OMR in one paragraph
OMR stands for optical mark recognition. A candidate fills bubbles on a printed answer sheet; the sheet is scanned or photographed; the software finds the sheet in the image, measures how dark each bubble is, and records the filled ones as answers. It then compares them with the answer key, adds up the marks and produces a results list.
How OMR software reads a sheet
- Locate the page. Printed reference marks, usually black squares in the corners, tell the software where the sheet is in the image.
- Correct the angle. The position of those marks is used to undo tilt and perspective, so every bubble is measured in the right place.
- Measure the bubbles. Each option is checked for ink. One clear mark is an answer; two marks or none need a decision.
- Read identifiers. Bubbled roll numbers and printed sheet numbers link the sheet to a candidate.
- Mark and export. Answers are scored against the key, including any negative marking, and saved as a spreadsheet or report.
OMR software, OMR machines and phone apps
| Question | OMR software | OMR scanner machine | Phone app |
|---|---|---|---|
| What it is | A program on a PC that reads scanned images or photos | A dedicated machine that reads sheets as they feed through it | A phone app that reads photographed sheets |
| Paper | Plain paper, printed on an ordinary printer | Usually precision-printed forms bought for the machine | Plain paper, printed on an ordinary printer |
| Sheet design | Designed in the software for each exam | Fixed by the form supplier | Designed in the app, or a fixed template |
| Hardware | A PC, a printer, and a scanner or camera | The OMR machine and its PC | The phone you already have |
| Best for | Schools and exam offices marking stacks of sheets | Very large, centralised exams | Teachers marking one class at a time |
OMR Software for Windows is the first kind; the OMR Sheet Android app is the third. Both read the same sheets.
Checklist for accurate results
- Print on the paper size the sheet was designed for, at 100% scale.
- Print and grade one test sheet before printing the whole batch.
- Ask candidates to fill bubbles completely with a dark pen or pencil.
- Scan in greyscale at about 300 DPI, with auto-crop and de-skew switched off.
- Keep all four corner markers inside every scan or photo.
- Review every sheet the software flags before saving results.
Common questions
What does OMR stand for?
- Optical mark recognition: reading marks, such as filled bubbles, from paper by looking at where the ink is.
Do I need an OMR machine to use OMR software?
- No. OMR software reads images, so a document scanner, a flatbed scanner or a phone camera can supply them. A dedicated OMR machine is a different product.
What is the difference between OMR, OCR and ICR?
- OMR reads marks in fixed positions, such as bubbles. OCR reads printed text, and ICR reads handwriting. Multiple-choice answer sheets only need OMR.
How accurate is OMR software?
- It depends on the sheet, the printing and the scan. Good software also tells you when it is unsure, for example when two bubbles are filled or a corner marker cannot be found, so a person can check that sheet.