OMR sheets are usually white sheets of paper with bubbles or boxes to be marked by a pencil or a pen. The thickness of a paper has no role to play in the OMR process because the OMR technology uses scanned images of these paper sheets for reading.
The OMR scanning software from Addmen reads scanned images and does not take the paper thickness into consideration.
A normal paper with 60 to 80 GSM is fine for printing.
Regular A4 sized paper with 70 GSM is usually used for printing OMR sheets.
The paper can be of any size but its accuracy rate will be 100%.
It should be noted that only white colored paper is to be used.
And, if you wish to use offset printers, then 18” X 23” sized paper is a better option.
Thick papers were a mandatory requirement in the old OMR technology because hardware scanners couldn’t scan thin papers effectively. Also, thin papers were vulnerable to distortions and bends which made scanning and printing less accurate.
Thick papers can be used in examinations to withstand damages due to handling, transportation and logistics. Hence, thicker papers with 90 to 105 GSM are used for OMR printing in such circumstances.