3 Ply vs 5 Ply vs 7 Ply Box: Thickness and Which One to Use

“5 ply box thickness”, “7 ply corrugated box thickness in mm”, “is corrugated cardboard strong”: if you ship in boxes, ply is the first choice you make. More ply means more strength, but also more weight and cost.

What “ply” means

Ply is the number of paper layers in the board. A 3 ply board has two flat liners with one fluted (wavy) layer between them. A 5 ply board has two fluted layers, and a 7 ply board has three. The fluted layers give the box its cushioning and stacking strength.

Ply, thickness and strength at a glance

Ply	Approx. thickness	Typical load	Use for
3 ply (single wall)	3–4 mm	Light, a few kg	Clothing in boxes, cosmetics, light accessories, inner boxes
5 ply (double wall)	6–8 mm	Up to about 20 kg	Most ecommerce parcels, fragile items, glass, electronics, kitchenware
7 ply (triple wall)	10–12 mm	Heavy, 40 kg and above	Heavy goods, machinery parts, export and B2B cartons, stacking

These are typical ranges. The same ply can be thicker or thinner depending on the flute (B, C or E flute) and stronger or weaker depending on the paper grade (GSM and bursting factor). Ask the supplier for the board spec if strength matters.

Which ply for your products

• Light, non-fragile items under 1–2 kg: 3 ply is fine. Or skip the box and use a polybag.
• Fragile items like glass, ceramics, perfumes or electronics: 5 ply with 2 inches of cushioning on every side.
• Heavy items or parcels that will be stacked in a truck: 5 ply for moderate weight, 7 ply for heavy.
• Long, narrow items: 5 ply, because thin boxes bend in the middle.

Is corrugated cardboard strong enough?

Yes, for most shipping, if you pick the right ply and size. Corrugated boxes fail when they're too big (the product moves and hits the walls), too weak for the weight, or damp. Use a box only slightly bigger than the product plus cushioning, seal all joins with tape, and keep boxes stored dry.

Ply and shipping cost

A 7 ply box weighs noticeably more than a 3 ply box of the same size. On a light product, that extra weight can push the parcel into a higher shipping slab. And couriers charge on volumetric weight, so the box size matters even more than the ply. Check with the volumetric weight calculator and the CFT calculator for cartons.

GST on corrugated boxes

Corrugated boxes and cartons are taxed at 5% GST under HSN 4819 10. See packaging material GST rates for the full list.

For fragile items, read how to reduce product damage in shipping.