Today A4 paper is the standard letter format adopted by all countries
in the world except the United States of America and Canada.

If you can learn the size of A4 paper (210 X 197mm), you can work out all the other sizes.

This is because you can cut in half or double up the sizes to get smaller or larger sheets of paper.

If you cut A1 in half you get 2 sheets of A2
If you cut A2 in half you get 2 sheets of A3
If you cut A3 in half you get 2 sheets of A4
If you cut A4 in half you get 2 sheets of A5
If you cut A5 in half you get 2 sheets of A6

 

Can you see the pattern in the sizes?

These might help you remember them

A1 = 594 X 840
A2 = 420 X 594
A3 = 297 X 420
A4 = 210 X 297
A5 = 148 X 210
A6 = 105 X 148

Above the coloured numbers are the same size

and below the coloured numbers are
double or half of the amount

A1 = 594 X 840
A2 = 420 X 594
A3 = 297 X 420
A4 = 210 X 297
A5 = 148 X 210
A6 = 105 X 148

There are other patterns if you look closely enough.

 

 

A4 paper is normally sold in reams. A ream is 500 sheets.

Paper is measured by its size and weight.
The weight is expressed in grams per square meter (gsm or g/m²), paper density is also known as grammage.
This is the measure used in most parts of the world.

A typical photocopy paper will be 80gsm.

Thick paper and thin card will go up to between 160 - 260gsm. However, as card becomes thicker it is no longer measured by grams per square meter, but by microns. A micron is 1 thousandth of a millimeter. A 1.2 millimeter thick board will be 1200 microns thick.