How much clearance should a protective case size range leave?

Answer: 4 to 6 mm per side for one item, 2 to 5 mm top and bottom, taken up by foam preload.

Is foam thickness inside the cavity or on top of it?

Answer: Inside. Base and lid thickness are subtracted from cavity height.

How much gap between several items in one protective case size range step?

Answer: 2 to 3 mm between units, 4 mm to the wall, dividers equal in thickness.

Should a protective case size range be checked against a pallet?

Answer: For bulk orders, yes. Cases per layer times layers gives the pallet count.

The loaded case weighs 30 kg. Does the cavity grow?

Answer: No, the carry method changes. Above 25 kg add wheels, which bring 40 to 60 mm of height.

Protective Case Size Range: How Much Clearance to Leave Inside

Quick answer: Read a protective case size range after the item is measured: 4 to 6 mm of clearance per side, foam taking 30 to 70 mm of height, and 2 to 3 mm left for lid compression. Fill the cavity from the inside out.

Working Through the Protective Case Size Range
Clearance for One Item and for Many
Foam Comes Out of the Cavity
Finger Room and Lid Compression
Working Back from Pallets and Trailer Width
FAQ

1. Working Through the Protective Case Size Range

A protective case size range is read from the item outward: longest edge, widest point and highest point, plus bosses, cables and handle overhang, plus foam. Only then take the smallest step that clears the total.

Reverse the order and the cost climbs. A case chosen first usually runs one step large, so foam grows from 25 to 50 mm, tare rises 1.8 kg and damping does not improve, since EVA past 40 mm is hard to compress evenly.

Load	Per side	Base and lid	Foam
Rigid instrument	5 to 6 mm	30 / 25 mm	30 kg/m³
Item with bosses	6 to 8 mm	30 / 30 mm	25 kg/m³
Identical units	2 to 3 mm	25 / 20 mm	10 mm dividers
Soft items	3 to 4 mm	20 / 20 mm	20 kg/m³

2. Clearance for One Item and for Many

In a protective case size range, one item takes clearance per side. Length and width get 4 to 6 mm each side, height gets 5 mm below and 2 mm above, and a boss side takes 8 mm; ten millimetres all round leaves every face loose.

Several units need dividers first: 2 to 3 mm between units, 4 mm to each wall, so six units span six widths plus five dividers plus 8 mm. Equal thickness matters, because 1 mm of variance stops the last unit seating.

3. Foam Comes Out of the Cavity

Foam is subtracted from the cavity, never added. A 25 mm base and a 20 mm lid need 45 mm above a 200 mm item, so the cavity must reach 247 mm; the nearest step is 250 mm and the spare 3 mm is compression.

Side foam sets length and width: 15 mm all round turns a 300 mm item into a 330 mm cavity, while 25 mm needs 350 mm and jumps a step. Density matters too: 30 kg/m³ EVA absorbs best at 25 percent compression, while 20 kg/m³ bottoms out early.

Foam layout	Base	Lid	Sides	Height consumed
Thin	15 mm	15 mm	10 mm	30 mm
Standard	25 mm	20 mm	15 mm	45 mm
Heavy duty	40 mm	30 mm	25 mm	70 mm

4. Finger Room and Lid Compression

Finger room comes out of the cavity: lifting an item needs a 30 mm wide, 50 mm deep notch at the slot edge, and that space is not load space. A cavity exactly as deep as an upright item leaves no grip at all.

Lid compression runs 2 to 3 mm. Under 2 mm the item keeps 1 mm of play with the lid shut; over 3 mm the latches stay preloaded and nylon catches creep above 40 degrees Celsius. Tune it with lid foam, not latch travel.

5. Working Back from Pallets and Trailer Width

Bulk orders are worked backwards from the pallet in any protective case size range. On a 1200 x 1000 mm pallet a 480 x 360 x 290 mm case lays two across and three along: six per layer, 18 in three layers, 1020 mm and 173 kg.

Trailer width comes next. At 2350 mm internal width a 1200 mm pallet sits one across and a 1000 mm pallet two, so 24 cases need 2.4 m one way and 1 m the other. Height limits layers: two 1020 mm pallets reach 2040 mm under a 2.4 m roof, a 1310 mm one goes single.

Pallet	Per layer	Layers	Per pallet	Height
1200 x 1000	6	3	18	1020 mm
1200 x 1000	6	4	24	1310 mm
1200 x 800	4	3	12	1020 mm
1100 x 1100	6	3	18	1020 mm

Conclusion

Clearance is a budget spent on foam, dividers and finger room, and it must balance. Measure the item, add the foam, reserve the compression, then take the smallest step that fits. A protective case size range is a selection method before it is a table of numbers.

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.