Enter an image's width and height to see how large it is uncompressed and roughly how large it will be as a JPEG, WebP, AVIF, PNG, GIF, or TIFF. Or drop an actual image: the calculator encodes it in your browser in each format at several quality levels and shows the real file sizes, so you can see which format and quality gives the smallest file and download it. Need a file under a size limit, such as 500 KB for an upload form? Enter the limit and it finds the highest quality that fits. Nothing is uploaded.
How to calculate image file size
An uncompressed image takes up its pixel count multiplied by the bits stored for each pixel:
file size in bytes = width × height × bit depth ÷ 8
A 4032 x 3024 photo from a 12-megapixel phone has 12,192,768 pixels. At 24-bit color (8 bits each for red, green, and blue), that's 12,192,768 × 24 ÷ 8 = 36,578,304 bytes, or about 36.6 MB. That's the size of a BMP file, and roughly the memory a browser or app needs to display the image. Compression is why the same photo is usually a 2 to 4 MB JPEG.
Uncompressed size of common image dimensions
| Dimensions | Megapixels | 8-bit gray | 24-bit RGB | 32-bit RGBA |
|---|---|---|---|---|
| 1080 x 1080 | 1.2 | 1.17 MB | 3.5 MB | 4.67 MB |
| 1920 x 1080 (1080p) | 2.1 | 2.07 MB | 6.22 MB | 8.29 MB |
| 2480 x 3508 (A4 at 300 DPI) | 8.7 | 8.7 MB | 26.1 MB | 34.8 MB |
| 3840 x 2160 (4K) | 8.3 | 8.29 MB | 24.9 MB | 33.2 MB |
| 4032 x 3024 (12 MP phone) | 12.2 | 12.2 MB | 36.6 MB | 48.8 MB |
| 6000 x 4000 (24 MP camera) | 24 | 24 MB | 72 MB | 96 MB |
Sizes use 1 MB = 1,000,000 bytes. Windows File Explorer divides by 1,048,576 instead, so it shows the same file about 5% smaller. The calculator shows both.
How much each format compresses
Compressed size depends on what's in the image, not just its dimensions. Smooth areas like sky compress well, while fine detail, film grain, and noise don't. The calculator's estimates use typical bits per pixel for each format, and the measured sizes for your own image are exact.
| Format | Typical photo | Best for |
|---|---|---|
| JPEG | 1 to 3 bits per pixel, about 10:1 compression | Photos where small files matter and transparency isn't needed |
| WebP | About 25 to 35% smaller than JPEG at similar quality | Websites. Supports transparency and lossless mode |
| AVIF | About 50% smaller than JPEG | Websites where every kilobyte counts. Slower to encode |
| PNG | 10 to 16 bits per pixel for photos, far less for graphics | Screenshots, logos, text, and anything needing exact pixels |
| GIF | Limited to 256 colors | Simple animations. Use PNG or WebP for still images |
| BMP | No compression: exactly the uncompressed size | Legacy software only |
How to make an image file smaller
Reduce the dimensions. File size scales with pixel count, so halving the width and height cuts the file to about a quarter. A photo for a website rarely needs to be wider than 1920 to 2560 pixels. Use the Output size menu to see the effect before you download.
Choose the right format. Photos are usually smallest as AVIF or WebP. Screenshots and graphics with flat colors are often smaller as PNG or lossless WebP than as JPEG, and they look sharper too.
Lower the quality a little. Going from 95% to 85% JPEG quality often halves the file with no visible difference. Below about 60%, blockiness and smeared edges start to show.
Frequently asked questions
How do I calculate the file size of an image?
Multiply the width by the height to get the pixel count, multiply by the bit depth (24 for normal color, 32 with transparency), and divide by 8 to get bytes. Divide by 1,000,000 for megabytes. This is the uncompressed size. Compressed formats like JPEG are usually 5 to 20 times smaller.
How big is a 1920 x 1080 image?
Uncompressed at 24-bit color it is 6,220,800 bytes, about 6.2 MB. As a JPEG it is typically 300 KB to 800 KB for a photo, and as a PNG screenshot often 100 KB to 1 MB depending on the content.
How can I get an image under 100 KB or 500 KB?
Drop the image, enter the limit in the Fit under box, and choose JPEG or WebP. The calculator searches for the highest quality that fits. If that would mean going below 40% quality, where JPEG artifacts become obvious, it reduces the dimensions instead. Then download the result.
Why is my PNG bigger than my JPEG?
PNG is lossless, so it keeps every pixel exactly, including the fine noise in photos that JPEG throws away. For photos, PNG is often five or more times larger. For screenshots and logos with flat colors, PNG can be smaller than JPEG and looks sharper.
Does DPI change the file size?
No. DPI is only a label for print size. A 3000 x 2000 image has the same number of pixels and the same file size whether it is tagged 72 or 300 DPI.
Are my images uploaded?
No. Images are decoded and encoded by your own browser, and nothing is sent to a server. The sizes shown are from your browser's encoders, which can differ slightly from Photoshop or other apps.