Print Size Resolution Calculator
Calculates the uncompressed file size in megabytes required to print an image at a given size, DPI, and color depth. Use it to verify your camera file has enough resolution before sending a print to a lab.
About this calculator
Print resolution is measured in dots per inch (DPI), and the total number of pixels required equals printWidth × DPI by printHeight × DPI. The uncompressed file size in megabytes is then determined by how many bits are used to store each pixel's color information (color depth). The full formula is: fileSizeMB = (printWidth × printHeight × DPI² × colorDepth) / 8,388,608, where 8,388,608 = 8 bits/byte × 1,048,576 bytes/MB. A standard 24-bit RGB image uses 8 bits per channel across 3 channels. At 300 DPI — the professional print standard — an 8×10 inch print needs roughly 7.2 MP of image data. Knowing the required file size helps you choose the correct camera resolution, scanning resolution, or interpolation settings before printing.
How to use
You want to print an 8×10 inch photo at 300 DPI in 24-bit RGB color (colorDepth = 24). Plug in: printWidth = 8, printHeight = 10, dpi = 300, colorDepth = 24. fileSizeMB = (8 × 10 × 300² × 24) / 8,388,608 = (8 × 10 × 90,000 × 24) / 8,388,608 = 172,800,000 / 8,388,608 ≈ 20.6 MB. Your uncompressed image file must be at least 20.6 MB to print at this quality. A JPEG will be smaller due to compression, but the underlying pixel count must still meet this requirement.
Frequently asked questions
What DPI should I use for professional photo printing?
The industry standard for professional photo prints is 300 DPI, which is the resolution at which the human eye can no longer distinguish individual dots at normal viewing distances (about 30 cm). For large-format prints viewed from a distance — such as banners or exhibition prints — 150 DPI is often acceptable and significantly reduces file size. Inkjet photo printers typically print at 1440 or 2880 DPI natively, but they interpolate the image data, so your file only needs to be 240–360 DPI. Sending a file above 400 DPI rarely improves visible print quality and simply increases processing time.
How does color depth affect photo print file size?
Color depth determines how many distinct shades each color channel can record. A standard 24-bit image has 8 bits per channel across red, green, and blue, giving 256 shades per channel and over 16 million total colors. A 48-bit image (16 bits per channel) doubles the file size but captures finer tonal gradations, which is useful when editing and printing images with smooth gradients like skies. For most print labs, 24-bit (8-bit per channel) is sufficient. Higher bit depths become important in the editing workflow but are often downsampled before final print output.
How many megapixels do I need to print a high-quality 16×20 inch photo?
At 300 DPI, a 16×20 inch print requires 4,800 × 6,000 pixels, which equals approximately 28.8 megapixels. At 240 DPI — still considered good quality — the requirement drops to 3,840 × 4,800 pixels, or about 18.4 MP. Most modern mirrorless and DSLR cameras with 20–45 MP sensors can cover a 16×20 at 300 DPI comfortably. If you are cropping the image significantly, calculate based on the cropped pixel dimensions rather than the full sensor resolution.