This paper weight calculator exists because of one genuinely confusing convention. In the United States, paper is sold by the weight of a ream of its parent sheets, and every grade of paper uses a different parent sheet size. The number on the wrapper therefore does not describe the paper on its own — it only means something once you know which grade it belongs to. Grams per square metre has no such problem, which is why the metric figure is the headline here.
Arb Digital publishes this in a free tools library aimed at getting a defensible number quickly. It converts weights in both directions, prices the physical weight of a print run for shipping, and shows what the same stock would be called under every other grade so you can compare quotes that use different vocabulary.
What This Paper Weight Calculator Does
Enter a US basis weight and a grade, and it returns the grammage in gsm plus the equivalent basis weight under every other grade. Enter a gsm figure instead and it goes the other way. In both directions it also computes the weight of a single finished sheet at whatever trim size you specify, the weight of the whole run, and — if you supply a measured caliper — how thick the stack will be.
The finished sheet size and the parent sheet size are two different things, and the tool keeps them separate. The parent size, chosen by the grade selector, is only used to interpret the pound figure. The finished size is the sheet you are actually printing, and it drives the physical weight of the job.
The boundary with the closest tool is clean. The paper size converter deals with dimensions — A4 to letter, B series, trim sizes — and says nothing about weight. This page deals with weight and says nothing about which format to print on. The printing cost calculator covers the money side of a print job rather than the physical stock.
How to Use It
- Choose the direction. Most people start from a pound figure on a wrapper or a quote and want the gsm.
- Pick the grade carefully. Bond, text, cover, index and bristol each use a different parent sheet, and picking the wrong one changes the answer by a factor of two or more.
- Enter the finished sheet size. This is the trimmed page you are printing, not the parent sheet.
- Set the run length. 500 is a ream; use the real quantity if you are estimating freight.
- Add a measured caliper if you have one. It is the only way to get stack thickness, because thickness is not derivable from weight.
The Formula: Basis Weight, Grammage and Why They Disagree
Grammage is the mass of one square metre of the paper, measured under a defined procedure — the international method is set out in ISO 536, Paper and board — Determination of grammage. It is a property of the material and does not depend on how the sheet is cut.
US basis weight is the weight in pounds of 500 sheets of the grade's parent size. Converting one to the other therefore needs the parent area:
gsm = basis weight in lb × 1,406.1 ÷ parent sheet area in square inches
The constant comes from unit arithmetic: 453.59237 grams per pound, divided by 500 sheets, divided by 0.00064516 square metres per square inch. Neenah Paper's basis weight reference lists the parent sizes used here — bond at 17 × 22 inches, text at 25 × 38, cover at 20 × 26, index at 25½ × 30½ and bristol at 22½ × 28½ — and states plainly that because the base sizes differ, the basis weights do not correspond between grades.
Worked example, which is the default on this page. 20 lb bond: the parent area is 17 × 22 = 374 square inches, so gsm = 20 × 1,406.1 ÷ 374 = 75.2 gsm. A letter-size sheet is 8.5 × 11 = 93.5 square inches, which is 0.0603 square metres, so one sheet weighs 75.2 × 0.0603 = 4.54 grams. Five hundred of them weigh 2,268 grams — 2.27 kg, or 5.0 pounds. That is the familiar five-pound ream of copier paper, and it falls straight out of the arithmetic.
Now run 50 lb text through the same formula. The parent area is 25 × 38 = 950 square inches, so gsm = 50 × 1,406.1 ÷ 950 = 74.0 gsm. Twenty-pound bond and fifty-pound text are, to within a gram per square metre, the same paper.
The 80 lb Trap
The clearest demonstration of why grade matters is the number 80, because it appears on two completely different papers. Eighty-pound text works out at 80 × 1,406.1 ÷ 950 = about 118 gsm — a good quality letterhead or brochure inner page, still clearly a sheet of paper. Eighty-pound cover works out at 80 × 1,406.1 ÷ 520 = about 216 gsm — card stock, nearly twice as heavy, used for covers and business cards.
Order the wrong one and the job is wrong in a way that cannot be fixed after printing. This is the single most common paper specification error, and it happens because the pound figure looks like a universal scale and is not. If a quote or a specification says only "80 lb", it is incomplete, and the correct response is to ask which grade before anyone orders anything.
The same trap exists at every number. Sixty-five pound cover is roughly 176 gsm while sixty-five pound text is about 96 gsm. One hundred pound cover is about 270 gsm while one hundred pound text is about 148 gsm. Whenever two figures need comparing, put both into gsm first — that is what the equivalents line under the headline result is for.
Why Thickness Is Not the Same as Weight
People often use weight as a proxy for how substantial a sheet feels, and it is only a rough one. Thickness — called caliper, and measured in thousandths of an inch, known as points — depends on the paper's bulk as well as its grammage. Bulk is how much volume a given mass of fibre occupies, and it varies enormously with the manufacturing process.
An uncoated, lightly calendered stock is fluffy: high bulk, so it is thicker than its grammage suggests. A heavily calendered gloss coated stock is compressed and dense: low bulk, thinner than its grammage suggests. Two papers at the same 250 gsm can differ in caliper by a third. This is why a book printer specifies bulk separately — it determines the spine width, and a book whose spine is wrong does not fit its cover.
Because of that, this calculator will not guess a caliper for you. It takes a measured figure from the paper's specification sheet and uses it only for the stack thickness box. Any tool that claims to convert gsm directly to points is assuming a bulk value it cannot know. If you need the underlying relationship between mass, volume and density, the density calculator handles that arithmetic in the general case.
Estimating the Weight of a Print Run for Shipping
The physical weight of a finished job is one of the more useful outputs here, because it is what freight is billed on. The arithmetic is grammage times finished sheet area times sheet count, and the tool reports it in both kilograms and pounds so it can go straight onto a carrier's form.
Two adjustments are worth making before you trust the number. First, add the packaging: cartons, wrapping and the pallet all add weight, and on a large run the pallet alone can be tens of kilograms. Second, remember that the printer buys parent sheets and trims them, so the paper consumed is larger than the paper delivered — the waste stays with the printer, but it is why the paper cost and the shipped weight do not track each other exactly.
If you are turning that shipped weight into pallets and cartons, the pallet calculator takes over from here, and the shipping cost per item calculator converts a total freight cost into a per-unit figure for pricing.
Reading a Paper Specification Without Getting Lost
A complete paper specification names four things: the grade, the weight, the finish and the size. The grade tells you which parent sheet the weight refers to. The weight tells you the grammage once you know the grade. The finish — uncoated, matte, silk, gloss — affects bulk, opacity and how ink behaves. The size is the sheet or the trim.
Two more figures appear on better specification sheets and are worth knowing about. Opacity, expressed as a percentage, tells you how much of what is printed on the reverse will show through, which matters far more than weight for double-sided work. Brightness or whiteness describes how much light the sheet reflects, which affects how colours reproduce. Neither can be inferred from grammage.
When a supplier gives you only a pound figure and no grade, treat it as an incomplete specification rather than as a number to convert. The equivalents line on this page will show you all five candidate answers at once, which is usually enough to work out from context which one they meant — but it is safer to ask.
Arb Digital's free tools library covers the sizing, weight and cost maths behind print and digital collateral, and our team is happy to talk through anything the tools cannot answer.
Browse Free Tools Talk to Arb DigitalCommon Mistakes to Avoid
- Comparing pound figures across grades — 80 lb text is about 118 gsm and 80 lb cover is about 216 gsm. The same number describes two very different papers.
- Using the finished sheet size as the parent size — basis weight is always measured at the grade's parent size, never at the trimmed page.
- Inferring caliper from grammage — bulk varies by stock, so two papers of identical weight can differ substantially in thickness.
- Forgetting packaging weight in a freight estimate — cartons and pallets are not free, and on a long run they are a meaningful share of the total.
- Accepting a specification with no grade — a pound figure alone is incomplete, and guessing is how the wrong stock gets ordered.
Related Free Tools From Arb Digital
Use the paper size converter for sheet dimensions and format conversions, the printing cost calculator for the cost of a job, the pallet calculator to palletise the finished run, the weight converter for unit changes, and the area converter when you need square metres from an unusual sheet size. Everything else is in the free online tools hub.
Frequently Asked Questions
Because each US grade weighs its ream at a different parent sheet size. Bond is weighed at 17 × 22 inches and text at 25 × 38 inches, so the same pound figure spread over a larger sheet describes a lighter paper.
Essentially yes. 20 lb bond works out at about 75 gsm and 50 lb text at about 74 gsm. They are the same material described using two different parent sheet conventions.
About 118 gsm against about 216 gsm. Text is a heavy sheet of paper; cover is card stock. Ordering one when you meant the other is the most common paper specification error there is.
Multiply the basis weight in pounds by 1,406.1 and divide by the parent sheet area in square inches for that grade. The constant comes from grams per pound, 500 sheets per ream, and square metres per square inch.
No. Thickness depends on bulk as well as mass, and bulk varies widely between coated and uncoated stocks. Take the caliper from the paper's own specification sheet and enter it here.
Because 500 letter sheets of 75 gsm paper come to about 2.27 kilograms. It is a coincidence of the letter format rather than a definition — the five-pound figure has nothing to do with the 20 lb on the wrapper.
Yes. Grammage is the mass of one square metre of the paper, expressed in grams per square metre, determined by the method in ISO 536. Unlike basis weight it does not depend on any parent sheet size.
Not necessarily. Bulk, finish and stiffness all contribute, and a high-bulk uncoated stock can feel thicker and more solid than a heavier coated one at the same grammage.
This tool performs unit arithmetic from the figures you enter. Paper specifications, tolerances and available stocks vary by mill and by region, so confirm any weight, caliper or quantity that affects an order against the supplier's own specification sheet before committing to a print run.
