GSM and microns. Whatever are they?

GSM and microns. Whatever are they?

You may have heard GSM and microns banded about when people talk about print but don’t have a clue what they mean. That’s okay because today I’m going to let you in to a little secret and tell you what they mean and the difference between the two.

In Europe, paper is measured in GSM. This stands for ‘Grams per Square Metre’ and means exactly that, for example, how many grams a single sheet of paper weighs measuring 1m x 1m.

A low quality paper such as copier or inkjet paper is often 80gsm, where as a letterhead would usually be printed on either 100gsm or 120gsm. Papers weighing 130gsm to 170gsm are generally used for leaflets, flyers or posters.

200gsm to 300gsm are ideal for premium flyers or brochure covers where you want a heavier finish.

300gsm to 400gsm is ideal for business cards, post cards, presentation folders and wedding stationery as it’s very thick and has a quality feel.

Once the weight gets above 200gsm it is classified as board and this is where the term ‘microns’ comes in which indicates the thickness of the sheet. 1 micron = 1/1000 of a millimetre. 

Have a look at the table to see the equivalent weight and thickness

Board weight200gsm250gsm300gsm350gsm400gsm
Board thickness150 to 220mics190 to 285mics237 to 342mics284 to 395mics315 to 460mics

The thing that may confuse you is that different sheets may weigh the same in GSM but have a different thickness in microns. Let me explain, for example a piece of pine and a piece of oak may be the same thickness but will be a totally different weight due to their density. The same applies during the manufacture of paper or board such as the type of coating, the amount of virgin fibres used or the bulkiness of the raw material.

This should explain why variations can occur between printed jobs using different boards that might weigh the same but that have different thicknesses. A good example is in uncoated boards with cheaper grades having the same thickness but weighing less than superior grades.

I hope you have found this blog useful, as always feel free to ask me for advice if you’re unsure.

Until the next time.