Read a plastic box size chart in three passes: inner size decides what fits, outer size what it clears, wall and material the stack.

Reading the plastic box size chart by capacity tier
Usable space and liner losses
Two standard footprints
Wall thickness, load and stack height
Materials and a three-step routine
FAQ

1. Reading the plastic box size chart by capacity tier

The first column of a plastic box size chart is capacity, not part number, and 5, 12, 25, 45, 75 and 120 litres cover most orders.

The gap is not wall thickness alone. Per side it runs 10 to 16 mm: a 1.2 to 5.0 mm wall, 4 to 6 mm of ribbing, draft and rim flange, so two 25 litre boxes can share an outer size and differ by 8 mm inside. A 20 ft unit at 2350 mm takes the 470 mm box five abreast.

Tier	Outer LxWxH (mm)	Inner LxWxH (mm)	Weight (kg)
5L	282x202x132	260x180x110	0.42
12L	374x274x164	350x250x140	0.78
25L	470x340x205	445x315x180	1.35
45L	572x412x242	545x385x215	2.10
75L	674x484x284	645x455x255	3.20
120L	782x562x336	750x530x305	4.60

2. Usable space and liner losses

Inner size means three numbers on any plastic box size chart: length and width across the mouth, depth from floor to rim, R8 to R15 corners excluded. A 445x315 cavity has a 545 mm diagonal.

Plastic box size chart guide: a black hard case open on a wooden bench, die-cut foam holding pliers and tweezers, a spare foam sheet

A liner takes back more: 20 mm per side and 15 mm on top shrink a 445x315x180 cavity to 405x275x140, cutting usable volume from 25.2 to 15.6 litres.

Dividers cost space too: three 2 mm boards take 10 mm per compartment.

3. Two standard footprints

Logistics works from footprint, not capacity. The 600x400 and 400x300 bases come from the European tote system; height is free in 120, 175, 220 and 280 mm steps.

Series	Heights (mm)	Load (kg)	Layers	Per pallet
600x400	120, 175, 220, 280	25	6	4
400x300	90, 120, 150, 180	15	8	10
800x600	150, 220, 280	30	4	2

A nominal 600x400 carries an 8 or 12 mm rim flange, and only the bottom layer takes load: six layers of 25 kg load the base with 150 kg.

4. Wall thickness, load and stack height

Wall thickness is the first variable in a plastic box size chart, not the only one: at 2.5 mm a ribbed base carries 30 kg, a flat base 18 kg.

Plastic box size chart reference: an open black case on a grey studio backdrop, empty cavity with base ribs, a foam insert in front

Stack height is set by the bottom layer: 30 kg over six layers puts 180 kg on the base, and a 2.5 mm floor creeps at 25 C, sagging 2 to 3 mm in three months. At 40 C rate a PP box at 70 percent of that load.

Wall (mm)	Load (kg)	Layers	Drop (m)	Typical use
1.2	8	3	0.8	Light parts, one-way
1.8	15	5	1.0	Sorting bins
2.5	30	6	1.2	Workshop use
3.5	60	5	1.5	Cold chain
5.0	120	4	1.8	Export packing

5. Materials and a three-step routine

PP is the workhorse: chemical resistant and cheap. HDPE suits cold stores, ABS gives stiffness, PC is clear where inspection matters, though it runs 25 to 35 percent heavier.

Material	Temp (C)	Brittle (C)	Impact (kJ/m2)	Clarity	Cost
PP	-10 to 100	-20	6	Translucent	1.0
HDPE	-30 to 80	-40	9	Opaque	1.1
ABS	-20 to 85	-25	12	Opaque	1.6
PC	-40 to 120	-50	35	Clear	3.2

The routine runs one way: cavity for the longest item plus 10 to 20 mm per side, then wall and material, then footprint against the pallet and van width.

Conclusion

Six tiers, three tables and one routine make a plastic box size chart you can quote from: cavity decides what goes in, outer size what it clears, wall and material the stack.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.