How to use the print DPI and pixel size converter
- Pick a common size or enter width and height, then set the unit (mm, cm, inch) and DPI. The required pixels are calculated right away.
- Add an image to see the effective DPI and a sharpness verdict for printing your image at that size. If the ratio differs, choose how to fit it and the background color.
- Check the preview and save as PNG or JPG. The saved file includes the DPI information.
How pixels, DPI and print size relate
DPI means how many dots fit in one inch (25.4 mm). The same photo printed larger has fewer dots per inch, so its DPI drops, and printed smaller its DPI rises. So the pixels needed for printing are the print size in inches multiplied by the DPI you want. This free tool does that calculation and rebuilds the image at the pixel size that matches what you enter.
Many people know 72 DPI as for the web and 300 DPI as for print, but on screens the DPI number is hardly used and only the actual pixel count matters. The DPI stored in a file is just a hint about the size to print at, and it does not change quality. So changing only the DPI number from 72 to 300 means nothing; what matters is whether the pixels needed for the print size really exist.
This tool compares your image pixels with the print size, calculates the effective DPI and tells you whether it will print sharply. You can enlarge an image that lacks pixels and save it, but no new detail appears, and the tool says so. When saving, it writes the DPI into PNG pHYs and JPG JFIF density information so print software reads the size correctly.
Ideas and limits
It is useful before printing photos or framing them, to check whether the original is enough for that size. Add a photo and choose 4×6 or 8×10 inches, and the effective DPI and verdict appear, so you know how far it can be enlarged before sending it to a print shop.
Photos with set specifications, such as ID or passport photos, may have size and condition rules set by the organization. The sizes in this tool are general values, so check the guidance of the place you submit to first. It is handy for saving at the correct pixel count.
Business cards, postcards and flyers often have sizes and resolutions required by the print shop. If you need a bleed, add about 3 mm on every side to the size. For a 90×50 mm business card, enter 96×56 mm with 3 mm added on each side.
Large prints viewed from far away, such as posters and banners, can use lower DPI. At A2, 300 DPI makes the pixel count huge and the file heavy, so around 150 DPI is often more realistic.
This tool does not convert colors to print CMYK. If the print shop requires CMYK files you need a separate editing program, while ordinary photo printing usually works with RGB. Colors may also look different on a monitor and on paper.
Entering a very large size may make the browser unable to create the image. Devices such as iPhones can create only small images at a time and may fail to save. In that case lower the DPI or use a desktop browser.
Tips for preparing print images
- First check the pixel count and effective DPI verdict of the original photo.
- Aim for 250 DPI or more for prints viewed up close and around 150 DPI for large prints viewed from far away.
- If the ratio differs, check the preview and choose between cropping and margins.
- For prints that need a bleed, add it to the size you enter.
- Follow the specifications of the place you submit to or the print shop first.
FAQ
How are the pixels calculated?
The print size in mm is divided by 25.4 to get inches, then multiplied by the DPI. For example, to print A4 (210×297 mm) at 300 DPI you need 210÷25.4×300 ≈ 2,480 px and 297÷25.4×300 ≈ 3,508 px, that is 2,480×3,508 px.
Does changing a 72 DPI image to 300 DPI improve quality?
No. DPI is only print-size information stored in the file, and quality depends on the actual number of pixels. Enlarging a photo that lacks pixels does not create detail. So this tool also tells you the effective DPI you would get printing your image at that size.
What DPI prints sharply?
Photos, business cards and booklets that are viewed up close are usually printed at around 300 DPI. Posters and banners that are seen from a distance are often fine at 150 DPI or less. This tool says sharp at 250 DPI or more, may look rough up close at 150 to 249, and too low below 150.
What happens to photos with a different ratio?
Fill and crop cuts away the extra part around the center, while margin fit shows the whole photo and fills the rest with your chosen color. Stretch can distort the photo horizontally or vertically. Check the preview below and choose.
Is the DPI really stored in the saved file?
Yes. PNG gets pHYs information and JPG gets JFIF density information. You can see it in the image properties of a paint or photo editing program. Some programs ignore this value and use only the pixel count.
Notes & limitations
This tool matches size and DPI information and has no color conversion or quality improvement. Images are processed only in the browser and are not sent to a server. Check the specifications set by the place you submit to or the print shop.