Oct 13, 2026Help Center
Paper Weight Explained: GSM, PT and LB (With Quick Conversions)
GSM, points and basis weight measure the same paper three different ways. A plain-English guide with quick conversions for common packaging boards.
Three systems, one sheet of paper
Paper weight confuses buyers because the packaging world uses three different systems side by side: GSM (metric), points or PT (US thousandths of an inch), and pounds or LB (US basis weight). They all describe the same thing - how heavy the sheet is - just in different units.
What GSM means
GSM stands for grams per square meter. It is the weight of one square meter of the sheet. Higher GSM means thicker, stiffer board. GSM is the most universal unit in packaging because it works for every paper and board type without per-size conversion tables.
What PT (points) means
A point is one thousandth of an inch, and it describes caliper - the actual thickness of the sheet. You will see PT used for US-style cover boards: 12 pt, 14 pt, 16 pt, 18 pt and up. Two boards with the same GSM can have slightly different PT because coating and density affect thickness.
What LB means
Basis weight in pounds comes from the US paper trade: it is the weight in pounds of a ream (usually 500 sheets) of the paper at its standard basic size. The confusing part is that the basic size differs between paper categories - a 100 lb cover is not the same sheet as a 100 lb text. That is why LB alone is ambiguous and GSM is clearer.
Common conversions for packaging buyers
- 250 gsm is roughly 92 lb cover, around 14 pt caliper - light folding carton territory
- 300 gsm is roughly 110 lb cover, around 17 pt caliper - standard folding carton, the board behind most custom pizza boxes and cosmetic cartons
- 350 gsm is roughly 129 lb cover, around 19-20 pt caliper - premium carton and light rigid work
- 400 gsm and above moves into rigid box and specialty board territory
Rule of thumb for quick mental math: divide PT by 2 to get an approximate GSM, and multiply GSM by 0.0022 to approximate LB cover.
Which weight for which packaging
- Light retail cartons and sleeves: 250-300 gsm
- Standard product boxes for cosmetics and supplements: 300-350 gsm
- Premium cartons with foil or heavy coverage: 350-400 gsm
- Luxury paper shopping bags and rigid gift boxes: 400 gsm sheets or greyboard wrapped in printed paper
The takeaway
When one printer quotes "350 gsm" and another says "20 pt", they may be offering very similar boards. Ask for GSM in every quote so you can compare like with like - and request a paper swatch or sample before committing. The same logic applies when comparing kraft merchandise bags quoted by different suppliers.
Unsure which weight suits your product? Tell us what you are packing and we will recommend a board weight with a physical sample to back it up.