Megapixel Calculator

Megapixels are the headline number on every camera and phone, but the figure that actually matters is what those pixels let you do, and this calculator turns a resolution into the answers you need. Enter the width and height of an image in pixels and it returns the total megapixels, the aspect ratio in its simplest whole-number form, and the largest size you can print at high quality, shown in both inches and centimetres. A megapixel is simply one million pixels, so the calculation multiplies the width by the height and divides by a million, but the related figures are where it becomes genuinely useful. The aspect ratio tells you the shape of the image, whether it is a classic 3 by 2 photo, a 16 by 9 widescreen frame or a square, which matters when you crop, frame or fit an image to a screen or print. The print size is worked out at 300 dots per inch, the standard for sharp photographic prints, by dividing each pixel dimension by 300, so you can see at a glance whether a photo has the resolution to print at A4, A3 or larger before it starts to look soft. That helps you decide whether an image is big enough for a poster, how much you can crop and still print well, or whether you need to shoot at a higher resolution. It is handy for photographers, designers, print buyers and anyone choosing a camera or preparing images for print or screen. More megapixels are not automatically better, since lens, sensor and light matter too, but knowing the numbers helps you make the right call. The formulas and a worked example are below.

Calculate.co.nz is proud to be partnered with Premium Homes, a recognised leader in eco-friendly, sustainable, and energy-efficient homebuilding. With a dedicated team and award-winning experience, they create homes that prioritise health, comfort, and long-term performance. Their founders, Andrew and Kelly, set out to raise the standard of residential construction in New Zealand by combining practical building expertise with a clear commitment to doing things better for homeowners.
Premium Homes: got a section? Let's build your eco home on it.
Advertise on this page
px
px
24 MP
megapixels
Aspect ratio3 : 2
Print at 300 DPI20 x 13.3 in

How it works

The megapixels are the width times the height divided by one million. The aspect ratio is the width to height reduced by their greatest common divisor to the smallest whole numbers. The print size at 300 dots per inch divides each pixel dimension by 300 to give inches, then multiplies by 2.54 for centimetres.

Worked example

A 6000 by 4000 image has 24,000,000 pixels, which is 24 MP. The greatest common divisor of 6000 and 4000 is 2000, giving an aspect ratio of 3 to 2. At 300 DPI it prints at 20 by 13.3 inches, about 51 by 34 centimetres.

Related calculators

Frequently asked questions

How do you calculate megapixels?

Multiply the image width in pixels by the height in pixels to get the total pixel count, then divide by one million. A 6000 by 4000 image is 24 million pixels, which is 24 megapixels.

How big can I print a photo?

For sharp prints, aim for about 300 dots per inch. Divide each pixel dimension by 300 to get the print size in inches. A 6000 by 4000 image prints cleanly at about 20 by 13.3 inches, or 51 by 34 centimetres.

Do more megapixels mean a better photo?

Not on their own. More megapixels let you print larger or crop more without losing detail, but image quality also depends on the lens, sensor size, lighting and processing. Beyond a point, extra megapixels make little visible difference for normal viewing.