Printing photos
300 DPI for print: what it means, how to check
Quick answer: DPI is not a quality stamp on a file. It says how many pixels are spread over one inch of paper when the picture is printed. A photo is ready for a sharp print when it has enough pixels for the size you want (about 300 per inch), and changing the DPI number in the file does not add any. Open the print size checker to see how large your photo prints sharply and, if a form or print shop asks for it, save a copy with the DPI value written in. It runs in your browser; nothing is uploaded.
Files are processed locally.
On this page
DPI, PPI and pixels: three different things
A digital photo is a grid of pixels, for example 3000 × 2000. Nothing in that grid is measured in inches. The inch only appears when you print: the print size is the pixel count divided by the resolution you print at. 3000 pixels at 300 per inch make 10 inches (25.4 cm); the same 3000 pixels at 150 per inch make 20 inches.
- Pixels
- The real size of the picture, such as 3000 × 2000. This decides detail.
- PPI / DPI value in the file
- A note that says “print me at this many pixels per inch”. Programs may use it as a suggestion for the print size.
- Printer DPI
- How many ink dots a printer can place per inch. It is a printer property, not a property of your photo.
- 72 DPI
- An old screen convention. Web pages and apps ignore it; it does not make a file smaller or worse.
Background: Dots per inch on Wikipedia, checked 5 October 2026. Refentra is not affiliated with Wikipedia.
How many pixels do you need?
Multiply the print size in inches by the resolution. About 300 pixels per inch looks sharp when you hold the print in your hands; around 150 is fine for most everyday prints; large posters seen from a distance can go lower. These are rules of thumb, not laws.
- 4 × 6 in
- 1200 × 1800 px at 300 DPI · 600 × 900 px at 150 DPI
- 10 × 15 cm
- 1181 × 1772 px at 300 DPI · 591 × 886 px at 150 DPI
- 13 × 18 cm
- 1535 × 2126 px at 300 DPI · 768 × 1063 px at 150 DPI
- 8 × 10 in
- 2400 × 3000 px at 300 DPI · 1200 × 1500 px at 150 DPI
- A5
- 1748 × 2480 px at 300 DPI · 874 × 1240 px at 150 DPI
- A4
- 2480 × 3508 px at 300 DPI · 1240 × 1754 px at 150 DPI
- A3
- 3508 × 4961 px at 300 DPI · 1754 × 2480 px at 150 DPI
Calculated: centimetres ÷ 2.54 × DPI, rounded to whole pixels. Print shops may crop photos slightly, so leave a little extra.
Check your photo and set the DPI value
- Use the original file. Photos sent through messengers or saved from social media are often much smaller than what your camera took.
- Open the print size checker and choose the JPG or PNG. It shows the pixel size, any DPI already stored in the file and a table of common print sizes with a rating for each.
- Read the table. “Sharp” means about 300 pixels per inch or more for that sheet, “Fine for most uses” 150–299, “May look soft” below 150. Choose the sheet size accordingly.
- Only if someone asks for a DPI value: pick 300 (or another value) and select Save. The tool writes the number into the file, re-reads it and confirms that the picture data is identical.
- Send that copy to the print shop or upload it. Keep the original.
When a form asks for “300 DPI”
- Many upload forms check the pixel size or the file size, not the DPI value. Read the exact wording: “minimum 600 × 600 px” is about pixels, “at least 300 DPI” can be checked in the file’s density field.
- If the form checks the DPI value, saving a copy with the value written in usually satisfies it. If it still rejects the file, the pixel size is probably too small.
- Do not scale a small picture up just to reach a number. The file gets bigger, not sharper. See image too large or too small for upload.
What the tool does and does not do
- It works with one still JPG or PNG up to 25 MiB. WebP, HEIC and animated files are not supported.
- It changes only the stored density: the picture data is copied byte for byte and compared after writing. A JPEG can carry the value in two places (JFIF and EXIF); both are updated when both exist.
- It does not enlarge, sharpen or convert the image. If you need other pixel dimensions, use the resize tool.
Sources and method
The pixel table is calculated from the formula above. The explanation of the terms follows the linked reference, checked on 5 October 2026. Tool steps and limits were checked against the current Refentra print size tool, and written files were read back with ImageMagick. This guide was drafted and edited with AI assistance.