72, 150, 300, 600 DPI — What's the Difference?
Published June 2026 · 8 min read · DPI & Resolution
DPI is one of the most misunderstood concepts in digital imaging. Most people pick a number without knowing why, apply it to every image without thinking, and end up confused when a print shop asks for "300 DPI" for a file that's already stored as 72 DPI. This guide explains what DPI actually means, what each value is used for, and why changing DPI doesn't do what most people think it does.
What DPI actually means
DPI stands for dots per inch. It describes how many ink dots a printer places per linear inch of paper. A 300 DPI inkjet printer places 300 tiny dots in every inch — that's 90,000 dots in a single square inch. More dots per inch means finer detail, smoother gradients, and sharper text.
For digital image files, DPI is metadata — a stored value that tells software how large to print or display the image. It lives in the file header (JFIF or EXIF for JPEGs, the pHYs chunk for PNGs). It does not affect the pixel data in any way.
This is the crucial distinction that trips most people up:
DPI is a label, not a measure of quality. A 3000 × 2000 pixel image labelled 72 DPI and the same image labelled 300 DPI have identical pixel data. They look identical on screen. What changes is how large the image prints.
How DPI affects print size (the math)
If you have a 3000 × 2000 pixel image and want to know how large it will print, divide the pixel count by the DPI:
- At 72 DPI: 3000 ÷ 72 = 41.7 inches wide (105 cm)
- At 150 DPI: 3000 ÷ 150 = 20 inches wide (50 cm)
- At 300 DPI: 3000 ÷ 300 = 10 inches wide (25 cm)
- At 600 DPI: 3000 ÷ 600 = 5 inches wide (12.5 cm)
Same pixels, four very different print sizes. Changing DPI does not add pixels — it changes only the intended print size. To actually print larger at 300 DPI, you need more pixels (either from a higher-resolution camera, or from the Upscale Image tool).
72 DPI — web and screen use
72 DPI is the historical convention for screen images, dating from the 1984 Macintosh (which had a 72 PPI display). Today, it means almost nothing for digital display. Screens measure resolution in pixels per inch (PPI) — 1080p laptop screens have ~166 PPI, 4K monitors ~220 PPI, and Retina displays ~220–460 PPI. They completely ignore the DPI metadata in the image file.
When to use 72 DPI: Web images, social media, email, any image that will only ever be viewed on screen. The DPI value doesn't matter — what matters is pixel count. Use the correct pixel dimensions for the platform (e.g., 1200 × 630 px for Open Graph / social sharing, 1080 × 1080 px for Instagram).
What "72 DPI" actually does: At 72 DPI, a 3000 × 2000 px image would print at ~41 × 28 inches. If someone tries to print a web-resolution "72 DPI" image, it prints huge and blurry. This is often what people mean when they say "the image is too low quality to print" — the pixel count is too low for the print size, not the DPI label.
150 DPI — draft printing and large format
150 DPI sits between web resolution and professional print. At this density, dots are visible to someone with good eyesight looking very closely, but at normal viewing distances (arm's length or further) most people can't see individual dots.
When to use 150 DPI:
- Draft prints for proofing — speed and ink saving over 300 DPI
- Large format output (banners, posters, signs) that are viewed from 2+ metres away — lower DPI is fine because the viewer is further from the dots
- A2 or larger poster prints where you want a larger physical size from a given pixel count
A 6000 × 4000 px photo prints at 40 × 26.7 inches at 150 DPI — a large poster. At 300 DPI, the same file prints at 20 × 13.3 inches. The detail is identical; the size differs.
300 DPI — the universal standard for printing
300 DPI is the de facto standard for photo printing, document printing, and professional graphic design. At 300 DPI, ink dots are 1/300th of an inch each — too small to distinguish individually at normal viewing distance (approximately 30 cm / 12 inches). The result looks smooth and continuous to the eye.
When to use 300 DPI:
- Standard photo printing at any consumer or professional lab
- Business cards, brochures, leaflets, posters
- Documents submitted to publishers or government agencies
- Passport photos (see the Passport Photo tool — all country standards output at 300 DPI-equivalent pixel dimensions)
- Product photos for e-commerce when printing samples or lookbooks
300 DPI at common print sizes requires these pixel counts:
| Print size | Pixels needed at 300 DPI |
|---|---|
| 4 × 6 inches (10 × 15 cm) | 1200 × 1800 px |
| 5 × 7 inches (13 × 18 cm) | 1500 × 2100 px |
| 8 × 10 inches (20 × 25 cm) | 2400 × 3000 px |
| A4 (8.3 × 11.7 inches) | 2480 × 3508 px |
| A3 (11.7 × 16.5 inches) | 3508 × 4961 px |
| US Letter (8.5 × 11 inches) | 2550 × 3300 px |
| 2 × 2 in passport photo | 600 × 600 px |
To set your image to 300 DPI without losing quality, use the free Convert to 300 DPI tool — it rewrites only the header, not the pixels.
600 DPI — professional and archival use
600 DPI doubles the dot density of 300 DPI. The difference is rarely visible at normal viewing distances with photographic content — but it matters in specific professional contexts where fine detail, small text, or extreme close-up viewing is involved.
When to use 600 DPI:
- Archival scanning of printed photographs, slides, or documents — capturing maximum detail from the original
- Fine art giclée printing on canvas or rag paper, viewed at close distance
- Medical imaging — radiology reports, pathology slides, journal figure submissions often specify 600 DPI
- OCR (optical character recognition) input — character recognition accuracy improves significantly at 600 DPI vs 300 DPI
- Drum scanners — professional film and art scanners often operate at 600, 1200, or higher DPI
- Academic journal submissions — many journals specify 600 DPI minimum for line art figures
To convert a JPG or PNG to 600 DPI losslessly, use the Convert to 600 DPI tool.
Does changing DPI affect quality?
Changing the DPI value alone does not affect quality. It only changes the intended print size. If you change 72 DPI to 300 DPI in a header rewrite tool (like the ones on myPixelVault), the pixels stay identical — the file looks the same on screen, and will print at a different size at 300 DPI than it would have at 72 DPI.
Where quality can be affected:
- Resampling: If a tool changes DPI and adds or removes pixels to maintain a fixed print size, that changes quality. Software like Photoshop offers "Resample" and "No Resample" modes. "No Resample" changes only the header; "Resample" adds or removes pixels.
- Upscaling: Creating new pixels (as opposed to relabelling existing ones) introduces some interpolation quality trade-off. AI upscalers like the Upscale Image tool do this much better than classical bicubic interpolation.
Quick reference: which DPI for which use case
| Use case | DPI | Why |
|---|---|---|
| Social media images | 72 (or any) | Screen ignores DPI — pixel count is what matters |
| Web & email images | 72 (or any) | Browsers ignore DPI |
| Consumer photo printing | 300 | Standard for photo labs |
| Business cards, brochures | 300 | Standard for offset and digital print |
| Passport photos | 300 | Required by most countries' digital submission systems |
| Large format banners / signage | 100–150 | Viewed from distance; lower DPI = larger output size |
| Fine art / giclée printing | 300–600 | Close viewing; premium printers support 600+ |
| Medical imaging / journals | 600 | Specified by submission guidelines |
| Archival scanning | 600+ | Maximise captured detail from originals |
| OCR input files | 300–600 | Higher accuracy for character recognition |
How to check and change DPI
To see what DPI your image is currently stored at, use the free EXIF Viewer tool — it shows the stored resolution alongside other metadata.
To change DPI:
- DPI Converter (any value) — type any DPI value, lossless header rewrite for JPEG and PNG
- Convert to 300 DPI — preset to 300, for print submissions
- Convert to 600 DPI — preset to 600, for archival and professional workflows
All three tools rewrite only the file header — no pixels are changed, no quality is lost, and no file is uploaded to any server.
Frequently Asked Questions
What does DPI mean?
DPI stands for dots per inch. It tells a printer how many ink dots to place per inch of paper. In digital image files, it's metadata stored in the header — it describes the intended print size without affecting the pixel data.
Does changing DPI change image quality?
No. Changing the DPI label in a header rewrite does not add, remove, or modify any pixels. Quality change only occurs if a tool resamples (adds or removes pixels) while changing DPI. The tools linked above are header-only — they change no pixels.
What DPI should I use for printing?
300 DPI is the standard for consumer and professional photo printing. It produces dots too small to see at normal viewing distance. For very large format output (banners viewed from 2+ metres), 100–150 DPI is sufficient and allows a larger physical print size from the same pixel count.
What DPI do I need for web images?
Screens ignore DPI entirely — use any value, typically 72. What matters for web images is pixel count: how many pixels wide and tall the image is. DPI has no effect on how an image appears on screen.
When do I need 600 DPI?
600 DPI is used for archival scanning, fine art printing, medical and scientific imaging, and OCR input files. For standard consumer photo printing, the output looks identical at 300 DPI and 600 DPI — the difference only appears at very close viewing distances with content that has fine lines or small text.