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Paper Weight Calculator
Convert paper weight between GSM, bond weight, text weight, and cover weight to find the right paper stock for any printing or crafting project.
Calculator
Formula
GSM stands for grams per square meter and is the universal paper weight standard. Basis Weight is the weight in pounds of 500 sheets (one ream) of paper cut to its standard basis size. The basis size varies by paper type: Bond/Writing uses 17×22 in (374 in²), Text/Book uses 25×38 in (950 in²), and Cover uses 20×26 in (520 in²). The constant 1406.5 converts from pounds-per-ream to grams per square meter.
Source: TAPPI (Technical Association of the Pulp and Paper Industry) — Paper Basis Weight Standards
How it works
Paper weight is expressed differently depending on where you are in the world. In most countries, paper is measured in GSM — grams per square meter — which is a direct, absolute measurement of how heavy one square meter of the paper would be. A higher GSM means a thicker, heavier sheet. Common office copy paper is around 75–80 GSM, while a heavy cardstock might be 300 GSM or more.
In the United States, paper weight is stated as a "basis weight" in pounds — but here's the catch: that number refers to the weight of 500 sheets (one ream) cut to a specific "parent" or "basis" size that varies by paper type. Bond paper uses a 17×22 inch parent size, text paper uses 25×38 inches, and cover stock uses 20×26 inches. This is why a 20 lb bond sheet and a 50 lb text sheet can feel nearly identical in thickness — they're both approximately 75 GSM, just measured against different parent sheet sizes. To convert any basis weight to GSM, multiply the basis weight by 1,406.5 and divide by the basis size in square inches.
This calculator handles six common paper categories: Bond/Writing (used for letterhead, copier paper, and office stationery), Text/Book (used for books, brochures, and flyers), Cover (heavy cardstock for business cards and book covers), Offset/Opaque (uncoated printing papers), Bristol (used for greeting cards and file folders), and Index (used for index cards and dividers). Knowing your GSM equivalent allows you to compare papers across these categories on an equal footing and make informed purchase decisions.
Worked example
Suppose you are a graphic designer ordering paper for a brochure and the supplier lists their stock as 80 lb text. You want to know the GSM equivalent to confirm it matches the feel you're after.
Step 1 — Identify the paper type: Text paper uses a basis size of 25×38 inches = 950 square inches.
Step 2 — Apply the formula: GSM = 80 × 1406.5 ÷ 950 = 118.4 GSM.
Step 3 — Interpret the result: At roughly 118 GSM, this paper is noticeably heavier than standard copy paper (75–80 GSM) but lighter than cardstock. It's an excellent choice for a folded brochure — sturdy enough to hold its shape without being too thick to fold cleanly.
Bonus conversion: What is the cover weight equivalent? Cover uses 520 in² as its basis size. Cover equivalent = 118.4 × 520 ÷ 1406.5 = 43.7 lb cover. This means 80 lb text and 43.7 lb cover are the same physical paper — a comparison that would be impossible to make from the basis weights alone without this conversion.
Limitations & notes
This calculator uses the standard TAPPI basis sizes for each paper category. Some specialty papers — such as newsprint, kraft, and writing tablet papers — may use non-standard parent sizes and will not convert accurately with these formulas. Thickness estimates are approximate and assume a typical paper density of 1.2 g/cm³; coated papers (which use clay-based coatings) will be slightly thinner at the same GSM than uncoated papers because the coating is denser. Additionally, the US basis weight system is inherently confusing because different trade channels sometimes use different category labels for the same sheet, so always confirm the paper category with your supplier before placing a large order.
Frequently asked questions
What does GSM mean for paper?
GSM stands for grams per square meter. It is the internationally recognised measurement of paper weight, representing how many grams a single sheet measuring one square meter would weigh. The higher the GSM, the heavier and generally thicker the paper. Standard copy paper is 75–80 GSM, while thick cardstock can be 300 GSM or above.
Why does 20 lb bond feel the same as 50 lb text?
Because they are measured against different parent sheet sizes. Bond basis weight is calculated from a 17×22 inch sheet, while text basis weight uses a 25×38 inch sheet — more than 2.5 times larger. When you account for those different reference sizes, 20 lb bond and 50 lb text both convert to approximately 75 GSM, which is why they feel virtually identical in your hands.
What paper weight should I use for business cards?
Business cards are typically printed on cover stock in the range of 14–16 lb cover, which is equivalent to roughly 378–432 GSM. Many premium business cards use 16 pt or 18 pt cardstock, where 'pt' refers to thickness in thousandths of an inch rather than weight, but these generally correspond to heavy cover weights. A minimum of 300 GSM is recommended for a professional, rigid feel.
What is the difference between text weight and cover weight paper?
Text weight paper is lighter and more flexible, typically in the 60–120 GSM range, and is used for the body pages of books, flyers, and brochures. Cover weight paper is heavier and stiffer, typically 160–350 GSM, and is used for covers, business cards, and postcards. Because they use different basis sizes, you cannot compare their pound values directly — always convert to GSM for an accurate comparison.
How do I know what paper weight to use for printing?
For everyday office printing and copying, 75–90 GSM bond paper is standard. For marketing flyers and brochures, 100–150 GSM text or offset paper gives a professional feel. For posters, use 170–200 GSM. For business cards and heavy covers, choose 250–350 GSM cardstock. Most home and office inkjet printers handle up to about 220 GSM; anything heavier typically requires a commercial printer.
Last updated: 2025-01-15 · Formula verified against primary sources.