A photo that looks flawless on your monitor can come back from the printer soft, pixelated, and disappointing. Nothing went wrong in transit. The image was simply never carrying enough information for the size it was printed at — and screens are far too forgiving to have warned you.
Print is a fundamentally different medium from the web, and almost every optimisation instinct you have built up for websites works against you here. Where optimising for the web is about aggressively removing data, print is about retaining it.
The one idea that makes DPI make sense
A digital image has no physical size. A 3000×2000 image is not "large" or "small" — it is simply a grid of 3000 by 2000 pixels. It acquires a physical size only when you decide how densely to pack those pixels onto paper.
That density is DPI: dots per inch. And the relationship is pure arithmetic:
pixels = inches × DPI
Print those 3000 pixels across 10 inches and you get 300 DPI — sharp. Stretch the same 3000 pixels across 30 inches and you get 100 DPI — visibly soft. The file did not change. Only the density did.
This is why "save it at 300 DPI" is, on its own, meaningless advice. DPI is not a quality setting stored in the image; it is a number in the metadata that says how big to print. Changing it without changing the pixel count just changes the intended print size. If your image has 1000 pixels across and you set the metadata to 300 DPI, you have not improved anything — you have declared that it should print 3.3 inches wide.
DPI vs PPI, briefly. Strictly, PPI (pixels per inch) describes the image and DPI (dots per inch) describes the ink droplets a printer lays down; a printer may use many droplets per pixel. In everyday use the two are used interchangeably, and for the purpose of "how many pixels do I need", the formula above is what matters.
The pixel dimensions you actually need
Standard practice is 300 DPI for anything held and read at normal distance. Multiply the print size in inches by 300:
| Print size | Physical size | Pixels needed at 300 DPI |
|---|---|---|
| Business card | 3.5×2 in | 1050×600 |
| 4×6 photo | 4×6 in | 1200×1800 |
| 5×7 photo | 5×7 in | 1500×2100 |
| A5 | 148×210 mm | 1748×2480 |
| 8×10 photo | 8×10 in | 2400×3000 |
| A4 | 210×297 mm | 2480×3508 |
| US Letter | 8.5×11 in | 2550×3300 |
| A3 | 297×420 mm | 3508×4961 |
A useful sanity check: a 12-megapixel phone photo (roughly 4000×3000) prints beautifully at A4 and is comfortably enough for A3 at a slightly lower density. Modern phone cameras are not the limiting factor for ordinary print sizes — the limiting factor is almost always that the file was resized down for the web at some point along the way.
300 DPI is not a universal law. It is the standard for viewing distance of roughly 30 cm. The further away something is read, the less density it needs:
- Books, magazines, flyers, photo prints: 300 DPI.
- Posters viewed from a metre or more: 150–200 DPI is genuinely fine.
- Large-format banners and billboards: 30–100 DPI. A billboard at 300 DPI would be an unprintable, absurd file — nobody stands 30 cm from a billboard.
- Fine-art and giclée printing: some printers ask for 360 or 600 DPI.
Ask your printer rather than guessing. Over-supplying resolution is harmless; under-supplying is not fixable at the press.
Why you cannot rescue a low-resolution image
If you have a 800×600 image and need 2480×3508 for A4, upscaling seems like the obvious answer. It is not a real solution, and it is worth being precise about why.
Enlarging invents pixels that were never captured. Traditional interpolation guesses each new pixel by averaging its neighbours, which is mathematically reasonable and visually soft — you get a bigger image with no more actual detail, plus a slightly blurred, plasticky quality. AI upscalers do better by hallucinating plausible detail learned from other images, which can look impressive, but the invented texture is not the texture that was in front of the lens. For a landscape it may be undetectable; for a face, a logo, or fine text, the fabrication tends to show.
The practical rule: modest enlargement is fine, large enlargement is not. Going up 10–20% is usually invisible. Doubling is a compromise. Quadrupling is a new image with made-up detail. The full explanation of why shrinking is safe and enlarging is not: resize images without losing quality. If you must enlarge, AI upscaling is the better of the imperfect options.
The far better answer is to go back to the original. The 800×600 file is usually a web copy of something that still exists at full size — in your camera roll, in an email, on the original card. Five minutes of looking beats any amount of processing.
Format and compression: invert your web instincts
Do not send a heavily compressed JPEG to print. On a screen, JPEG artefacts at quality 75 are essentially invisible. In print — especially at large sizes, on quality paper, with ink physically absorbing into the surface — the 8×8 block boundaries and the ringing around sharp edges can become genuinely visible. Print exposes compression damage that screens hide.
For print, use:
- TIFF or PNG where the printer accepts them — lossless, no artefacts, and the standard for professional work.
- JPEG at quality 90–100 if a JPEG is required. This produces a large file, and that is correct. File size is not a virtue here; there is no page load to worry about.
- PDF for anything with text or vector artwork, which keeps type crisp at any size.
Never send WebP or AVIF to a print shop. They are web delivery formats and most print workflows will not accept them.
And the same generation-loss warning as always: export from your original, never from a file that has already been compressed once. Print is exactly where accumulated damage becomes visible.
Colour: the other reason prints disappoint
Even at perfect resolution, printed colours can look duller than they did on screen. This is not a mistake — it is a real physical limitation.
Screens emit light and use RGB, mixing red, green, and blue. Printers absorb light and use CMYK ink. The two cover genuinely different ranges of colour, and CMYK's is smaller. Vivid, saturated blues, bright oranges, and neon greens are the usual casualties, because they sit outside what ink can physically reproduce and must be approximated by the nearest printable colour.
What to do about it:
- Ask the printer what they want. Many modern printers prefer to receive sRGB and handle the conversion themselves with a profile tuned to their machine and paper. Converting to CMYK yourself without knowing their profile can make things worse.
- Avoid extreme saturation in artwork destined for print, or accept that it will shift.
- Order a proof for anything that matters. A physical sample from the actual machine and paper is the only reliable preview.
- Do not trust an uncalibrated monitor. Most consumer displays run bright and saturated, which is precisely why prints so often feel flat by comparison.
Bleed, margins, and the edges of the page
If your image or background is meant to run right to the edge of the paper, it must extend beyond the final trim line. Printers cut through stacks of paper with a tolerance of a millimetre or two, and without that extra margin you get a thin white sliver along one edge.
The standard is 3 mm of bleed on every side (about 0.125 in in the US). So an A4 page designed as 210×297 mm should be supplied at 216×303 mm, with the understanding that the outer 3 mm will be trimmed away.
The corollary is a safe zone: keep text and anything important at least 3–5 mm inside the trim line, so a slight cutting drift never clips it. Between bleed and safe zone, the outer few millimetres of your design should contain background only.
A checklist before you send
- Confirm the final print size and the DPI your printer wants.
- Multiply to get required pixels — inches × DPI — and check your file meets or exceeds it.
- If it does not, find the original before considering upscaling.
- Crop to the correct aspect ratio so the printer is not making that decision for you. Paper ratios and camera ratios rarely match: a 3:2 photo does not fit a 4:5 frame without losing something, and you should choose what.
- Add bleed if anything runs to the edge, and keep text inside the safe zone.
- Export losslessly, or as JPEG at 90+ quality, from your original file.
- Ask about colour — send sRGB unless told otherwise, and expect saturated colours to soften.
- Order a proof for anything expensive or in volume.
Resizing, cropping, and converting for print all run locally in your browser on this site, which is worth noting when the files are client work or personal documents you would rather not hand to a third-party server. See in-browser image tools and privacy.
Common print jobs and what each one needs
Different products have genuinely different requirements, and knowing which you are dealing with saves a lot of back-and-forth with a printer.
Photo prints (4×6 up to 8×10). The straightforward case: 300 DPI, sRGB, JPEG at high quality is universally accepted. The main pitfall is aspect ratio — most cameras shoot 3:2, which fits 4×6 exactly but not 5×7 or 8×10. Crop deliberately or the lab will crop for you.
Photo books and albums. Usually laid out in the provider's own software, which will warn you when an image is too low-resolution for the slot you dropped it into. Take those warnings seriously; they are calculated from the actual placed size.
Canvas prints. More forgiving on resolution than paper, because the weave of the canvas itself hides fine detail and they are viewed from further away — 150 DPI is often sufficient. Less forgiving on composition: most canvases wrap around the frame edge, consuming 20–40 mm on every side. Anything near the border, especially faces, can disappear around the corner.
T-shirts and merchandise. Need a transparent background (PNG, not JPEG) and typically 300 DPI at the printed size. Fine detail and thin lines reproduce poorly on fabric, and colours shift noticeably depending on the garment colour underneath.
Business cards, flyers, and stationery. The bleed and safe-zone rules matter most here, because the design runs to the edge and the type sits close to it. Supply as PDF where possible so text stays vector-sharp rather than being rasterised.
Large-format posters and banners. Resolution requirements drop sharply with viewing distance, but file dimensions grow. Ask the printer for their preferred DPI at final size — supplying a billboard at 300 DPI produces a file nobody can open, let alone print.
Scanning and digitising for reprint
Reprinting an old photograph, a document, or a piece of artwork inverts the problem: instead of choosing a print size for a fixed number of pixels, you are choosing how many pixels to capture. The same formula governs it.
Scan at the DPI you need for the output size, not the input size. If you are scanning a 4×6 photo and only ever reprinting it at 4×6, scanning at 300 DPI is sufficient. If you want to enlarge it to A4 — roughly double in each dimension — you need to scan at 600 DPI to end up with enough pixels at the larger size. Scanning is the one moment when detail is genuinely free to capture, and the one moment you cannot go back and redo without finding the physical original again.
Scan to a lossless format. TIFF or PNG for the master copy. A scanner set to output JPEG at default quality bakes compression artefacts into an image you may want to work on later, and those artefacts amplify under any subsequent enlargement.
Photographing a document instead of scanning it is workable when it is flat, evenly lit, and shot straight-on, but it introduces perspective distortion and uneven lighting that a scanner does not. If it is going to print, scan it.
Old prints carry their own texture. Photographic paper has a surface — often visibly patterned on prints from the 1970s and 80s — and scanning at high DPI captures that texture along with the image. This is normal, and mostly disappears at ordinary viewing distance in the reprint.
Frequently asked questions
What DPI should I use for printing? 300 DPI for anything held and read at normal distance. Posters viewed from a metre or more are fine at 150–200, and large-format banners need far less. Viewing distance sets the requirement, not the paper.
Does changing the DPI setting improve my image quality? No. DPI is metadata describing how densely to print existing pixels. Changing it without changing the pixel count only changes the intended print size — the image data is identical.
How big can I print a phone photo? A 12 MP photo (about 4000×3000 px) prints cleanly at A4 at 300 DPI and comfortably at A3 at a slightly lower density. The usual obstacle is that the file on hand is a web-shrunk copy rather than the camera original.
Why does my print look duller than my screen? Screens emit light using RGB; printers absorb it using CMYK ink, which covers a smaller range of colours. Saturated blues, oranges, and neon greens sit outside what ink can reproduce and get approximated. Most consumer monitors are also uncalibrated and run bright.
Should I convert to CMYK before sending? Ask the printer. Many modern shops prefer sRGB and convert using a profile matched to their specific machine and paper, which produces better results than a generic conversion done blind.
What is bleed and do I need it? Extra image extending past the trim line — normally 3 mm on each side — so that cutting tolerance never leaves a white sliver at the edge. You need it whenever colour or imagery runs to the edge of the paper. You do not if the design sits inside a white margin.
Can I use a WebP or AVIF file for printing? No. Those are web delivery formats and print workflows generally will not accept them. Supply TIFF, PNG, high-quality JPEG, or PDF.
Key takeaways
- DPI is not stored quality — it is a statement of how densely to pack existing pixels. Pixels = inches × DPI.
- 300 DPI is the standard for hand-held reading, but posters need 150–200 and billboards far less. Viewing distance sets the requirement.
- A 12 MP phone photo is plenty for A4 or A3. The usual problem is that the file was shrunk for the web, not that the camera was insufficient.
- Upscaling invents detail that was never captured. Small enlargements are fine; large ones are a compromise. Find the original instead.
- Invert your web habits: use lossless formats or JPEG at 90+, never WebP or AVIF, and do not optimise for file size.
- RGB screens can show colours CMYK ink cannot print — saturated blues and neons will shift. Ask the printer about colour handling and order a proof.
- Add 3 mm of bleed for edge-to-edge artwork and keep text well inside the trim line.