The thickness of kraft paper is usually measured in grams per square meter (g/m²) or thousandths of a millimeter (μm, also known as microns). Different thicknesses of kraft paper are suitable for different applications, the following are some common thickness ranges of kraft paper:

1. 40g/m² - 70g/m²: This is a thinner kraft paper, usually used for packaging, filling, wrapping small items, handicrafts, candy packaging, etc.

2. 80g/m² - 120g/m²: These kraft papers are slightly thicker and are suitable for general packaging, book covers, cards, labels, etc.

3. 150g/m² - 300g/m²: This is thicker kraft paper, usually used to make greeting cards, folders, gift boxes, small packaging boxes and handicrafts, etc.

4. Above 300g/m²: These are very thick kraft papers, suitable for making packaging boxes, folders, covers, business cards, greeting cards, leaflets and other applications that require higher strength and durability.

It is important to note that the thickness range of kraft paper can vary by manufacturer, so you may find different thicknesses of kraft paper on the market. When choosing the thickness of kraft paper for your specific needs, you can choose the right thickness based on the application and required strength.