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Paper Thickness Converter - GSM to Caliper (Points) & mm
Convert paper basis weight (GSM) to caliper thickness in points and millimeters, across six common stock categories, from uncoated text to coated cover.
Six stock categories, each with a real bulk factor
Results in points (thousandths of an inch) and millimeters
Typical use noted for every stock category
1
Pick your paper category
Uncoated text, coated cover, bristol, and more, each stock type compresses differently at the same weight.
2
Enter the GSM
Type the basis weight from your spec sheet or paper swatch book. The conversion runs as you type.
3
Read the caliper
Get the thickness in points and millimeters, the numbers your printer or bindery needs for cover stock, tab dividers, or packaging.
Common calipers, by stock
Typical thickness at common basis weights, the numbers to sanity check your spec sheet against.
Uncoated text / bond
| GSM | Caliper (points) |
Typical use |
|---|---|---|
| 60 gsm | 3.1 pt | Economy copy paper |
| 75 gsm | 3.8 pt | Standard office paper |
| 90 gsm | 4.6 pt | Letterhead |
| 105 gsm | 5.4 pt | Premium letterhead |
| 120 gsm | 6.1 pt | Heavy correspondence |
Coated text (gloss / matte)
| GSM | Caliper (points) |
Typical use |
|---|---|---|
| 80 gsm | 2.7 pt | Magazine pages |
| 100 gsm | 3.4 pt | Coated brochures |
| 115 gsm | 3.9 pt | Catalog covers |
| 130 gsm | 4.4 pt | Presentation folders |
| 150 gsm | 5.0 pt | Premium brochures |
Uncoated cover / bristol
| GSM | Caliper (points) |
Typical use |
|---|---|---|
| 176 gsm | 8.0 pt | Light cardstock |
| 216 gsm | 9.8 pt | Covers, postcards |
| 270 gsm | 12.2 pt | Business cards |
| 300 gsm | 13.6 pt | Premium cards |
| 352 gsm | 15.9 pt | Heavy cards, packaging |
The bulk factors behind the math
Caliper depends on basis weight and how densely each stock is pressed. These are typical industry bulk factors; a specific mill’s paper can vary.
| Paper category | Typical bulk factor | Formula |
|---|---|---|
| Uncoated text / bond | 1.30 cm³/g | mm = gsm × 1.30 ÷ 1000 |
| Coated text (gloss / matte) | 0.85 cm³/g | mm = gsm × 0.85 ÷ 1000 |
| Uncoated cover / bristol | 1.15 cm³/g | mm = gsm × 1.15 ÷ 1000 |
| Coated cover | 0.80 cm³/g | mm = gsm × 0.80 ÷ 1000 |
| Newsprint | 1.60 cm³/g | mm = gsm × 1.60 ÷ 1000 |
| Kraft / linerboard | 1.40 cm³/g | mm = gsm × 1.40 ÷ 1000 |
Worked example: 250 gsm coated cover = 250 × 0.80 ÷ 1000 = 0.2 mm, about 7.9 points, a common weight for postcards and folder covers.
What paper thickness works for what
Under 4 pt · Lightweight
Flyers, inserts, everyday prints. Flexes easily and feeds through most printers without issue.
4 to 8 pt · Medium
Brochures, letterheads, presentation sheets. Holds a fold cleanly, still runs through standard equipment.
8 to 14 pt · Heavyweight
Postcards, covers, folder stock. Stiff enough to stand up to handling and mailing.
14 pt+ · Rigid cardstock
Business cards, tags, packaging. Needs a heavier-duty press or die-cutting to work with.
Paper thickness FAQs
What is a "point" of paper thickness?
One point equals one thousandth of an inch (0.001 in). It is the standard way US printers measure caliper, separate from basis weight in GSM or pounds.
Why does the same GSM give a different caliper for different papers?
Thickness depends on both weight and density. Coated stock is pressed tighter and calendered smooth, so it comes out thinner than an uncoated sheet of the same weight. That density is what the bulk factor captures.
Is this conversion exact?
No, it is a close estimate using typical industry bulk factors for each stock category. The exact caliper varies by mill and specific paper line, so check the manufacturer's spec sheet when precision matters, like packaging that must fit a fixed slot.
What caliper is standard for business cards?
Most business cards run 14 to 18 points, roughly 300 to 400 gsm in coated or uncoated cover. Premium cards can run 24 points or more.
How does caliper affect folding and binding?
Thicker stock needs more force to fold cleanly and can crack at the spine without scoring. Above about 12 points, most print shops score before folding, and bindery equipment also has maximum caliper limits per sheet.
Can two papers with the same GSM have different thicknesses?
Yes, GSM is weight, not thickness (caliper). A bulky uncoated stock can be thicker than a dense coated one at the same GSM. When thickness matters (spine width, mailing specs), check caliper too.
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