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Linerboard lb per 1000 sq ft to GSM Conversion Chart

North American mills quote linerboard and medium in pounds per 1000 square feet, while much of the rest of the world uses grams per square metre. This chart converts the common corrugated weights in both directions.

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Weight (lb per 1000 sq ft)	Approx. GSM (g/m2)	Common use
23	112	Light medium (lightweight board)
26	127	Standard corrugating medium
30	146	Heavier medium, light liner
33	161	Lightweight liner, inside liner
35	171	Light liner
38	186	Standard liner, 200# board
40	195	Liner
42	205	Standard liner, 275# board
56	273	Heavy liner
69	337	Heavy duty kraft liner
90	439	Very heavy liner or chipboard
126	615	Specialty heavy sheet

Conversion factor: 1 lb per 1000 sq ft = 4.8824 g/m2. Rounded to whole gsm. Mill grade names and tolerances differ, so use the mill's own certificate for ordering.

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How to use the chart

Find your weight in lb per MSF and read the gsm value across, or search by use such as medium or kraft liner. To convert any weight not listed, multiply lb per 1000 sq ft by 4.8824 to get gsm, or divide gsm by 4.8824 to get lb per MSF. Export the table to Excel and keep it with your supplier specs so multi-country buyers speak the same units.

gsm = lb per MSF x 4.8824
lb per MSF = gsm / 4.8824
Round to whole gsm for specs
Keep both units in the item master

Why the basis weight matters

Liner and medium weight drive board price, board weight and compression strength. A 42 lb liner has about 21 percent more fibre than a 35 lb liner per square foot, which typically means higher burst and crush performance and higher cost per square metre. When comparing quotes from different regions, convert everything to one unit before comparing price per tonne or price per square metre.

Worked example

A 275# test single wall box is often built from 42 lb liners and a 26 lb medium. Converted, that is about 205 gsm liners and 127 gsm medium. With C flute take-up of about 1.43, the medium contributes roughly 127 x 1.43 = 182 gsm of paper in the board, so total board weight is about 205 + 205 + 182 = 592 gsm.

Common mistakes

Mixing lb per MSF with lb per ream or with tonnes per kilometre. Forgetting that the medium is longer than the liner because of take-up. Comparing board quotes without converting units. Add both unit fields to your ERP item master so purchasing and costing never convert by hand.

Frequently Asked Questions

How do I convert lb per 1000 sq ft to gsm?

Multiply the weight in lb per 1000 square feet by 4.8824 to get grams per square metre. For example 42 lb per MSF times 4.8824 is about 205 gsm. Round to the nearest whole number for specifications.

Is MSF the same as lb per ream?

No. A ream basis weight depends on sheet size and sheet count, while MSF is pounds per 1000 square feet. Always check which basis a quote uses before converting.

What gsm is standard corrugating medium?

A 26 lb per MSF medium is about 127 gsm and is the common standard. Light mediums of 23 lb are around 112 gsm. Mills may offer other weights, so check the current grade list.

Do all mills round to the same gsm?

No. Mills nominate their own target weights and tolerances. A 42 lb liner may be sold as 200 or 205 gsm depending on the mill. Use the mill certificate, not the chart, for contract specs.

Netray can help you keep paper grade, weight and unit of measure aligned between purchasing, costing and quality in your ERP.

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