Paperboard Caliper & Folding Allowance Guide
In packaging engineering, paperboard is not a 2D line. It has physical thickness, fiber grain, and volume. Understand caliper units, corrugated flute profiles, and how our automated 1.5 × t clearance formula guarantees flawless box closure.
What is Paperboard Caliper?
Caliper refers to the physical thickness of a sheet of paperboard, measured under standard TAPPI laboratory conditions using a precision micrometer.
North American “Point” System (pt)
In the US and Canada, caliper is measured in Points, where 1 Point equals 1/1,000th of an inch (0.001 in or 1 mil). For example, a 16pt board is 0.016 inches thick (~0.41 mm).
European & Global Metric System (mm / µm)
In Europe and metric regions, caliper is stated in millimeters (mm) or microns (µm), alongside Grammage (grams per square meter / gsm). For example, a 300 gsm folding boxboard typically has a caliper of ~0.40 mm (400 µm).
Standard Board Caliper Conversion Matrix
Use this quick conversion chart to find the exact millimeter caliper to enter into the DielineKit CAD generator.
| Point (pt) | Metric (mm) | Grammage (GSM) | Board Classification | Typical Usage |
|---|---|---|---|---|
| 12 pt | 0.30 mm | 240 gsm | SBS Cardstock | Cosmetic sample cartons, pharmaceutical inserts |
| 14 pt | 0.35 mm | 270 gsm | SBS / Kraft | Small skincare boxes, lightweight retail cartons |
| 16 pt | 0.41 mm | 310 gsm | SBS Bleached Board | Standard cosmetics, perfume cartons, confectionery |
| 18 pt | 0.46 mm | 350 gsm | Heavy SBS / CCNB | Electronics accessories, supplements, candle boxes |
| 20 pt | 0.51 mm | 380 gsm | CCNB / Kraft Paperboard | Heavy hardware, retail display cartons |
| 24 pt | 0.61 mm | 450 gsm | Heavy Folding Boxboard | Beverage packs, dense luxury cartons |
| F-Flute | 0.90 mm | 400+ gsm | Micro-Flute Corrugated | Premium compact mailers, small hardware |
| E-Flute | 1.50 mm | 500+ gsm | Fine Corrugated Board | E-commerce subscription boxes, luxury mailers |
| B-Flute | 3.00 mm | 650+ gsm | Standard Shipping Flute | Heavy shipping cartons, postal protective mailers |
The 1.5 × Caliper Clearance Formula
When paperboard is bent around a crease score, the material forms a curved hinge. The interior surface of the fold is compressed while the exterior surface is stretched.
TuckWidth = PanelLength - (2 × 1.5 × Caliper) = L - 3.0tLidDepth = Width - 0.5 × Caliper = W - 0.5tInnerWallOffset = 2.0 × Caliper + FluteCrushToleranceIf a dieline designer simply draws a tuck flap with the same width as the main panel (L), the tuck head will hit the folded side dust flaps during assembly. The carton will bulge, the tuck head will crease permanently, and retail automated packing machines will jam. DielineKit eliminates this error automatically.
Test Your Board Caliper in CAD
Select any caliper from 0.3mm to 3.0mm and watch the folding simulation adapt instantly with real-time clearance compensation.