Image File Size Calculator
Estimate the uncompressed size of an image from its dimensions and bit depth, with a rough JPEG figure too.
How it works
Every pixel in an uncompressed image needs a fixed number of bits. Multiply the width by the height to get the pixel count, multiply that by the bit depth, and divide by eight to turn bits into bytes.
Bit depth depends on the format: 8-bit grayscale, 24-bit RGB colour (the common one), or 32-bit RGBA with an alpha channel. A 1920×1080 image at 24-bit is about 6.2 MB raw — which is why nobody ships bitmaps.
JPEG and other formats compress hard, often 8:1 to 30:1 depending on quality and how busy the picture is. The rough JPEG estimate here applies a typical ratio, but the real size always depends on the specific image.
Frequently asked questions
Why is the uncompressed size so much bigger than my JPEG?
JPEG throws away detail your eye barely notices and packs the rest tightly, often shrinking a file ten- or twenty-fold. The uncompressed figure is what the raw pixel grid would weigh with no compression at all.
What bit depth should I pick?
Use 24-bit for normal full-colour photos and graphics. Choose 32-bit when you need transparency (an alpha channel), and 8-bit for simple grayscale or paletted images.
How accurate is the JPEG estimate?
It's a ballpark. A flat, simple image compresses much smaller than a detailed, noisy one at the same quality setting, so use the estimate for planning and check the actual export for the real number.