Image resolution for printing comes down to one multiplication: print size in inches × pixels per inch (PPI). At 300 PPI, a 4x6 inch print needs 1200 × 1800 pixels and an 8x10 inch print needs 2400 × 3000 pixels. 300 PPI is the working figure used throughout this guide; your printer or print shop may ask for a different value, so check their specification first.
What do pixels, PPI and DPI mean?
A digital photo is a grid of pixels. It has a width and a height in pixels, such as 4000 × 3000, and nothing else fixes how large it will look on paper. The physical size appears only when you decide how many pixels go into each inch.
- Pixel: one square dot of colour in the image.
- PPI (pixels per inch): how many image pixels are spread across one inch of the printed or displayed picture.
- DPI (dots per inch): how many dots a printer places in one inch. People often say DPI when they mean PPI, which is why DPI vs PPI causes so much confusion.
For choosing a file, the number that matters is PPI, because it links the pixels you have to the inches you want. When someone asks for a "300 DPI image", they almost always mean 300 pixels for every printed inch.
How do you calculate the pixels needed for a print?
Multiply each side of the print, in inches, by the PPI you are aiming for.
Pixels = inches × PPI
To go the other way and find print size from pixels, divide instead.
Inches = pixels ÷ PPI
Worked example: you want an 8x10 inch print at 300 PPI.
- Width: 8 inches × 300 = 2400 pixels.
- Height: 10 inches × 300 = 3000 pixels.
- Your photo needs at least 2400 × 3000 pixels, which is 7.2 megapixels (2400 × 3000 = 7,200,000).
Pixel chart for common print sizes
The values below come straight from inches × PPI. The 150 PPI column is shown only so you can see how the numbers change; it is not a recommendation. A4 and A3 are converted from millimetres (210 × 297 mm and 297 × 420 mm) and rounded to the nearest pixel.
| Print size | Pixels at 150 PPI | Pixels at 300 PPI | Megapixels at 300 PPI |
|---|---|---|---|
| 4x6 in | 600 × 900 | 1200 × 1800 | 2.16 |
| 5x7 in | 750 × 1050 | 1500 × 2100 | 3.15 |
| 8x10 in | 1200 × 1500 | 2400 × 3000 | 7.2 |
| 11x14 in | 1650 × 2100 | 3300 × 4200 | 13.86 |
| A4 (210 × 297 mm) | 1240 × 1754 | 2480 × 3508 | 8.7 |
| A3 (297 × 420 mm) | 1754 × 2480 | 3508 × 4961 | 17.4 |
Halving the PPI halves the pixels on each side, so the total pixel count drops to a quarter.
How large can your photo print?
If you already have a photo, divide its pixel size by the PPI to get the print size.
| Photo size | At 300 PPI | At 150 PPI |
|---|---|---|
| 1920 × 1080 px | 6.4 × 3.6 in | 12.8 × 7.2 in |
| 4000 × 3000 px | 13.33 × 10 in | 26.67 × 20 in |
| 6000 × 4000 px | 20 × 13.33 in | 40 × 26.67 in |
For example, 4000 ÷ 300 = 13.33 inches and 3000 ÷ 300 = 10 inches. A 1920 × 1080 screen-sized image works out to only 6.4 × 3.6 inches at 300 PPI, which is why a picture that looks sharp on a monitor can be too small for a large print.
Printing the same photo bigger than its pixels support means spreading the same pixels over more inches, so the PPI falls. How that looks on paper depends on the printer, the paper and how closely the print is viewed, so ask your print shop what minimum they accept.
Does the PPI number saved in a file matter?
Not for the pixel count. An image file can carry a PPI value in its metadata, but that value is only a label for the intended print scale. Changing it does not add or remove a single pixel, so a file does not become "higher resolution" by editing that number. What counts is the width and height in pixels.
Common mistakes when preparing an image for print
- Measuring the file in kilobytes. File size depends on compression and format, so it is a poor guide to print quality. Check the pixel dimensions.
- Ignoring the shape. A 4x6 print is a 2:3 shape and an 8x10 print is a 4:5 shape. A photo with a different shape has to be cropped or printed with borders, which changes the pixels you keep.
- Cropping after you checked. Every crop removes pixels. Check the size of the cropped version, not the original.
- Mixing units. Inches and millimetres are easy to swap. One inch is 25.4 millimetres.
- Using the screen as the test. How sharp a photo looks on a screen does not tell you its pixel count, so check the width and height in pixels instead.
Checklist before you order a print
- Ask the print shop or printer what PPI or minimum pixel size they want.
- Note the exact print size in inches (or convert from millimetres).
- Multiply each side by the PPI to get the pixels needed.
- Compare with your photo's pixel width and height, after any cropping.
- Check that the shape of the photo matches the shape of the print.
- If the photo is too small, choose a smaller print size rather than guessing.
Frequently asked questions
How many pixels do I need for a 4x6 print? At 300 PPI you need 1200 × 1800 pixels (4 × 300 and 6 × 300). Confirm the PPI your printer or shop asks for.
What is the difference between DPI and PPI? PPI counts image pixels per inch. DPI counts the dots a printer lays down per inch. In everyday use, people often say DPI when they mean PPI.
Can I make a low-resolution photo print-ready by changing its DPI setting? No. Changing the stored value does not change the number of pixels in the file.
How do I find the print size of my photo from its pixels? Divide the pixel width and height by the PPI. A 4000 × 3000 photo at 300 PPI is 13.33 × 10 inches.
How many megapixels is an 8x10 print at 300 PPI? 2400 × 3000 = 7,200,000 pixels, or 7.2 megapixels.
Check your own numbers
The maths above is simple, but it is easy to slip when you are converting between inches, millimetres and pixels. If you would rather not do it by hand, the free DPI Calculator on BytePriva runs in your browser and does the same pixel, size and PPI conversions for you. Whichever way you calculate, confirm the final requirement with your printer.
Disclaimer
This guide is general information. Required resolution varies by printer, paper, viewing distance and shop rules, so follow the specification of the service that will print your file. Written by the BytePriva Team. Last reviewed: 23 October 2026.