How to Calculate PDF Scan Resolution
Estimate the effective scan resolution of a rasterized PDF page by comparing pixel width with the page’s physical width. This is useful when checking whether a scan is suitable for OCR, archiving or print reproduction.
Example
A page that is 2480 pixels wide across an A4 width of 210 mm is approximately 300 DPI.
Factors That Affect the Result
The estimate depends on accurate pixel and physical dimensions. Resampling, image compression, cropping and mixed-resolution pages can make a single DPI value less representative of the whole document.
Frequently Asked Questions
What DPI is common for document scanning?
About 300 DPI is a common target for readable text and OCR.
Does higher DPI always mean better OCR?
No. Blur, contrast, skew and compression also matter.
Does this tool inspect the PDF automatically?
No. You enter the dimensions manually.
DPI, Page Size and Scan Detail
Scan DPI describes sampling density. Higher DPI captures more pixels across the same physical page and can improve small-text detail, but it also increases image data and file size. The useful setting depends on source quality, text size, color mode and whether OCR or printing is required.
DPI, Page Size and Scan Detail
Scan DPI describes sampling density. Higher DPI captures more pixels across the same physical page and can improve small-text detail, but it also increases image data and file size. The useful setting depends on source quality, text size, color mode and whether OCR or printing is required.
Technical Details and Practical Limits
Scan DPI describes sampling resolution, but higher DPI does not guarantee better OCR or smaller files. Text size, source sharpness, compression and color mode matter; 300 DPI is common for text, while fine detail may justify higher resolution.