Paper Caliper
Paper Weight & Grammage · 7 specs
Direct Answer
Paper Caliper (measured in Points / pt / mils / microns, standardized under TAPPI T 411 and ISO 534) is the direct measurement of paper thickness using a precision motorized micrometer under standardized mechanical pressure. In North American commercial packaging and business card production, 1 Point equals one-thousandth of an inch (0.001 in / 25.4 µm).
Source: TAPPI T 411 (Thickness of paper, paperboard, and combined board) / ISO 534 (Determination of thickness, density and specific volume) · Last reviewed Aug 28, 2026
Specs
| Standard Point Definition | 1 Point (pt) = 0.001 inch = 1 mil = 25.4 micrometers (µm) |
| Standard 20 lb Copy Paper Caliper | Approx. 3.8 to 4.0 pt (0.004 in / ~100 µm) |
| Standard Book Paper Caliper (50 lb Text) | Approx. 4.5 to 5.2 pt (High-bulk paper reaches 5.5+ pt) |
| Paperback Book Cover (C1S) | 10 pt to 12 pt (0.010 to 0.012 in / 254 to 305 µm) |
| Standard US Postal Postcard Minimum | 7.0 pt (0.007 in / 178 µm — USPS minimum thickness to machine-sort) |
| Standard Commercial Business Card | 14 pt to 16 pt (0.014 to 0.016 in / 355 to 406 µm) |
| Ultra-Luxury Edge-Painted Business Card | 32 pt to 36 pt (0.032 to 0.036 in / ~800 to 900 µm — double-thick duplexed stock) |
Caliper vs Weight: The 'Paper Bulk' Factor
Two papers with identical GSM weight can have vastly different physical thicknesses due to fiber compression (caliper). 'High-bulk' book papers are lightly pressed during papermaking, trapping air pockets between fibers to make a 200-page book feel like a thick 350-page novel. Conversely, high-gloss coated art paper is heavily calendared between steel rollers, producing a dense, thin sheet with low caliper despite high GSM weight.
USPS Minimum Postcard Thickness Rule
The United States Postal Service (USPS Domestic Mail Manual §201) mandates that all commercial postcards must be at least 0.007 inches (7 points / 0.178 mm) thick to travel through high-speed automated sorting machines without jamming. Mailing postcards on sub-7pt cardstock incurs heavy non-machinable surcharges or return.