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Megapixel Calculator: Resolution, MP and Print Size

This free calculator turns an image size in pixels into megapixels, or works out the width and height for a megapixel count and aspect ratio, and shows the largest prints you can make at common DPI values.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is It and When Do You Need It?

Camera and phone makers sell by megapixels. To compare them, or to check if an image is big enough for a print, you need the actual pixel size.

Choose a mode and enter the numbers.

How to Use This Tool

  1. Enter or paste your input in the box or boxes above.
  2. Choose the options, if there are any.
  3. Press the button to run the tool.
  4. Read the result and use the copy button where one is shown.

How the Calculation Works

Megapixels equal width times height divided by one million. In the reverse mode the total pixels are the megapixels times one million, and the width is the square root of pixels times aspect width over aspect height. The print table divides the width and height by the DPI values 100, 150, 200 and 300.

Worked Example

4000 x 3000 is 12 MP. 24 MP at a 3:2 ratio is about 6000 x 4000 pixels.

Common Uses

  • Comparing cameras.
  • Checking if a photo is big enough.
  • Web image sizing.
  • Print planning.

Tips and Common Mistakes

  • Crop reduces the pixel count.
  • Phones may use pixel binning to give fewer, better pixels.
  • For screens use the DPI and PPI calculator.
  • Check the first result against a case you already know, so you can trust the tool for the rest.
  • Nothing you type leaves your device. The work is done by your browser, so it also works with a slow connection once the page has loaded.

Next, you may need the DPI and PPI calculator, aspect ratio calculator, JSON formatter and validator, CSV and JSON converter.

Everything runs in your browser. Nothing you type is uploaded, stored or sent to any outside service.

Frequently Asked Questions

One million pixels. A 4000 x 3000 image has 12,000,000 pixels, so it is 12 megapixels.
Only up to a point. Sensor size, lens and light matter more once you have enough pixels for your use.
For an 8 x 10 inch print at 300 DPI you need 2400 x 3000 pixels, which is about 7.2 megapixels.
Width = the square root of (pixels x aspect width / aspect height), and the height follows from the aspect ratio.

Disclaimer: results are calculated in your browser from the numbers you enter. Check important results before you rely on them for money, health, safety or legal decisions.