Paper weight tells you how heavy a sheet is, and paper size tells you its length and width. Weight is shown in gsm or in pounds, size is usually Letter or the A series, and both need to fit what your printer accepts. This guide defines each term with simple examples.
Weight in Plain Terms
Two systems are in common use, and they do not use the same scale, so the same paper can show two different numbers.
- gsm means grams per square meter. It measures the weight of one square meter of the paper, so a higher number means a thicker, stiffer sheet. It is used almost everywhere outside North America.
- Pounds (lb) is the older North American system. It is based on the weight of a stack of uncut sheets at a basic size, which is why the same paper can show a different number from its gsm value.
As a loose guide, light sheets feel like newsprint or copy paper, medium sheets feel like a letterhead, and heavy sheets feel like a postcard. Exact limits differ by printer, so check the maker’s guide.
Common Sizes You Will Meet
| Size | Where it is used | Typical use |
|---|---|---|
| Letter | North America | Office documents, school work |
| Legal | North America | Longer forms and contracts |
| A4 | Most other regions | Office documents, letters |
| A5 | Most other regions | Notes, small booklets |
| 4 x 6 inch | Worldwide | Small photo prints, labels |
Letter and A4 are close but not identical. A4 is a little narrower and a little longer, so a page set up for one may be scaled or trimmed when printed on the other.
Matching Both to Your Printer
- Open the printer manual and find the table of supported sizes and weights.
- Note the heaviest and lightest sheet the main tray accepts, since a rear or manual slot may allow more.
- Check the weight printed on the pack and compare it with the manual, using the packaging if it lists both gsm and pounds.
- Set the same size in the tray settings, the print dialog and your document.
- Load one sheet first when trying a new weight, and watch how it feeds.
FAQ
Is a higher gsm always a better sheet?
Not necessarily. Higher means heavier and stiffer, which suits covers and cards, but ordinary letters work well on lighter sheets and many printers feed those more reliably.
What happens if my document size does not match the paper?
The printer may scale the page, trim the edges or stop and ask for the right sheet. Setting the size in the document and the print dialog avoids most surprises.
The Short Version
Weight is gsm or pounds, and size is a width and length such as Letter or A4. Read the limits in your printer guide, then set the same size everywhere before you print.