Megapixel
A megapixel is a million pixels, the unit for an image’s total pixel count, found by multiplying its width by its height.
What it means
Multiply an image’s width by its height in pixels and you have its total pixel count. Divide that by a million and you have megapixels. A picture 2000 by 1500 holds 3,000,000 pixels, which is 3 megapixels.
Channels use megapixels for their upper limits. Google takes product images of up to 64 megapixels.1 Shopify’s ceiling is lower: images of “any size up to 5000 x 5000 px, or 25 megapixels”.2
A camera’s megapixel figure is the most it can capture, not what reaches your store. A picture saved from a supplier’s website may hold a small fraction of it, so measure the file you actually have.
Think of it like this
Megapixels are to pixels what kilometres are to metres: the same thing counted in a bigger unit, so that very large numbers stay readable.
For example
A manufacturer’s original is 6000 by 6000 pixels, which is 36 megapixels. That is within Google’s 64 but over Shopify’s 25, so it is resized for the store. At 5000 by 5000 it is exactly 25 megapixels, within both limits.
Why it matters
Upper limits catch the best images, not the worst. The full-size originals worth hunting for can be bigger than a store will take. Shopify’s advice for an image over its limit is to “Reduce the size of the image or use a different image”.3
Not to be confused with
A megapixel is a different thing from a megabyte. Megapixels count pixels; megabytes (MB) measure the file on disk. Google sets a limit on each, 64 megapixels and 16 MB,1 and an image can pass one and fail the other.
Sources
- Google Merchant Center Help. Image link [image_link].
- Shopify Help Center. Product media types.
- Shopify Help Center. Solutions to common product CSV import problems.