Tool
Paper Size & Weight Converter
Convert between A-series, US and imperial paper sizes, and between gsm and lb paper weights.
Paper weight is measured in gsm (grams per square metre) in most of the world and in lb in the US. Because lb depends on the paper type's basis size, conversion is not a single number: 140 lb drawing or watercolour paper is about 300 gsm.
How to convert paper size and weight
- Find the nearest standard size. Enter a width and height in mm, cm or inches to see which standard paper size is closest.
- Convert paper weight. Enter gsm or lb and choose the paper type, because the lb number depends on the basis sheet size.
- Browse the size table. The standard sizes table lists A-series, US and common art sizes in all units.
Choosing a paper size for drawing
The A-series is the easiest system to plan with: every size has the same proportion, so a composition designed on A4 scales perfectly to A3 or A2. If you sell or exhibit work, standard sizes also make framing dramatically cheaper because off-the-shelf frames and mounts exist for them.
Imperial sizes such as 9 × 12 in and 11 × 14 in remain common for pads and blocks. The converter shows every size in millimetres, centimetres and inches, and the nearest-size finder tells you how far your own sheet is from a standard one.
Paper weight in gsm and lb
For coloured pencil, weight matters because layering builds up pigment and repeated erasing wears the surface. 300 gsm (about 140 lb) is a common sweet spot for heavy layering: it stays flat and resists damage.
Frequently asked questions
How do A-series paper sizes work?+
Each A size is half the area of the one above, made by cutting the longer side in half. Every size has the same 1:1.414 proportion, so an A4 drawing enlarges cleanly to A3 or reduces to A5 with no cropping.
What is gsm?+
GSM means grams per square metre - the weight of one square metre of the paper. Heavier gsm generally means thicker, sturdier paper that copes better with layering, erasing and wet media.
Why is lb not a direct conversion from gsm?+
US pound weight is the weight of a 500-sheet ream at a particular basis sheet size, and that basis size differs between paper types. The conversion therefore depends on which type of paper you are converting.
What gsm is 140 lb watercolour or drawing paper?+
Around 300 gsm. 90 lb is roughly 190 gsm, and 300 lb is roughly 640 gsm on the drawing and watercolour basis.
What is 140 lb paper in gsm?+
140 lb watercolour or drawing paper is about 300 gsm. 90 lb is about 190 gsm and 300 lb is about 640 gsm.
What is the difference between A4 and US Letter?+
A4 is 210 x 297 mm. US Letter is 8.5 x 11 in (about 216 x 279 mm), slightly wider and shorter.
What gsm paper is best for coloured pencils?+
Heavier is generally better for layering. 150 to 200 gsm handles light work, and 250 gsm or more copes with many layers and burnishing.
How many cm is A3?+
A3 is 29.7 x 42 cm (297 x 420 mm), exactly twice the area of A4.