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Paper Weight Converter

Convert paper GSM to lb basis weight, by paper type

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Pick the direction — lb → gsm or gsm → lb — with the toggle.
  2. 2.Type the paper weight into the value field.
  3. 3.Choose the paper type (bond, text, cover, index, tag or bristol) and read the converted result instantly; tick 'Compare across all paper types' to see every stock at once.

About Paper Weight Converter

This paper weight converter turns paper weight between GSM (grams per square meter) and the US pound (lb) basis weight, and the one setting you must get right is the paper type, because a pound of one stock is not a pound of another. Choose a direction, enter a number, pick the paper type, and the result appears instantly and entirely in your browser.

GSM is the simple, international unit: it is the weight in grams of one square meter of the paper, using the same fixed one-square-meter reference for every stock. That makes GSM directly comparable across bond, text, cover and everything else — a higher GSM is always heavier paper. Because the reference never changes, GSM needs no paper-type setting at all.

The US pound basis weight is where it gets confusing. In the American system a paper's weight in pounds is the total weight of one ream (500 sheets) cut to that grade's basis size — the standard parent-sheet dimensions defined for that category. The catch is that each grade uses a different basis size: Bond, Writing and Ledger use 17×22 inches; Text, Book and Offset use 25×38 inches; Cover uses 20×26 inches; Index uses 25.5×30.5 inches; Tag uses 24×36 inches; and Bristol uses 22.5×28.5 inches. Because the sheet you weigh is a different size for each grade, the same '100 lb' means very different actual paper. 100 lb text is about 148 gsm, while 100 lb cover is about 270 gsm — nearly double the thickness for the identical pound number. That is exactly why '80 lb' cardstock and '80 lb' book paper feel nothing alike, and why you must select the paper type before converting.

Under the hood each grade has its own conversion factor (gsm = lb × factor) derived from its basis size: bond ≈ 3.76, text ≈ 1.48, cover ≈ 2.70, index ≈ 1.81, tag ≈ 1.63 and bristol ≈ 2.19. Handy checkpoints: 20 lb bond ≈ 75 gsm, 24 lb bond ≈ 90 gsm, 70 lb text ≈ 104 gsm, 80 lb text ≈ 118 gsm, 65 lb cover ≈ 176 gsm, 80 lb cover ≈ 216 gsm, 100 lb cover ≈ 270 gsm and 90 lb index ≈ 163 gsm. Different printers round the underlying constants slightly differently, so an answer may land a gram either side of another chart, but to the nearest whole gsm the results agree.

Use 'Compare across all paper types' to see one weight expressed for every stock at once — the fastest way to see how far apart the grades really are. Everything runs client-side, so nothing you type is ever uploaded.

Frequently asked questions

Why do I have to choose a paper type to convert?
Because the US pound weight depends on the grade. A paper's pound rating is the weight of 500 sheets cut to that grade's basis size, and each grade uses a different basis size (bond 17×22 in, text 25×38 in, cover 20×26 in, and so on). So the same pound number maps to a different gsm for each type. GSM itself is grade-independent, but to translate to or from pounds the tool needs to know which stock you mean.
How do I convert gsm to lbs for paper?
Select 'gsm → lb', enter the grammage, and pick the paper type. The tool divides by that grade's factor (gsm per lb): text ≈ 1.48, cover ≈ 2.70, bond ≈ 3.76, index ≈ 1.81. For example 216 gsm ÷ 2.70 ≈ 80 lb cover, while 104 gsm ÷ 1.48 ≈ 70 lb text.
Why is 100 lb cover so much heavier than 100 lb text?
They are measured on different basis sizes. 100 lb text is 500 sheets of 25×38 in (about 148 gsm), while 100 lb cover is 500 sheets of the smaller 20×26 in (about 270 gsm). Cover sheets are smaller, so reaching the same total ream weight takes much heavier, thicker paper — nearly double the gsm for the identical pound label.
What is 80 lb paper in gsm?
It depends entirely on the type. 80 lb text/book ≈ 118 gsm, 80 lb cover ≈ 216 gsm, and 80 lb index ≈ 145 gsm. The '80 lb cardstock' people usually mean is 80 lb cover ≈ 216 gsm. Always pair the pound number with its grade, or the answer can be off by nearly double.
Are these conversions exact?
They are accurate to the nearest gram. Each factor is computed from the grade's basis size using 1 in² = 0.00064516 m² and 1 lb = 453.59237 g, then gsm = lb × factor. Different suppliers round the constants slightly, so a value can differ by about a gram between charts, but rounded to whole gsm the results match standard printing conversion tables.

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