What the image file size calculator does
Enter an image's width and height in pixels and its colour depth, and the calculator returns the uncompressed size — the amount of memory the image occupies when decoded, and the size of a raw or uncompressed file such as a BMP or an uncompressed TIFF. It is the number behind storage planning for scans and screenshots, memory budgets in apps and games, video frame sizes, and understanding why a 24-megapixel photo is 72 MB in memory but 8 MB as a JPG. Runs in your browser.
The formula
Size (bytes) = width × height × bits per pixel ÷ 8
1920 × 1080 at 24-bit: 1920 × 1080 × 3 = 6,220,800 bytes = 5.9 MiB (6.2 MB)
4000 × 3000 at 24-bit: 36,000,000 bytes = 34.3 MiB
4000 × 3000 at 32-bit (RGBA): 48,000,000 bytes = 45.8 MiB
1920 × 1080 at 8-bit greyscale: 2,073,600 bytes = 2.0 MiBThe calculator reports both decimal (MB, 1,000,000 bytes) and binary (MiB, 1,048,576 bytes) units, since file managers and camera specs use them inconsistently.
Colour depths
| Depth | Bytes per pixel | Colours | Where used |
|---|---|---|---|
| 8-bit greyscale | 1 | 256 greys | Scans of text, medical and scientific imaging |
| 16-bit | 2 | 65,536 (RGB565) or 16-bit grey | Embedded displays, some scanners |
| 24-bit RGB | 3 | 16.7 million | Standard photos, screenshots, JPG |
| 32-bit RGBA | 4 | 16.7 million + 256 alpha levels | PNG with transparency, textures, UI, in-memory images |
| 48-bit RGB (16 per channel) | 6 | 281 trillion | RAW conversions, HDR, print-grade TIFF |
Uncompressed vs actual file size
| Format | Typical size vs uncompressed | Why |
|---|---|---|
| BMP, uncompressed TIFF, raw | 100% | Stores every pixel |
| PNG (photo) | 50–80% | Lossless; photos compress poorly |
| PNG (screenshot, graphic) | 5–30% | Flat colour compresses well |
| JPG at 90% | 8–15% | Lossy; discards invisible detail |
| JPG at 75% | 4–8% | |
| WebP lossy | 3–6% | |
| Camera RAW | 40–70% | 12–14-bit sensor data, lightly compressed |
A 4000 × 3000 photo is 34 MiB decoded but 3–5 MB as a JPG; the calculator gives the first number. The Image Compressor and converters deal with the second.
Common uses
- Memory budgets: an app holding twenty 12-megapixel images decoded needs 720 MiB of RAM at 24-bit — a common cause of mobile crashes.
- GPU textures: a 4096 × 4096 RGBA texture is 64 MiB before mipmaps (add a third); compressed formats (BC7, ASTC) cut this by 4–8×.
- Scanning projects: 1,000 pages at 300 dpi A4 (2480 × 3508) in 24-bit is 26 GB uncompressed, about 300 MB as greyscale JPG.
- Video: uncompressed 1080p at 24-bit is 6.2 MB per frame, 187 MB/s at 30 fps — which is why capture and editing use compressed intermediates.
- Bandwidth and storage planning for camera systems, archives and medical imaging.