Card caliper and thickness

Updated 2026-10-12

When you hold a printed card, the physical depth you feel is its caliper. In the printing industry, this is distinct from the paper weight (GSM) or the sheet weight (lb). Understanding this distinction is critical when designing for specific applications, such as ID cards, business cards, or rigid packaging, because the thickness directly affects how the card fits into wallets, card holders, and automated dispensers.

GSM vs. Point vs. Caliper

It is a common misconception that paper weight directly equals thickness. While they are correlated, they are not identical.

• GSM (Grams per Square Metre): This is an absolute area weight defined by ISO 536. It tells you how much the paper weighs, not how thick it is.
• Point (pt): A paper-trade unit of thickness — 1 point is exactly 1/1000 inch (0.001 in = 0.0254 mm = 25.4 µm). This is not the same “point” used for type sizes (the typographic point is 1/72 inch), so “16 pt card” and “12 pt text” measure different things.
• Caliper: This is the actual measured distance from one surface of the card to the other, typically measured in microns (µm) or millimeters.

Two papers can have the same GSM but different calipers because they have different densities (“bulk”). A dense, coated sheet of 300 GSM is typically thinner than a bulky, uncoated 300 GSM sheet. (Basis weight — lb — is a different system again: it is a weight, not a density.)

pt and GSM are not interchangeable. pt converts exactly to thickness units — mm (× 0.0254) and microns (× 25.4) — because both measure depth. GSM is a weight per area, so it relates to thickness only through the stock’s density: caliper (mm) ≈ GSM × bulk ÷ 1000. Bulk (cm³/g) varies by mill — measured production art card runs about 1.2–1.3 — so the same 300 GSM can measure 0.30 mm in one mill’s dense stock and 0.39 mm in another’s. That is why a 300 GSM art card from one manufacturer can be thicker than a 310 GSM from another.

Measuring Card Thickness

To verify the thickness of a finished card, you use a digital or dial caliper. Here is how to measure it accurately:

1. Select a Sample: Do not measure a card from the very edge of a ream, as the edges may be compressed or uneven. Select a card from the middle of the stack.
2. Position the Caliper: Place the card between the anvil and the jaw of the caliper. Ensure the card is flat and perpendicular to the measuring face.
3. Read the Value: Look at the display. Measured art card business cards run 0.30–0.47 mm (about 12–18 pt) across the 250–360 gsm range — 400 gsm heavy stock reaches 0.54–0.57 mm (21–22 pt); PVC ID-1 cards are 0.76 mm.

Typical Thickness Ranges

The following table illustrates the approximate caliper for common card stocks. Note that these values can vary slightly based on the paper’s density and finish (lamination adds significant thickness). For our caliper-measured figures of production art card — and how we take them — see card stock measurements.

Why Caliper Matters for Design

If you are designing a card that must fit into a specific slot, such as a hotel key card holder or a credit card pocket, the final caliper is the only number that matters. Lamination films, typically 24–27 microns thick per side (30–35 microns for soft-touch), will increase the total thickness. If your design includes a spot UV or foil stamp, these processes generally do not change the caliper significantly, but embossing or debossing will alter the surface profile, potentially affecting how the card feels and how it stacks.

Always request a physical proof before committing to a large run if the card has a specific dimensional requirement.

FAQ

Can I calculate thickness directly from GSM? No — you can only estimate it. Thickness depends on the stock’s density, and you cannot derive an exact caliper from weight alone: caliper (mm) ≈ GSM × bulk ÷ 1000, where bulk (cm³/g) varies by paper type and manufacturer. (pt → mm, by contrast, is exact: 1 pt = 0.0254 mm.) For precise dimensions, you must measure the physical sample.

How much does lamination increase card thickness? Standard lamination films are typically 24–27 microns (0.024–0.027 mm) thick per side — 30–35 microns for soft-touch. Applied to both sides, a 310 GSM card (≈0.38–0.40 mm) with 25-micron film becomes ≈0.43–0.45 mm.

What is the standard thickness for ID-1 cards? According to ISO/IEC 7810, the standard ID-1 card (credit card size) has a thickness of 0.76 mm ± 0.08 mm. This is significantly thicker than standard paper business cards, which is why they are usually made from PVC or PET rather than paper.