72 → 300 · the arithmetic
72 DPI to 300 DPI: what changes
Raising the tag from 72 to 300 DPI makes the same pixels print 4.17 times smaller. That suits a lab submission but not a poster. The sections below show which result your file needs, and why the tag change alone does not add quality.
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Start with tag-only. If you need the same physical size at 300 DPI, switch to resample and accept interpolated pixels.
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01
The 4.17× rule
300 ÷ 72 = 4.1667. The pixel count stays the same.
| Pixels | Print at 72 DPI | Print at 300 DPI |
|---|---|---|
| 720 × 720 px | 10 × 10 in | 2.40 × 2.40 in |
| 1080 × 1080 px | 15 × 15 in | 3.60 × 3.60 in |
| 1920 × 1080 px | 26.67 × 15 in | 6.40 × 3.60 in |
| 3000 × 2000 px | 41.67 × 27.78 in | 10 × 6.67 in |
| 6000 × 4000 px | 83.33 × 55.56 in | 20 × 13.33 in |
A file with 720 pixels across covers ten inches at 72 DPI and 2.4 inches at 300 DPI. The pixel count is the same; only the density changed. If the lab asked for a ten-inch print at 300 DPI, you need 3000 pixels across; the tag change alone gives you a small print instead.
02
Which result do you want?
The same button produces two different files, so decide which output you need first.
You want the tag fixed
The file already has enough pixels; 72 is just a leftover export value. A 3000 × 2000 px image from a camera or a design export often lands in this category. Set it to 300 DPI and it prints at 10 × 6.67 inches with every pixel intact. This is the common case for photos that came through a web export or an old layout template.
You want the physical size kept
The file is being enlarged to fill a specific sheet, and you accept new pixels. A 720 × 720 px web graphic that must become a 10 × 10 inch print needs 3000 × 3000 px. Resample mode does the 4.17× enlargement in one pass. The canvas then holds 9 megapixels, while the recorded detail still amounts to the original 0.5 megapixels.
You are not printing at all
Then leave the tag alone. Browsers ignore it. If a client's upload form insists on 300 DPI, a tag-only pass satisfies the form without touching the image.
03
Doing it here
Three decisions, then a verified download.
- 01
Choose the target and the mode
300 DPI is already selected. Leave the mode on tag-only if the pixels are enough; choose resample if the print size must stay the same. The options panel explains what each mode writes.
- 02
Compare the before and after numbers
Each file card shows the embedded DPI, the pixel dimensions, the largest print at the target, and a verdict against your paper size. A 72 DPI file with plenty of pixels will pass; a thin file will warn before you spend money on a print.
- 03
Download and keep the original
The download unlocks only after the output is parsed again and every resolution block reads 300 DPI. The filename gains a _300dpi suffix by default so the tagged copy is easy to tell apart from the web original.
04
What resampling cannot fix
Interpolation estimates pixels that were never recorded.
- Missing detail. If the eyelashes were not recorded, no algorithm can place them back. Interpolation averages neighbouring pixels and invents a smooth value between them.
- Text and line art. Edges soften first. A logo or a scanned document enlarged from a 72 DPI screen capture will look fuzzy, even at 300 DPI, because the original edge information is gone.
- JPEG artefacts. A low-quality JPEG has blocky compression noise. Enlarging magnifies it, and re-encoding can add another layer.
- Camera metadata. The redrawn file loses EXIF, GPS and the embedded thumbnail. Keep the original if those matter for licensing or archival.
AI upscalers can produce a more convincing enlargement than a bicubic filter, but they are synthesising detail rather than restoring it. For editorial, judicial or scientific use, that difference should be disclosed. The increase-DPI guide covers the desktop workflows and when each one is defensible.
05
Verify before the lab does
Two checks: the tag, and the print size.
Run the converted file through the DPI checker. It should report 300 DPI in every block, with no conflicting value left at 72. Then divide the pixel dimensions by 300 to confirm the physical size matches the order. If the result says 2.4 × 2.4 inches and you ordered 10 × 10, the file needs pixels, not a different tag.
For an expensive print, order a small proof first. Screen previews hide paper texture, softness and colour shifts, and a $3 proof is cheaper than a reprinted canvas.
Questions people ask
The questions that come up whenever someone moves a file from 72 to 300.
Is going from 72 DPI to 300 DPI just a tag change?
In tag-only mode, yes. The pixel grid is untouched; only the print instruction changes. The same 3000 pixel wide image that printed at 41.7 inches tagged 72 DPI now prints at 10 inches tagged 300 DPI.
Does converting from 72 to 300 DPI improve image quality?
No. A tag change cannot add detail. Quality improves only if the original pixels were sufficient and the old tag was forcing them to spread over too much paper. Resampling adds pixels by interpolation, which can smooth an enlargement but cannot recover detail that was never captured.
Why does the print size change by 4.17 times?
Because 300 divided by 72 is 4.1667. At 300 DPI each inch of paper receives 4.17 times as many pixels as it did at 72 DPI. With a fixed pixel count, the paper must therefore be 4.17 times smaller in each direction.
My image is 1920 × 1080 px at 72 DPI. Can I print A4 at 300 DPI?
Not cleanly. A4 at 300 DPI needs about 2481 × 3508 pixels. Your file has 1920 × 1080, so it fills A4 at roughly 92 to 232 DPI depending on orientation: soft, especially up close. At 300 DPI it prints about 6.4 × 3.6 inches. For A4, start from a larger original or accept a lower-density print.
Can I set 300 DPI and keep the same print size?
Only by adding pixels. Keeping a 720 × 720 px image at 10 inches and raising it from 72 to 300 DPI would require 3000 × 3000 px. The converter’s resample mode does that by interpolation, and it caps the output at 100 megapixels.
Does DPI matter for images on a website?
No. Browsers lay out images by CSS pixel dimensions and ignore the embedded DPI tag. A 72 DPI and a 300 DPI copy of the same pixels display identically. DPI only becomes relevant when the image is sent to a printer or placed in page-layout software.
Does resampling delete EXIF data?
In this browser tool, yes. The image is redrawn on a canvas and re-encoded, so camera metadata, GPS and the original thumbnail do not survive. The new file does get the correct 300 DPI tag, and the read-back step confirms it before download.