DPI converter · lossless by default
Change image DPI without resampling it
Set 300, 600, or any value on JPEG, PNG, BMP and TIFF files. The default mode rewrites the resolution tag and copies your pixels exactly, then reads the file back before the download unlocks.
Batch converter
No files yet
Drop images to set their DPI
JPEG · PNG · BMP · TIFF · up to 30 files · 100 MB each
Nothing is uploaded. Metadata is read and rewritten inside this tab.
01
What changes
Pixel width divided by target DPI gives print width. The pixels stay where they are.
DPI in an image file is a label that tells print software how densely to place the pixels it already has. Changing it does not stretch, sharpen or redraw anything. A 3000 px wide photo printed at 300 DPI is 10 inches wide. Set the same file to 150 DPI and it prints 20 inches wide from the same pixels, with half the density.
That is why this converter defaults to tag-only. It edits the resolution blocks, leaves the compressed image data alone, and keeps the rest of the file intact. The output is the same picture with a different print instruction. If you need more pixels than the file holds, the guide explains when resampling helps and when it cannot.
02
How the converter works
The file is parsed, patched, then parsed again.
- 01
Read every resolution block
The parser inspects the file signature, then the format-specific headers: JFIF and EXIF in JPEG, pHYs in PNG, the DIB header in BMP, and the IFD tags in TIFF. If two blocks disagree, both values are shown.
- 02
Write one value, in place
The target DPI replaces the existing value where a block already exists. JPEG and PNG get a new block when the file never had one. New EXIF entries are inserted with corrected offsets so thumbnails, MakerNotes and sub-IFDs still resolve after the edit.
- 03
Read the saved bytes back
The output is parsed again from scratch. If any resolution block is missing the target value, or differs by more than one DPI, the download stays locked and the report says which block failed.
03
Which DPI fits the job
Common presets and what each one is for.
| Value | Typical use | What it means |
|---|---|---|
| 72 DPI | Web and screen exports | A legacy default, not a rule. Same pixels print fine at 300 DPI. |
| 150 DPI | Draft prints, large banners | Acceptable at viewing distance; visibly softer up close. |
| 300 DPI | Photo prints, books, POD | The common submission standard for continuous-tone images. |
| 600 DPI | Line art, scans, fine art | Useful only when the file genuinely holds that much detail. |
04
Check a print size before you commit
A DPI tag does not guarantee a sharp print. The pixel count has to support the paper size.
| Print size | At 150 DPI | At 300 DPI | At 600 DPI |
|---|---|---|---|
| 4 × 6 in | 600 × 900 | 1,200 × 1,800 | 2,400 × 3,600 |
| 5 × 7 in | 750 × 1,050 | 1,500 × 2,100 | 3,000 × 4,200 |
| 8 × 10 in | 1,200 × 1,500 | 2,400 × 3,000 | 4,800 × 6,000 |
| A4 | 1,241 × 1,754 | 2,481 × 3,508 | 4,962 × 7,016 |
| US Letter | 1,275 × 1,650 | 2,550 × 3,300 | 5,100 × 6,600 |
| 2 × 2 in photo | 300 × 300 | 600 × 600 | 1,200 × 1,200 |
Largest print at 300 DPI
6.67 × 10.00 in
16.9 × 25.4 cm · 6.0 MP
Thin at this size
At 8.00 × 10.00 in the file resolves to about 250 DPI. That is 83% of the pixels a clean print needs.
- Pixels needed for this print
- 2400 × 3000 px
- Pixels you have
- 3000 × 2000 px
The calculation matches the verdict shown on each file card. A result above 300 effective DPI is more than enough; between 150 and 300 is printable but soft; below 150 will show on paper regardless of the tag.
05
Format support
DPI storage varies by format. These are the paths this tool takes.
| Format | Where DPI lives | Tag-only edit | Notes |
|---|---|---|---|
| JPEG | JFIF density + EXIF X/Y | Yes | Both blocks are set to the same value. APP2 and other segments are untouched. |
| PNG | pHYs chunk | Yes | pHYs is inserted before IDAT and its CRC is recomputed. |
| BMP | Header pixels-per-meter | Yes | Stored at byte 38 and 42 of the DIB header. |
| TIFF | IFD tags 282, 283, 296 | Yes | Multi-page files are patched on every page. |
| WebP | EXIF chunk, best effort | Re-encodes | Reading works; writing goes through the canvas and loses metadata. |
| HEIC / AVIF | ISO BMFF properties | Converts | Output is PNG or JPG because browsers rarely encode HEIC. |
| GIF / ICO / SVG | None or vector | No | GIF has no DPI field; vector files do not have a fixed resolution. |
JPG and PNG are the safe choices for print submissions. BMP and TIFF are supported at the same level because their headers are unambiguous. WebP and AVIF can be read with confidence but cannot be written losslessly in a browser, so the converter re-encodes them and tells you so before you download. GIF files carry no DPI field at all; ICO and SVG are left out on purpose.
06
Resampling cannot add detail
Raising the tag does not create pixels.
For a real enlargement, start from the largest original you can find, then choose resample mode deliberately. The output is re-encoded, EXIF is lost, and the file grows. The increase-DPI guide covers the desktop and command-line routes as well, including the cases where a 72 DPI file is already print-ready.
Colour work is separate. This tool does not convert RGB to CMYK, because the browser canvas is RGB-only and a naive conversion shifts colour. Ask your print lab which profile they expect and convert in a colour-managed application.
Questions people ask
Short answers to the questions that come up most often after a DPI edit.
Does changing DPI affect image quality?
Not in the default tag-only mode. The converter rewrites resolution metadata and copies every pixel without recompressing it, so the visible image is unchanged. Quality only changes if you choose the resample mode, which creates new interpolated pixels.
How do I change an image to 300 DPI?
Drop the file above, pick 300 from the target presets, leave the mode on tag-only, and press Convert. The tool writes 300 DPI into every resolution block the format supports, reads the file back, and enables the download only if the new value verifies.
What is the difference between DPI and PPI?
PPI counts image pixels per inch; DPI counts printer dots per inch. Image files store a resolution value that print software interprets as PPI, but most apps and print labs label it DPI anyway. For the purposes of this tool the two are the same number.
My image is 72 DPI. Will it look bad in print?
The tag alone does not decide that. A 3000 × 2000 px file tagged 72 DPI still contains 3000 × 2000 px. Set it to 300 DPI and it prints at 10 × 6.67 inches with full detail. A 720 × 720 px file tagged 300 DPI is still only 720 px wide and will look soft at 10 inches.
Does this tool upload my images?
No. Files are read with the browser File API and processed inside this tab; nothing is sent to a server. You can load the page, switch off your network, and convert files. Only the page itself was downloaded.
Which formats keep their pixels exactly the same?
JPEG, PNG, BMP and TIFF are edited at the byte level. Pixel data, EXIF camera information, ICC profiles and thumbnails are left in place. WebP and AVIF are detected and read, but writing DPI requires re-encoding; HEIC is read and converted to PNG or JPG.
Can I change the DPI of a PDF here?
Not yet. PDF DPI is a rendering instruction applied by the PDF viewer or printer, not a single tag inside the file. A page-level PDF tool is planned for a later release; it is not part of this version.
Is 600 DPI better than 300 DPI?
Only when the pixel count supports it and the output needs it. Most photo labs and print-on-demand services want 300 DPI. Line art, film scans and some fine-art printers benefit from 600 DPI. A label of 600 DPI cannot add detail that the pixels do not contain.