How many pixels are in an inch?
On the web, an inch is exactly 96 pixels, because CSS defines 1in = 96px. In print there is no fixed number: an inch holds as many pixels as the DPI you print at, so 300 pixels at 300 DPI, 150 at 150 DPI and 72 at 72 DPI.
US Letter (8.5 × 11 in) is 2550 × 3300 pixels at 300 DPI and 816 × 1056 at 96.
The formula
A pixel has no physical size until you decide how many go into an inch. That number is the DPI (dots per inch), also called PPI (pixels per inch); this guide uses one number for both. Once you pick it, the conversion is one step:
pixels = inches × DPI
inches = pixels ÷ DPI
centimetres = inches × 2.54
The 2.54 is exact: the W3C's CSS units define 1 in as 2.54 cm.
Pixels per inch, centimetre and millimetre
At a given DPI, an inch is simply that many pixels. Centimetres and millimetres follow from 1 in = 2.54 cm = 25.4 mm.
| DPI | Pixels per inch | Pixels per cm | Pixels per mm |
|---|---|---|---|
| 72 | 72 | 28.35 | 2.83 |
| 96 | 96 | 37.80 | 3.78 |
| 150 | 150 | 59.06 | 5.91 |
| 300 | 300 | 118.11 | 11.81 |
| 600 | 600 | 236.22 | 23.62 |
Pixels per cm and per mm are rounded to 2 decimals.
8.5 x 11 in pixels
US Letter is 8.5 × 11 inches. Multiply both sides by the DPI:
| DPI | Working | Pixels (portrait) |
|---|---|---|
| 72 | 8.5 × 72, 11 × 72 | 612 × 792 |
| 96 | 8.5 × 96, 11 × 96 | 816 × 1056 |
| 150 | 8.5 × 150, 11 × 150 | 1275 × 1650 |
| 200 | 8.5 × 200, 11 × 200 | 1700 × 2200 |
| 300 | 8.5 × 300, 11 × 300 | 2550 × 3300 |
| 600 | 8.5 × 600, 11 × 600 | 5100 × 6600 |
For landscape, swap the two numbers: 3300 × 2550 at 300 DPI.
Other paper and photo sizes in pixels
Paper dimensions are the W3C's CSS page sizes. Metric sizes don't land on whole pixels, so they're rounded to the nearest pixel; A4 at 300 DPI is exactly 2480.31 × 3507.87.
| Size | 300 DPI | 150 DPI | 96 DPI | 72 DPI |
|---|---|---|---|---|
| Letter, 8.5 × 11 in | 2550 × 3300 | 1275 × 1650 | 816 × 1056 | 612 × 792 |
| Legal, 8.5 × 14 in | 2550 × 4200 | 1275 × 2100 | 816 × 1344 | 612 × 1008 |
| Ledger, 11 × 17 in | 3300 × 5100 | 1650 × 2550 | 1056 × 1632 | 792 × 1224 |
| A5, 148 × 210 mm | 1748 × 2480 | 874 × 1240 | 559 × 794 | 420 × 595 |
| A4, 210 × 297 mm | 2480 × 3508 | 1240 × 1754 | 794 × 1123 | 595 × 842 |
| A3, 297 × 420 mm | 3508 × 4961 | 1754 × 2480 | 1123 × 1587 | 842 × 1191 |
| 4 × 6 in photo | 1200 × 1800 | 600 × 900 | 384 × 576 | 288 × 432 |
| 5 × 7 in photo | 1500 × 2100 | 750 × 1050 | 480 × 672 | 360 × 504 |
| 8 × 10 in photo | 2400 × 3000 | 1200 × 1500 | 768 × 960 | 576 × 720 |
Pixels to inches: worked examples
Going the other way, divide the pixels by the DPI.
| Image width | DPI | Working | Inches | Centimetres |
|---|---|---|---|---|
| 1200 px | 300 | 1200 ÷ 300 | 4 | 10.16 |
| 3000 px | 300 | 3000 ÷ 300 | 10 | 25.4 |
| 4032 px | 300 | 4032 ÷ 300 | 13.44 | 34.138 |
| 4032 px | 150 | 4032 ÷ 150 | 26.88 | 68.275 |
| 1920 px | 96 | 1920 ÷ 96 | 20 | 50.8 |
| 1080 px | 96 | 1080 ÷ 96 | 11.25 | 28.575 |
So a 4032 × 3024 photo prints at 13.44 × 10.08 in at 300 DPI. Halve the DPI and the print doubles in each direction, with each pixel twice as wide.
Why the web says an inch is 96 pixels
The W3C's CSS Values and Units specification fixes the absolute units to each other: 1in = 2.54cm = 96px, so 1px is 1/96 of an inch and 1pt is 1/72 of an inch. That makes a CSS point 96 ÷ 72 = 1.333 pixels and a CSS centimetre 96 ÷ 2.54 = 37.795 pixels.
That CSS pixel is a "reference pixel", not a dot on your screen. The specification recommends that screens anchor the units to the pixel, so a CSS inch is always 96 CSS pixels which need not match an inch measured on the glass. For print, it recommends anchoring to physical units, so a CSS inch prints as a real inch.
| CSS unit | Definition | In CSS pixels |
|---|---|---|
| 1in | 2.54cm | 96 |
| 1cm | 96px ÷ 2.54 | 37.795 |
| 1mm | 1/10 of 1cm | 3.780 |
| 1pt | 1/72 of 1in | 1.333 |
| 1pc | 1/6 of 1in | 16 |
Changing the DPI doesn't add pixels
The DPI number stored in a photo is a label. Changing it without resizing keeps every pixel and only changes the size an app suggests when you print, by the formula above: the same 3000 px is 10 in at 300 DPI or 20 in at 150 DPI. To print bigger at the same DPI, you need an image with more pixels.
If a print shop or printer gives you a DPI, use theirs. Work out the pixels you need for the print size, then check your image has at least that many.
Do it with the free converter
The Pixels to Inches Converter does this maths for any size and DPI, in inches, centimetres or millimetres. Drop in a photo and it reads the pixel size on your device and shows how big it prints at 72, 96, 150, 300 and 600 DPI.
Open Pixels to InchesFAQ
Is 1 inch always 96 pixels?
Only in CSS. The W3C defines a CSS inch as 96 CSS pixels. A photo has no size in inches until you pick a DPI, and then an inch is that many pixels: 300 at 300 DPI.
How many pixels is 1 inch at 72 DPI?
72 pixels. At 72 DPI each inch is 72 pixels wide, so 8.5 × 11 in is 612 × 792 px.
How do I convert pixels to inches?
Divide the pixels by the DPI: inches = pixels ÷ DPI. 3000 px at 300 DPI is 10 in. For the web, use 96, the number of CSS pixels in a CSS inch.
What is 300 pixels in inches?
It depends on the DPI. 300 px is 1 in at 300 DPI, 2 in at 150 DPI, 3.125 in at 96 DPI (a CSS inch) and about 4.17 in at 72 DPI.
What size is 1920 x 1080 pixels in inches?
At 96 DPI, the CSS ratio, it's 20 × 11.25 in. Printed at 300 DPI it's 6.4 × 3.6 in, and at 72 DPI about 26.67 × 15 in. On a monitor, how many inches it covers depends on the size of that screen, not on the pixel count.
What is 8.5 x 11 in pixels at 300 DPI?
2550 × 3300 pixels: 8.5 × 300 = 2550 and 11 × 300 = 3300. At 150 DPI it's 1275 × 1650.
How many pixels is A4?
A4 is 210 × 297 mm. At 300 DPI that's 2480.31 × 3507.87, which rounds to 2480 × 3508 pixels. At 96 DPI it's 794 × 1123.
How many pixels are in a centimetre?
Divide the DPI by 2.54. At 300 DPI a centimetre is 118.11 pixels; in CSS (96 per inch) it's 37.795.
What's the difference between DPI and PPI?
PPI is pixels per inch; DPI is dots per inch, a printing term. When you convert between pixels and inches you need one number of pixels per inch, and this page calls it DPI.
Related
Sources
Each page below was read on 27 October 2026.
- W3C, CSS Values and Units Module Level 4, §6.2 Absolute lengths. 1in = 2.54cm = 96px, 1px = 1/96th of 1in, 1pt = 1/72nd of 1in, the reference pixel, and anchoring to the pixel on screens and to physical units in print. Working Draft, 12 March 2024.
- W3C, CSS Paged Media Module Level 3, §7.1 Page size. Paper sizes: letter 8.5 × 11 in, legal 8.5 × 14 in, ledger 11 × 17 in, A5 148 × 210 mm, A4 210 × 297 mm, A3 297 × 420 mm. Working Draft, 14 September 2023.