Created by: PrintForFun. Reviewed and updated by the KT Colour team, October 2026.
The short answer: find the photo's size in pixels, divide both numbers by 300, and the result is the largest print in inches that will look sharp up close. A 3000 x 4000 pixel phone photo prints sharp at 10 x 13 inches, so anything up to 8R or A4 is safe. A 1200 x 1600 photo from WhatsApp is good for 4R and no bigger. Or skip the maths and drop the file into our Print Size Calculator, which does this for you without uploading anything.
Most disappointing prints come from photos that looked perfect on screen. A screen only needs a couple of million pixels to look sharp; a print needs far more per inch, because you hold it close and the paper shows every pixel. The photo did not get worse. It was always too small for the size you ordered.
The 300 rule
Print labs talk about pixels per inch, often written dpi. At 300 pixels per inch, a print looks completely smooth from any distance. At 200 it still looks sharp at arm's length, which is why large posters and canvas are fine at 200 or even 150. Below about 150, you start to see softness and, eventually, blocks.
So the question "is 1800 x 1200 good enough?" has no answer on its own. For a 4R print (4 x 6 inches) it is exactly 300 per inch, which is perfect. For an 8R (8 x 10 inches) it is 150 per inch, which is noticeably soft. The size you want to print is half of the question.
How to see a photo's pixel size
- iPhone: open the photo, tap the "i" button or swipe up. The size is shown under the camera details, for example 4032 x 3024.
- Android: open the photo, tap the three-dot menu, then Details or Info.
- Windows: right-click the file, choose Properties, then the Details tab.
- Mac: select the file and press Cmd + I, or open it in Preview and choose Tools > Show Inspector.
Then divide. 4032 ÷ 300 = 13.4 and 3024 ÷ 300 = 10.1, so that photo prints sharp up to about 10 x 13 inches, and acceptably at 200 per inch up to 15 x 20 inches.
Where the small copies come from
| Source | Typical size | Largest sharp print |
|---|---|---|
| Phone camera, original | 3000 x 4000 or more | A3, 12R, posters at 200 ppi |
| WhatsApp, sent as photo | about 1200 x 1600 | 4R. Ask for it as a document instead. |
| Facebook download | 1080 to 2048 long side | 4R to 5R |
| Instagram download | 1080 x 1350 | 4R |
| Screenshot | your screen size, often 1170 x 2532 | 4R at best, and the edges are usually wrong |
| Old digital camera (5 MP) | 2592 x 1944 | 6R or 8R |
The fix is nearly always the same: go back to the device that took the photo and send the original. If a friend took it, ask them to share it as a file or document rather than a photo, which skips the compression.
Pixels needed for each size we print
| Size | Inches | Pixels for 300 ppi | Fine at 200 ppi |
|---|---|---|---|
| 2R (wallet) | 2.5 x 3.5 | 750 x 1050 | 500 x 700 |
| 3R | 3.5 x 5 | 1050 x 1500 | 700 x 1000 |
| 4R | 4 x 6 | 1200 x 1800 | 800 x 1200 |
| 5R | 5 x 7 | 1500 x 2100 | 1000 x 1400 |
| 6R | 6 x 8 | 1800 x 2400 | 1200 x 1600 |
| 8R | 8 x 10 | 2400 x 3000 | 1600 x 2000 |
| S8R | 8 x 12 | 2400 x 3600 | 1600 x 2400 |
| A4 | 8.3 x 11.7 | 2480 x 3510 | 1660 x 2340 |
| A3 | 11.7 x 16.5 | 3510 x 4960 | 2340 x 3300 |
| 12R | 12 x 16 | 3600 x 4800 | 2400 x 3200 |
The full list, including square, IKEA and poster sizes, is on our photo print sizes guide.
Two exceptions
Distance helps. A print on a wall is viewed from a metre or more away, where 150 pixels per inch looks as sharp as 300 in the hand. That is why a 12 megapixel phone photo makes a perfectly good A1 poster or 24 x 36 inch canvas.
Small prints forgive. If all you want is a 4R or a retro print, a WhatsApp copy or even a screenshot will usually do. Save the hunt for the original for anything 8R and above.
Free tool
Drop in a photo, get a verdict for every size
The Print Size Calculator reads the pixel size in your browser and shows a preview of the largest sharp print. Nothing is uploaded.