What the DPI setting actually does
A print shop or publisher asking for "a 300 DPI TIFF" is really asking two things: that the file is a TIFF, and that it has enough pixels to print at the size they need. The DPI number inside the file is only a label. It tells the printer how many pixels to squeeze into each inch, so it decides the printed size, but it doesn't add or remove a single pixel. That's why this converter never resamples: the pixels go across exactly as they are, and each result tells you how large it will print.
| Image size in pixels | At 300 DPI it prints at | At 150 DPI |
|---|---|---|
| 4032 × 3024 (12 MP phone photo) | 13.4 × 10.1 in (34.1 × 25.6 cm) | 26.9 × 20.2 in |
| 2048 × 1536 | 6.8 × 5.1 in (17.3 × 13 cm) | 13.7 × 10.2 in |
| 1200 × 1800 | 4 × 6 in, a standard photo print | 8 × 12 in |
| 2400 × 3000 | 8 × 10 in | 16 × 20 in |
| 2480 × 3508 | A4 (21 × 29.7 cm) | A3 |
So if a magazine wants a photo at 8 × 10 inches and 300 DPI, the image needs to be at least 2400 × 3000 pixels before it is converted. Typing "600" into a converter won't get you there: it simply makes the same picture print half as wide. By default this tool keeps the DPI already stored in your JPG (from its JFIF header or EXIF data), and if the file has none, it writes 72, the value most software assumes anyway.
Converting won't add quality, and it costs space
TIFF is lossless, which means it stores the picture it is given without changing it. It can't restore detail that JPEG compression already threw away. We checked this on a 2048 × 1536 photo: the TIFF decoded to exactly the same pixels as the JPG, with a difference of zero, compression blocks included. What did change was the size:
| Same photo, 2048 × 1536 | File size | vs the JPG |
|---|---|---|
| Original JPG (quality 90) | 1.19 MB | — |
| TIFF, ZIP (Deflate) | 5.55 MB | 4.7× larger |
| TIFF, LZW | 6.34 MB | 5.3× larger |
| TIFF, uncompressed | 9.44 MB | 7.9× larger |
The real reason to convert is that the recipient's workflow requires TIFF: a print shop or photo lab, a publisher or a stock library, an archive, or a scanning and fax system. Converting also stops further loss if you plan to keep editing the image, because every re-save of a JPG compresses it again. If you just need a smaller file, go the other way with TIFF to JPG.
LZW, ZIP or uncompressed?
All three are lossless: in our test the three TIFFs held byte-for-byte identical pixels. The difference is size and compatibility. LZW is the safe default: it is the most widely supported lossless option, offered by Photoshop and accepted by print shops. ZIP came out about an eighth smaller in our test and is read by Photoshop, GIMP, macOS and Windows. Uncompressed is for the occasional older RIP, fax gateway or upload system that only accepts plain TIFF. Both compressed options use the standard "horizontal differencing" predictor, which shrinks photos noticeably. We opened all three files with libtiff and with the Windows imaging component, and both read the image, the 300 DPI setting and the colour profile.
The colour profile comes along
Many JPGs carry an embedded colour profile that says how their numbers should be read. iPhones, for instance, shoot in the wider Display P3 colour space and say so in the file. Drop that profile and the same pixels get read as ordinary sRGB, so reds and greens look duller. This converter copies the profile into the TIFF unchanged, and the result line names it. A greyscale TIFF can't use an RGB profile, so in that case it is left out and the result says so.
This tool doesn't produce CMYK TIFFs, on purpose. Turning screen colours into ink is done properly with the profile of the press that will print the job, and print shops usually prefer to do it themselves. A quick generic formula can be far off: when we measured it on a print photo for our PSD to JPG converter, the formula was off by 24 out of 255 levels on average. Send RGB unless the shop tells you otherwise, and ask which profile they want.
Several JPGs in one multi-page TIFF
Fax services, document management systems and some court and insurance portals want a document as a single multi-page TIFF. Add the scans, put them in order with the arrows or by dragging, and choose One multi-page TIFF. Each page keeps its own size and DPI. If the portal also accepts PDF, JPG to PDF gives a much smaller file.
Transparency and greyscale
PNG and WebP images work too. Transparent areas are filled with white, because a lot of print software mishandles TIFFs with an alpha channel, and the result tells you how many pixels were affected. The greyscale option stores one channel instead of three, a third of the data, and is what many document archives ask for.
Every file is read back and checked
Browsers have no built-in way to save a TIFF, so this page writes the file itself. To make sure nothing went wrong, it then decodes each finished TIFF and compares it with the original, pixel by pixel, before you download it. The result line says "every pixel matches", or tells you exactly what differs. Everything happens in your browser: the images are never uploaded, so it's fine for unpublished work and scanned documents, and there's no account or limit.