How to use the DPI & Print Size Calculator
- Pick a direction. Image → print size answers “how big can I print this?”; Print size → pixels answers “how many pixels do I need for an 18 × 24?”.
- Give it the numbers. Drop a JPG, PNG, WebP or GIF on the box to read its exact pixel size — the file is read by your browser and never uploaded — or type the width and height. In the second tab, type the print size or tap a chip such as 8×10″ or A3.
- Set the print resolution. Tap 150, 200, 240, 300 or 600, or type any value. The panel underneath rates that resolution and tells you the distance from which a print at that DPI looks sharp to normal eyesight.
- Scan the table. With an image loaded, the table shows the effective DPI at every common print size, from 4 × 6 to 24 × 36 in — switch to A sizes for A5 to A1 — plus how much gets cropped when the shape differs. In the second tab it checks whether a 12, 24 or 48 MP camera can cover the print.
- Copy the numbers. Copy summary, under the table, puts the print size, the pixel counts and the DPI at every size on your clipboard for an email to your print shop.
What DPI really decides
For printing, DPI means how many of your image’s pixels are spread across each inch of paper. Strictly that’s PPI, pixels per inch — the printer’s own ink-dot density is a separate, much higher number — but print labs, clients and most software menus use the two terms interchangeably. The arithmetic is one division: pixels ÷ DPI = inches. A 3024 × 4032 phone photo at 300 DPI prints at 10.08 × 13.44 in.
The DPI written inside the file is only a label. A JPEG tagged 72 DPI and the same JPEG tagged 300 DPI contain identical pixels; the tag just changes the default size an app proposes when you hit Print. At 72 DPI that phone photo would offer itself as 42 × 56 in, at 300 DPI as 10 × 13. When a client insists on “a 300 DPI file”, what they actually need is enough pixels for their print size.
So why 300? Normal 20/20 vision resolves details about one arcminute apart. At a reading distance of 12 in (30 cm) that works out to roughly 286 dots per inch, and 300 is the round number above it. The required resolution falls as the viewer steps back — the rule of thumb is 3438 ÷ viewing distance in inches:
- 12 in (30 cm), a print in your hands: 286 DPI
- 24 in (61 cm), a print on a desk or a small wall piece: 143 DPI
- 36 in (91 cm), a poster across a hallway: 96 DPI
- 72 in (1.8 m), a large piece across a room: 48 DPI
That is why a 24 × 36 in poster at 150 DPI looks fine on the wall and why billboards get away with tiny resolutions. It’s also why the quality bands in the calculator start at 300 for gallery work, accept 240 for photo-lab prints, and call 150 “poster” quality.
Pixels needed for common print sizes
Fill the whole sheet at each resolution with these pixel dimensions. If you’re setting up a digital canvas, start from the 300 DPI column.
| Print size | 300 DPI | 240 DPI | 150 DPI | Megapixels at 300 |
|---|---|---|---|---|
| 4 × 6 in | 1,200 × 1,800 | 960 × 1,440 | 600 × 900 | 2.2 |
| 5 × 7 in | 1,500 × 2,100 | 1,200 × 1,680 | 750 × 1,050 | 3.1 |
| 8 × 10 in | 2,400 × 3,000 | 1,920 × 2,400 | 1,200 × 1,500 | 7.2 |
| 11 × 14 in | 3,300 × 4,200 | 2,640 × 3,360 | 1,650 × 2,100 | 13.9 |
| 16 × 20 in | 4,800 × 6,000 | 3,840 × 4,800 | 2,400 × 3,000 | 28.8 |
| 18 × 24 in | 5,400 × 7,200 | 4,320 × 5,760 | 2,700 × 3,600 | 38.9 |
| 24 × 36 in | 7,200 × 10,800 | 5,760 × 8,640 | 3,600 × 5,400 | 77.8 |
| A4 (210 × 297 mm) | 2,480 × 3,508 | 1,984 × 2,806 | 1,240 × 1,754 | 8.7 |
| A3 (297 × 420 mm) | 3,508 × 4,961 | 2,806 × 3,969 | 1,754 × 2,480 | 17.4 |
| A2 (420 × 594 mm) | 4,961 × 7,016 | 3,969 × 5,613 | 2,480 × 3,508 | 34.8 |
A 12-megapixel phone photo (3024 × 4032) clears 300 DPI up to 8 × 10 in and A4, reaches photo-lab quality at 11 × 14 in (275 DPI), and drops to 189 DPI at 16 × 20 in. A 24 MP camera holds 250 DPI at 16 × 20 in.
Tips from practice
Start digital paintings at print size. Upscaling later adds pixels but no detail. If a piece might become an 11 × 14 in print, open the canvas at 3300 × 4200 px from the start; the Digital Canvas Size for Print tool has presets for Procreate and Photoshop limits.
Don’t fake 300 DPI. Changing the number in Image Size with resampling switched off only edits the label; with resampling on, software invents in-between pixels. Neither makes a soft file sharper. Send the real pixel count and let the lab decide.
Check the DPI after cropping. A 4 × 6 print from a 3:4 phone photo loses 11.1% of the picture, and the effective DPI is calculated on what’s left. The Cropped column shows it before you discover a missing hand or signature on the print.
Give line art and lettering extra resolution. Soft photos hide low DPI; crisp ink lines and small type show jagged edges first. Scan inked drawings at 600 DPI and lettering-heavy designs at no less than 300, even for posters.
Use the printer’s number if they give one. Some inkjet workflows prefer 360 or 720 DPI rather than 300 or 600. If your print shop names a resolution, resize to it once at the end, from your largest master file.