PRACTICAL GUIDE · 4 OCTOBER 2026
File size and image resolution, without the guesswork
Bytes describe the amount of data in a file. Pixels describe an image’s dimensions. Neither value on its own tells you whether a submission meets its requirements.
Keep decimal and binary units separate
A megabyte (MB) is 1,000,000 bytes. A mebibyte (MiB) is 1,048,576 bytes. A portal that says “10 MB” may use either convention informally, so follow its documented rule or leave room below the limit. HandInCheck labels each unit explicitly.
Convert the actual size
A 1 MiB file contains 1,048,576 bytes, which is 1.048576 MB. The file-size calculator converts the same byte quantity between units. Selecting a local file reads its byte size; it does not upload or compress the file.
Resolution depends on the intended physical size
Effective pixels per inch (PPI) equals pixel width divided by printed width in inches. Use the same calculation for height when the required physical height is known. Changing a metadata label to “300 DPI” does not create detail that was missing from the image.
Calculate pixels per inch
An image 2,250 pixels wide placed at 190.5 mm wide is 7.5 inches wide because 1 inch equals 25.4 mm. Its effective resolution is 2,250 ÷ 7.5 = 300 PPI. Whether 300 PPI is enough depends on the destination and image type.
Read publisher rules in context
PLOS figure guidance is an example of requirements that distinguish image dimensions, resolution and file formats. Our calculator measures effective resolution; it does not certify figure ethics, line quality, legibility, color handling, TIFF/EPS contents or compliance with every publisher rule.
Review the exported result
After resizing or exporting an image, reopen it and check its dimensions, labels and file size. A smaller file may have lost useful detail. HandInCheck’s image reader supports PNG, JPEG and WebP up to 20 MB and 40 megapixels; unsupported files need inspection in a suitable image application.