How to Spec Grey Board Caliper for Rigid Boxes

Quick answer

Specify grey board by finished caliper with tolerance, not GSM alone. For rigid boxes, thickness interacts with wrap dimensions, corner geometry, stiffness, die-cut quality, and nesting clearance; a nominal board weight cannot protect those fit-critical points.

Start from the box geometry

Provide inside dimensions, finished outside dimensions, board build, lid/base clearance, corner style, and wrap construction. A change of only a few tenths of a millimeter per wall can make a telescoping lid bind or make an insert loose. Quote the caliper at the point of use.

Use caliper and tolerance

State target thickness in millimeters and the permitted range, then identify the measurement method, pressure, and conditioned state. Ask for readings across each sheet, not one center value. Tight tolerances cost more but are justified when lids, trays, or automated wrap tooling have limited clearance.

Do not ignore stiffness

Two boards at similar caliper can differ in density, ply bonding, bending stiffness, and edge quality. Specify the box load and expected stacking, then request bending or compression evidence suited to the design. Very low-density board may crush at corners even if its gauge looks correct.

Check moisture and warp

Grey board absorbs moisture and may warp before or after wrap lamination. Set moisture range and flatness expectations for the sheet size you buy. If the production site has large humidity swings, condition samples before approving die lines and lid fit.

Align die-cutting and wrapping

Board must cut cleanly without excessive dust, delamination, or exposed weak edges. Test V-grooves, corner folds, and wrapped corners on production-intent board. A board approved as a flat sample can fail when grooved or when a water-based wrap adhesive adds moisture.

Inspect each delivery

Use a defined sampling plan to check caliper, sheet size/squareness, moisture, flatness, ply separation, and corner crush. Retain an approved master panel and record lot numbers. Rejecting only after boxes are wrapped makes attribution much harder.

RFQ fields

Target caliper, tolerance, measurement method, and sheet size

Box style, load, lid/base clearance, and V-groove requirements

Density/stiffness or agreed performance requirement

Moisture, flatness, dust, and ply-bond limits

Quantity ladder; master sample; packing; destination; Incoterms

Related PackTrades Knowledge

Grey Board and Paper Board Materials Guide, Gift Boxes and Rigid Packaging Buyer Guide, Folding Carton vs Rigid Gift Box, Drawer Gift Box Sourcing Guide from China, How to Request Packaging Samples from China Factories.