Image Dimensions Calculator (DPI, Pixels, Print Size)
Convert between pixels, inches, cm, and DPI. Print and screen contexts.
What this tool does
Converts between two ways of describing image size: pixel dimensions (what your screen shows) and physical dimensions plus DPI (what a printer expects). 72 DPI is the screen baseline; 150 DPI is acceptable for casual prints; 300 DPI is the print industry default; 600+ is fine-art quality. The tool also estimates raw uncompressed file size (4 bytes per pixel for RGBA) and a typical compressed JPEG size (a fraction of raw, varies by content). Calculation is local and arithmetic.
How to use it
Pick a mode. Physical to pixels: enter the print size and DPI; get the pixel dimensions you need. Pixels to physical: enter pixel dimensions and DPI; see how big it prints at that resolution. Pick units. Press Calculate. Example: an 8 x 10 inch print at 300 DPI needs a 2400 x 3000 pixel image (about 27 megapixels of data).
Common use cases
- Sizing a screenshot for a PDF that will be printed at 300 DPI.
- Checking whether a stock photo at 1200x800 is high enough resolution for a 4x6 print.
- Calculating the megapixel requirement for a billboard or large-format print.
- Converting between US (inches and DPI) and metric (cm or mm) print specifications.
- Estimating storage needs for a batch of high-resolution scans.
Common pitfalls
- DPI is metadata, not magic. Changing the DPI tag of a JPEG does not add resolution; it just changes how the file's pixels map to a print size. To increase actual detail, you need a higher-resolution capture (or AI upscaling, which fabricates).
- 72 vs 96 DPI for screens. The historical web baseline is 72 DPI; modern displays vary widely (a typical laptop is around 120 DPI; a Retina display effective resolution doubles that). For print, use 150 to 300; for screen, the DPI value matters less because browsers scale.
- Print bleed. Print jobs typically need an extra 1/8 inch on each side for the trim. Add that before calculating pixel dimensions or your printer may crop content.
Frequently asked questions
- What is the practical difference between 72, 150, 300, and 600 DPI?
- 72 DPI is the historical screen baseline. 150 is acceptable for casual prints (a photo book, a printed handout) where viewing distance is arm length. 300 is the print industry default for magazines, brochures, and most professional photo prints. 600+ is fine-art quality, suitable for poster prints viewed up close or fine line work.
- Will increasing the DPI tag of a saved JPEG make it print better?
- No. DPI is metadata describing how the file existing pixels map to a physical size. Changing the tag without changing the pixels just makes the image print smaller (more pixels per inch). To increase actual detail, capture or render at higher pixel resolution, or use AI upscaling, which fabricates plausible content based on patterns rather than recovering real detail.
- Why is my screen 72 DPI but my laptop is 220 DPI?
- 72 DPI was the original Macintosh standard and is still the default DPI tag for screen-targeted images. Modern displays vary widely: a typical desktop monitor is around 100-110 DPI; a typical laptop is 120-150; a Retina or HiDPI display is 200-300. Browsers and operating systems scale based on this, so the pixel count matters more than the DPI tag for screen images.
- How accurate is the file-size estimate?
- Raw uncompressed RGBA is exact: 4 bytes per pixel times the pixel count. The JPEG estimate is a rough heuristic (about 1/12 of raw at moderate quality). Actual JPEG size depends heavily on content: a flat-color image compresses to 1/100 of raw; a busy photo to 1/8. PNG is similar but generally larger than JPEG for photos and smaller for flat-color graphics.
- What about print bleed? Should I add to my dimensions?
- Yes, for any print job that bleeds (where ink goes to the edge). Standard bleed is 1/8 inch (3mm) per side. So a 4x6 print with bleed needs at least 4.25x6.25 inches of image. Add this margin before calculating pixel dimensions to avoid the printer cropping your content.
- How does this relate to retina or HiDPI image assets?
- For web, ship a 2x or 3x version of each asset (a 100x100 button needs a 200x200 or 300x300 source). This tool does not directly help with that; it focuses on pixel-to-physical conversion. For retina, the rule is "more pixels for the same physical size on screen," meaning treat display size as the input and pixel count as 2x or 3x of that.
Cite this tool
For academic, journalistic, or technical references. Pick a format:
Citations use 2026 as the publication year. Access date is left as a fillable placeholder where the citation style expects one.