Megapixel Calculator
Work out megapixels from width × height, or the pixel size from megapixels and aspect ratio, plus the largest print size at 300, 240 or 150 dpi and the raw file size.
Camera makers count megapixels in millions of pixels (10⁶). JPEG and HEIC files are typically 5–20 times smaller than the uncompressed size, depending on the picture.
| Resolution | Inches | Centimetres |
|---|---|---|
| 72 dpi | 83.33 × 55.56 in | 211.7 × 141.1 cm |
| 150 dpi | 40 × 26.67 in | 101.6 × 67.7 cm |
| 240 dpi | 25 × 16.67 in | 63.5 × 42.3 cm |
| 300 dpi | 20 × 13.33 in | 50.8 × 33.9 cm |
| 600 dpi | 10 × 6.67 in | 25.4 × 16.9 cm |
A megapixel is one million pixels. Camera and phone specs quote megapixels, but what you usually want to know is the pixel size of the photos, their shape and how large you can print them without visible pixels. Enter the width and height in pixels — or megapixels and an aspect ratio — to get all of that, plus the uncompressed size of the image in memory.
How to use this tool
- Choose whether you know the pixel size or the megapixels.
- Enter the width and height, or the megapixels and the sensor's aspect ratio.
- Set the print resolution you are aiming for (300 dpi for photo prints).
- Read the megapixels, aspect ratio, maximum print size and file size; the table compares common resolutions.
Formula
megapixels = width × height ÷ 1,000,000; print size = pixels ÷ dpi; width from megapixels = √(MP × 10⁶ × a ÷ b) for an a:b ratio
The aspect ratio is width:height divided by their greatest common divisor. The uncompressed size is width × height × 3 bytes for 8-bit RGB (24 bits per pixel); 1 MB = 10⁶ bytes and 1 MiB = 1,048,576 bytes.
Example
A 24 MP camera with a 3:2 sensor makes 6000 × 4000 px photos: √(24,000,000 × 3 ÷ 2) = 6000 and 6000 × 2 ÷ 3 = 4000. At 300 dpi they print up to 6000 ÷ 300 = 20 × 13.33 in (50.8 × 33.9 cm); uncompressed each photo is 6000 × 4000 × 3 = 72,000,000 bytes (72 MB).
Frequently asked questions
How many megapixels do I need for a print?
At 300 dpi, a 4 × 6 in print needs 1200 × 1800 px (2.2 MP), an 8 × 10 in print 2400 × 3000 px (7.2 MP) and an A4 print about 8.7 MP. Larger prints are viewed from further away, so 150–200 dpi is usually enough for posters.
Are more megapixels always better?
No. Beyond what you print or display, extra pixels mainly add file size. Sensor size, lens quality and light matter more for image quality.
Why is my 12 MP phone photo 4032 × 3024?
4032 × 3024 = 12,192,768 pixels, which is rounded to 12 MP. Makers round, and some pixels at the sensor edge are used for processing.
Last updated:
Page address with these inputs: https://kakao.mobile/tools/photo-megapixel-calculator/
Cite or embed this tool
kakaoCalc. (2026, November 8). Megapixel Calculator. https://kakao.mobile/tools/photo-megapixel-calculator/
“Megapixel Calculator.” kakaoCalc, 8 Nov. 2026, kakao.mobile/tools/photo-megapixel-calculator/.
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