Paper Weight Calculator
Enter the grammage (GSM), paper size, and number of sheets to find the total weight of your stack. Switch to basis weight mode to convert between US pound ratings and metric GSM across five standard US stock types: bond, text, cover, index and tag. All calculations update instantly as you type.
What is paper grammage (GSM)?
GSM stands for grams per square metre and is the international standard for specifying paper weight. It measures how many grams a square metre of the paper weighs, regardless of the paper size, format or intended use. A higher GSM means a heavier, thicker, and generally more durable sheet. Standard office copy paper is 80 g/m², premium writing paper runs from 90 to 120 g/m², and cardstock used for business cards or book covers typically falls between 270 and 400 g/m².
How US basis weight works and why it is confusing
The United States uses a pound-based system where paper weight is measured on a "parent sheet" - a large uncut sheet of a defined size. The trouble is that the parent sheet size differs for each paper category. Bond/writing paper is measured on a 17 x 22 inch parent sheet, text/book paper on 25 x 38 inches, and cover stock on 20 x 26 inches. Because the parent sheets have different areas, the same physical paper carries different pound ratings depending on the category. A 20 lb bond sheet and a 50 lb text sheet are identical in weight - both are 75 g/m². This is why specifying GSM removes all ambiguity when ordering from international suppliers or comparing across stock types.
How to calculate the total weight of a paper stack
The formula is straightforward: weight per sheet (grams) = sheet area (m²) × grammage (g/m²), and total weight = weight per sheet × quantity. For an A4 sheet (0.210 m × 0.297 m = 0.06237 m²) at 80 g/m², each sheet weighs 0.06237 × 80 = 4.99 g. A standard ream of 500 sheets therefore weighs 500 × 4.99 = 2495 g, or about 2.5 kg (5.5 lbs). This is why a ream of standard 80 g/m² A4 paper always weighs approximately 2.5 kg regardless of the brand.
Choosing the right paper weight for your project
The ideal grammage depends on the end use. Everyday printing and copying suits 75 to 90 g/m². Letterheads, formal correspondence, and premium inkjet printing benefit from 90 to 120 g/m² paper that feels more substantial and holds ink cleanly. Marketing brochures and flyers often use 130 to 170 g/m² text stock. Menus, postcards, and covers that need to survive repeated handling call for 250 to 350 g/m² cover stock. For anything that needs to be stiff and rigid, such as business cards or packaging, 350 to 400 g/m² is the practical minimum. When in doubt, order samples before committing to a large print run.
Common paper weights and typical uses
| Grammage (g/m²) | Typical US bond weight | Typical US text weight | Typical US cover weight | Typical use |
|---|---|---|---|---|
| 45 | 12 lb | 30 lb | n/a | Newsprint, tracing paper |
| 60 | 16 lb | 40 lb | 22 lb | Thin bond, airmail paper |
| 75 | 20 lb | 50 lb | 28 lb | Standard copy/laser paper |
| 90 | 24 lb | 60 lb | 33 lb | Premium copy, inkjet paper |
| 105 | 28 lb | 70 lb | 39 lb | Letterhead, writing paper |
| 120 | 32 lb | 80 lb | 44 lb | High-quality brochure text |
| 160 | 43 lb | 107 lb | 60 lb | Light card, poster stock |
| 200 | 53 lb | 134 lb | 74 lb | Card, light cover stock |
| 270 | 72 lb | 181 lb | 100 lb | Business cards, cover stock |
| 350 | 93 lb | 235 lb | 130 lb | Heavy cardstock, book covers |
GSM values are universal. US basis weights vary by stock category: bond, text or cover ratings are NOT directly comparable - a 20 lb bond and a 50 lb text paper are the same physical sheet (75 g/m²).
Frequently asked questions
What does 80 gsm paper mean?
80 g/m² means that each square metre of the paper weighs 80 grams. It is the most common weight for everyday office copying and printing. A single A4 sheet at 80 g/m² weighs approximately 5 grams, and a standard ream of 500 sheets weighs about 2.5 kg.
Is 20 lb bond the same as 80 gsm?
No. 20 lb bond paper is 75 g/m², not 80 g/m². Bond weight is measured on a 17 x 22 inch parent sheet, so 20 lbs on that parent sheet area converts to about 75 g/m² using the bond conversion factor of 3.76. A close match for 80 g/m² in bond weight is approximately 21 lb bond.
Why does a 60 lb text paper feel lighter than 60 lb cover paper?
Because they are measured on different parent sheets. Text weight is measured on a 25 x 38 inch sheet (large area), so 60 lb text works out to about 89 g/m². Cover weight is measured on a 20 x 26 inch sheet (smaller area), so 60 lb cover is around 163 g/m² - almost twice as heavy in metric terms. The pound numbers are not comparable across stock types.
How much does a ream of A4 paper weigh?
A standard ream of 500 sheets of 80 g/m² A4 paper weighs approximately 2.5 kg (5.5 lbs). An A4 sheet is 0.210 m x 0.297 m = 0.06237 m². At 80 g/m², each sheet is 0.06237 x 80 = 4.99 g, so 500 sheets come to 2495 g, or just under 2.5 kg.
What is the difference between paper weight and paper thickness (caliper)?
Paper weight (GSM) measures mass per area, while caliper measures physical thickness in micrometres or thousandths of an inch (mils). They are related but not the same because paper density varies by manufacturing process, coating and fibre type. A coated paper may be thinner but denser than an uncoated sheet of the same GSM. For projects where thickness matters (card slots, rigid folders), check the caliper specification alongside the GSM rating.
What paper weight should I use for business cards?
Business cards typically use 270 to 400 g/m² (100 lb cover and above). This gives the card enough rigidity to avoid bending in a wallet or during handling. Luxury business cards often go up to 600 g/m² when printed on duplex (two layers bonded together) stock. Anything below 250 g/m² will feel flimsy as a business card.