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Which ply box do I need?

Kitne ply ka box chahiye

Over-spec wastes money. Under-spec crushes in the stack. Enter your load and how you store it, and get the cheapest board that is strong enough.

Box and load

mm
mm
mm
kg

Stacking and storage

Stack height in
boxes
Transport

Recommended board

5 ply, BC flute

150 GSM, 18 BF on all layers

Estimated box strength 234 kg against 200 kg needed. Cost about ₹16.79 per box before margin.

Get a quote for this box
Boxes in stack
6
Load on the bottom box
50.0 kg
Safety factor
× 4.0
Strength needed (BCT)
200 kg

Cheapest boards that come close

BoardEst. BCTCost/boxResult
3 ply, B flute180 GSM, 20 BF121 kg₹12.63Too weak
5 ply, BC flute120 GSM, 16 BF167 kg₹12.91Too weak
3 ply, C flute180 GSM, 20 BF143 kg₹12.96Too weak
3 ply, B flute200 GSM, 22 BF147 kg₹14.52Too weak
3 ply, C flute200 GSM, 22 BF174 kg₹14.91Too weak
3 ply, B fluteVirgin kraft, 180 GSM, 28 BF169 kg₹15.72Too weak

This is an engineering estimate (McKee formula) based on typical paper strength for each GSM and BF. Real paper varies by mill. For heavy or critical loads, confirm with a box compression test.

How it works

  1. Load on the bottom box = weight of one box × (boxes in the stack − 1).
  2. Strength needed = that load × a safety factor for storage time, humidity and transport. It usually lands between 3 and 6.
  3. Strength of each board uses the McKee formula: BCT ≈ 5.87 × ECT × √(board thickness × box perimeter). ECT (edge crush) is estimated from each paper's GSM and BF.
  4. The cheapest board that is strong enough is recommended.

Most buyers don't know the ring crush values of their paper, so this guide uses typical values per GSM and BF. Treat the answer as a starting point and confirm critical loads with a compression test.

Questions

What is the difference between 3 ply, 5 ply and 7 ply boxes?

3 ply has one fluted layer between two liners, for light goods up to about 5–7 kg. 5 ply has two fluted layers, for 10–20 kg and taller stacks. 7 ply has three, for heavy industrial loads and export.

What is BCT?

Box compression test: the load in kg a box takes from the top before it collapses. The bottom box in a stack needs a BCT several times the weight sitting on it.

Why is the safety factor so high?

Boxes lose strength over time under load, and humidity weakens paper a lot. A box that holds 400 kg on day one can hold well under half that after a month in monsoon air.

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