Card Stock Weight and Size Calculator
Calculate card stock weight in GSM, points, and pounds.
Find the right thickness for invitations, business cards, and paper crafts.
Understanding card stock weight systems:
Card stock thickness is measured differently around the world, which causes endless confusion. The three main systems are GSM (grams per square meter), points (thousandths of an inch), and US pound weight (based on a ream of a specific base sheet size).
GSM (Grams per Square Meter): This is the international standard. It measures the weight of one square meter of paper in grams. Higher GSM = thicker, heavier paper. Regular copy paper is 75–90 GSM. Card stock starts at about 160 GSM.
US Pound Weight (Cover vs. Text): The US system is confusing because the base sheet size differs between “cover” stock and “text” stock. An 80 lb cover stock is much thicker than 80 lb text stock.
Conversion: Cover lb = GSM / 2.708. Text lb = GSM / 1.48.
Points (pt): One point is 1/1000 of an inch (0.001 in, or 0.0254 mm). A 12 pt card is 0.012 inches thick. This is the only one of the three that measures thickness directly, which is why printers quote it.
Converting GSM to points needs one extra fact, and it is the fact everybody skips: weight and thickness are only related through density. A sheet of paper is mostly air, and how much air depends on how hard it was pressed.
thickness (mm) = GSM / (1000 × density in g/cm³)
points = thickness (mm) / 0.0254
Uncoated card stock runs about 0.78 g/cm³, which gives the working shortcut:
points ≈ GSM / 20
So 270 GSM lands near 13.5 pt. Watch out for conversions that put it at 23 pt instead. That answer implies a density around 0.45, which is blotting paper, not card. If a chart hands you a points figure and the matching thickness is nearly double what your calipers say, this is why.
Coated and calendered stocks are pressed denser, up to about 1.0 g/cm³, so a glossy 300 GSM sheet is genuinely thinner than an uncoated 300 GSM sheet. Same weight, less air.
Reference table, common card stock uses:
| Use | GSM | Cover lb | Points | Thickness |
|---|---|---|---|---|
| Flyers, inserts | 160–180 | 59–66 lb | 8–9 pt | 0.21–0.23 mm |
| Postcards | 200–250 | 74–92 lb | 10–13 pt | 0.26–0.32 mm |
| Invitations | 250–300 | 92–111 lb | 13–15 pt | 0.32–0.38 mm |
| Business cards | 300–400 | 111–148 lb | 15–20 pt | 0.38–0.51 mm |
| Premium packaging | 350–450 | 129–166 lb | 18–23 pt | 0.45–0.58 mm |
Worked example: You want to print wedding invitations on 270 GSM stock.
- Cover weight: 270 / 2.708 = about 100 lb cover
- Thickness: 270 / (1000 × 0.78) = 0.346 mm
- Points: 0.346 / 0.0254 = about 14 pt
- That sits squarely in the invitation band: sturdy enough to feel expensive, still thin enough to score and fold without cracking.
Standard card stock sheet sizes:
- US Letter: 8.5 × 11 in (216 × 279 mm)
- A4: 8.27 × 11.69 in (210 × 297 mm)
- A5 (half-fold card): 5.83 × 8.27 in (148 × 210 mm)
- 12 × 12 in scrapbook: 305 × 305 mm
Tip: When choosing stock for a folding card, stay at or below 270 GSM. Heavier stock cracks when folded unless you score it first.
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This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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