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Resize a photo to 30×40 mm (354×472 pixels)
A 30×40 mm print at 300 DPI is 354×472 pixels. Set 30×40 mm and 300 DPI in the panel and choose crop to fill: a 4:3 phone photo loses 43.8% and still gives 1,920 pixels per inch. As a JPEG, a head-and-shoulders portrait comes to about 33.5 KB at the panel's default quality 85 and 25.6 KB at quality 75.
30×40 mm at 300 DPI (354×472 px)
JPG · no file-size limit · 30x40 mm at 300 DPI · white background
No file-size limit is set: PixelFit saves at high quality and changes only the format and any pixel size you set. 30x40 mm at 300 DPI is 354x472 pixels.
Fit, background and padding crop to fill · white background
Saving presets is part of Pro.
The result appears here: the exact byte count, pixel size and quality, the size before and after, a preview and a download button.
The batch kit (one ZIP for up to 500 photos, several photos merged into one PDF) is part of Pro.
30×40 mm at a glance
| Physical size | 30×40 mm = 1.18×1.57 in |
|---|---|
| Pixels at 300 DPI | 354×472 px (167,088 pixels, 0.17 MP) |
| Shape | 3:4, portrait (width ÷ height = 0.75) |
| From a 12 MP phone photo | 1,920 pixels per inch after the crop to fill (43.8% cut) |
| Copies per sheet | 10 on 4×6 in · 49 on A4 · 45 on US Letter |
| At 600 DPI | 709×945 px (0.67 MP) |
| Resampling passes from a phone photo | 2268×3024 crop → 1134×1512 → 567×756 → 354×472 |
| Estimated JPEG (portrait photo, quality 75, 300 DPI) | 25.6 KB |
| JPEG without a KB limit (panel default, quality 85) | 33.5 KB |
How 30×40 mm turns into pixels
An inch is exactly 25.4 mm, so at 300 DPI the pixel size is 30 mm ÷ 25.4 × 300 = 354.331, rounded to 354 px wide, and 40 mm ÷ 25.4 × 300 = 472.441, rounded to 472 px tall. 30×40 mm is a portrait shape with sides in the ratio 3:4 (0.75 as a decimal), 1.18×1.57 in in the other unit.
The same 30×40 mm needs 236×315 px at 200 DPI and 709×945 px (0.67 MP) at 600 DPI. PixelFit writes the DPI you set into the JPEG header (the JFIF density field), so print software that reads it knows the file is meant to come out at 30×40 mm.
Is your photo sharp enough for 30×40 mm?
After the crop to fill, this is how many source pixels land on each inch of 30×40 mm. Above 300 DPI the picture is reduced to 300 DPI; below it, PixelFit has to enlarge the crop and fine detail softens.
| Starting image | Crop to fill keeps | Area lost | Pixels per inch at 30×40 mm | To reach 300 DPI |
|---|---|---|---|---|
| 12 MP phone photo (4032×3024, 4:3) | 2268×3024 (left and right cut) | 43.8% | 1,920 DPI | reduced (0.16×) |
| 24 MP camera photo (6000×4000, 3:2) | 3000×4000 (left and right cut) | 50% | 2,540 DPI | reduced (0.12×) |
| Full HD screenshot (1920×1080, 16:9) | 810×1080 (left and right cut) | 57.8% | 686 DPI | reduced (0.44×) |
| Vertical phone video frame (1080×1920, 9:16) | 1080×1440 (top and bottom cut) | 25% | 914 DPI | reduced (0.33×) |
30×40 mm in pixels at each print resolution
Pixels = millimetres ÷ 25.4 × DPI. The panel uses 300 DPI unless you change it; the file sizes are for a portrait saved as JPEG.
| Resolution | Pixels | Megapixels | JPEG q75 | JPEG q90 |
|---|---|---|---|---|
| 150 DPI | 177×236 | 0.0418 MP | ≈ 9.5 KB | ≈ 14.9 KB |
| 200 DPI | 236×315 | 0.0743 MP | ≈ 14.2 KB | ≈ 22.7 KB |
| 300 DPI | 354×472 | 0.17 MP | ≈ 25.6 KB | ≈ 41.5 KB |
| 400 DPI | 472×630 | 0.3 MP | ≈ 39.3 KB | ≈ 64.7 KB |
| 600 DPI | 709×945 | 0.67 MP | ≈ 73.1 KB | ≈ 125 KB |
Will a 30×40 mm photo fit a KB limit?
Saved at 300 DPI (354×472 px), a head-and-shoulders portrait of 30×40 mm comes to about 20 KB at JPEG quality 60, 25.6 KB at 75 and 41.5 KB at 90, and about 16.5 KB as WebP at 75. Dropping to 200 DPI (236×315 px) brings quality 75 down to about 14.2 KB, but the print then holds fewer pixels per inch.
At 300 DPI the photo fits under 20 KB up to quality 58 and under 50 KB up to quality 92; under 100 KB and 200 KB it fits even at quality 95. Set the KB limit next to the size and PixelFit picks the highest quality that fits.
Printing 30×40 mm copies
Without margins or cutting gaps, 10 copies fit on one 4×6 in (102×152 mm) photo print, 49 on an A4 sheet, 45 on US Letter (some turned sideways where that packs more). Print at 100% scale, never "fit to page", or a small ID photo of 30×40 mm comes out the wrong size; 354×472 px at 300 DPI is exact.
Other 3:4 print and photo sizes
These sizes have the same 3:4 shape as 30×40 mm, so a photo cropped for one fits the others with no further crop.
| Size | Pixels | Scale from 30×40 mm |
|---|---|---|
| 300×400 portrait | 300×400 | 0.85× |
| 480×640 portrait | 480×640 | 1.36× |
| 600×800 portrait | 600×800 | 1.69× |
| 768×1024 portrait | 768×1024 | 2.17× |
| 150×200 px photo | 150×200 | 0.42× |
| 900×1200 portrait | 900×1200 | 2.54× |
| 1080×1440 portrait | 1080×1440 | 3.05× |
| 1200×1600 portrait | 1200×1600 | 3.39× |
How to resize a picture to 30×40 mm
-
Add the picture
Drop, paste or pick the photo in the PixelFit panel at the top of this page; it is decoded in your browser and never uploaded.
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Set the size
Pick mm as the unit, enter 30×40 mm and 300 DPI; the tool turns that into 354×472 pixels.
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Choose how it fits
Choose crop to fill to keep the 3:4 frame without stretching (a phone photo loses 43.8%, left and right cut). Fit inside keeps the whole picture as a 354×266 file instead; Pad with colour puts that on a full 354×472 canvas.
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Pick the format and download
Keep JPG (without a KB limit PixelFit saves at quality 85, about 33.5 KB for a head-and-shoulders portrait) so the 300 DPI stamp travels with the file, or choose PDF to get the picture as a PDF page, then download.
Sources
- Inch (1 inch is exactly 25.4 mm), Wikipedia, checked 31 October 2026: en.wikipedia.org/wiki/Inch
- Measured by PixelFit with sharp 0.35.5 / libvips 8.18.7 on 31 October 2026, from the sample photo President Barack Obama.jpg by Pete Souza (Official White House photo) (Public domain): commons.wikimedia.org/wiki/File:President_Barack_Obama.jpg
Frequently asked questions
How do I resize a photo to 30×40 mm?
Open the photo in the PixelFit panel on this page, set 30×40 mm at 300 DPI (354 × 472 px), choose crop to fill and download. From a 12 MP phone photo that crops 43.8% (left and right cut) and still leaves 1,920 pixels per inch to work with.
How many pixels is 30×40 mm?
30×40 mm is 354×472 px at 300 DPI, 709×945 px at 600 DPI and 177×236 px at 150 DPI (pixels = mm ÷ 25.4 × DPI).
What DPI should a 30×40 mm photo have?
PixelFit uses 300 DPI, which makes 30×40 mm exactly 354×472 px; print it at 100% scale. At 150 DPI the same 354×472 pixels would print 2.36×3.15 in, twice as large and with half the density.
How many 30×40 mm photos fit on one sheet?
Without margins, 49 fit on A4 (210×297 mm), 45 on US Letter and 10 on a 4×6 in photo print, turning them sideways where that packs more. Leave a few millimetres for cutting.
How big is a 30×40 mm JPEG at 300 DPI?
For a head-and-shoulders portrait about 25.6 KB at quality 75 (20 KB at 60, 41.5 KB at 90, 33.5 KB at the panel's default quality 85); a detailed outdoor photo is about 41.9 KB at quality 75, estimated from measured encodes of real sample photos at 354×472 px.
Related
Same 3:4 ratio
Nearby sizes
- 400×514 px photo 200:257 (about 7:9)
- 35×45 mm passport photo 7:9
- 420×540 px photo 7:9
- 420×525 px photo 4:5
- 25×35 mm photo 5:7
- 33×48 mm photo 130:189 (1:1.45)