How is image file size estimated?

It multiplies the image's pixel dimensions (width x height) by color depth, then applies an estimated compression factor depending on format (JPEG, PNG, etc.).

Why do JPEG and PNG files differ so much in size for the same image?

JPEG uses lossy compression optimized for photos, producing smaller files; PNG uses lossless compression, better for graphics with sharp edges but often larger for photos.

Does image content affect file size at the same resolution?

Yes — busier images with more detail and color variation typically compress less efficiently than simpler images, resulting in larger file sizes.

Image File Size Estimator - CalculatorLabs.net

Image File Size Estimator

Estimate an image's uncompressed and compressed file size from its resolution.

Width (pixels)

Height (pixels)

Color Depth

JPEG Compression Level

Uncompressed (Raw) Size -

Estimated Compressed (JPEG) Size -

What Is the Image File Size Estimator?

The Image File Size Estimator calculates the theoretical uncompressed size of an image based on its resolution and color depth, then estimates a realistic compressed JPEG file size using a typical compression ratio.

Formula Used

Raw Size (bytes) = Width × Height × (Bit Depth ÷ 8)
Compressed Size ≈ Raw Size ÷ Compression Ratio

Actual compressed file size varies with image content (photos compress differently than flat graphics) — this gives a useful ballpark estimate for planning storage or bandwidth needs.

How to Use This Calculator

Enter the image width and height in pixels.
Select the color depth (24-bit true color is standard for photos).
Select an approximate JPEG compression/quality level.
Click Calculate to see the raw and estimated compressed sizes.

Worked Example

A 1920×1080 24-bit image has a raw size of 1920×1080×3 = 6,220,800 bytes (≈5.93 MB). At medium JPEG compression (~10:1), the estimated compressed size is about 0.59 MB.