300 DPI, explained in plain English
DPI is the number print people reach for when a photo comes back blurry. It sounds technical, but it's one division problem — and once you see it, you'll know in seconds whether any file is big enough to print.
The only formula you need
DPI = pixels ÷ inches. A photo that is 1500 pixels wide, printed 5 inches wide, prints at 1500 ÷ 5 = 300 DPI — crisp. Print the same photo 10 inches wide and you get 150 DPI — noticeably soft. The file didn't change; spreading the same pixels over more paper did.
Why 300? At normal reading distance, the eye stops distinguishing detail somewhere around 300 dots per inch. Below 200, most people can see softness; below 150, text and faces look genuinely blurry. Posters viewed from across a room can get away with 150 — a program held in someone's hands cannot.
How many pixels does my print need?
| Print size | Pixels needed at 300 DPI |
|---|---|
| 4 × 6 in | 1200 × 1800 px |
| 5 × 7 in | 1500 × 2100 px |
| 8 × 10 in | 2400 × 3000 px |
| 8.5 × 11 in | 2550 × 3300 px |
Right-click any image file (or long-press in your photo app) and look at its dimensions — then divide by the inches you'll print. That's your real DPI, whatever the file claims.
"But my file says 72 DPI…"
Most files carry a DPI label in their metadata, and design tools write 72 or 96 there by default — leftovers from old screen standards. The label is not the truth; the pixels are. A 3000-pixel photo labelled "72 DPI" prints beautifully at 10 inches (3000 ÷ 10 = 300). Ignore the label, do the division.
My file is too small. Now what?
- Print it smaller. The honourable fix — a 1200 × 1800 photo is a perfect 4 × 6 even if it's a soft 8 × 10.
- Find the original. Messaging apps and social media shrink photos hard. The original from the camera or the designer is usually much bigger.
- Re-export from the design app. In Canva and similar tools, download at a larger size or as PDF Print — the design itself is resolution-independent until you export it small.
- Upscale, honestly. Software can smooth a small file so it looks less blocky, and the PrintReady fixer offers it — but no tool can invent detail that was never captured. Treat it as a last resort for small shortfalls, not a rescue.
The shortcut: you never have to do this math by hand. The PrintReady checker reads your file's real pixels and your print size, and gives you the DPI verdict instantly.
Not sure about your file?
Drop it into the free PrintReady checker. In about a second you'll see your grade, every problem, and a fixed print-ready PDF.
Check my file — free