Image Size Calculator
Enter width × height in pixels and bit depth to calculate the uncompressed file size. Estimated JPG/PNG sizes are also displayed.
Results are provided for reference only and may differ from actual values.
Understanding Image File Sizes
How file size is calculated
An uncompressed image file size is simply width × height × bit depth ÷ 8 bytes. A 1920×1080 RGB image (24-bit) takes 1920 × 1080 × 24 ÷ 8 = 6,220,800 bytes ≈ 5.93 MB before compression. But nobody stores uncompressed files — that's why we have JPG, PNG, and WebP.
Compression ratios — JPG vs PNG vs WebP
- JPG (quality 80): 8–15% of uncompressed. Our 5.93 MB image becomes ~600 KB
- JPG (quality 95): 15–25% of uncompressed (~1.2 MB)
- PNG (lossless): 40–70% of uncompressed (~3 MB) — higher for photos, lower for flat graphics
- WebP (quality 80): 5–10% of uncompressed (~400 KB) — best modern format
- AVIF (quality 80): 3–7% of uncompressed (~250 KB) — newest, supported by most browsers
Bit depth and color accuracy
- 8-bit grayscale (1 channel): 256 shades of gray. Used in B/W line art.
- 24-bit RGB (3 channels × 8-bit): 16.7 million colors. Standard for photos, web, JPG.
- 32-bit RGBA: 24-bit RGB + 8-bit alpha channel for transparency. Used in PNG with transparency.
- 48-bit RGB (16-bit per channel): Professional photography / HDR. Photoshop .psd, some RAW formats.
When you hit upload limits
Common upload limits and what they mean:
- Gmail attachment: 25 MB per email — 4–5 phone photos before it refuses
- WhatsApp / KakaoTalk: 16 MB (WA) / 30 MB (KT) — compresses photos automatically
- GitHub file: 100 MB limit, 50 MB warning
- Discord free: 25 MB per file
- WordPress default: 2 MB (can be increased via server config)
- Instagram upload: internal compression aggressive; export at 1080 wide for best preservation
Tips for shrinking file size without losing quality
- Resize before compressing — a 6000×4000 photo resized to 2000×1333 already shrinks to ~11% of original.
- Use JPG quality 80 for most photos — visually identical to 100%, file is half the size.
- Convert to WebP where supported (all modern browsers since 2020).
- Strip EXIF metadata if you don't need GPS/camera info — saves 10–200 KB per photo.
- For screenshots and line art, PNG-8 (256 colors) is often sufficient and much smaller than PNG-24.
Frequently Asked Questions
Q. How is uncompressed image size calculated?
Width (px) × Height (px) × (Bit Depth ÷ 8) = uncompressed file size in bytes.
Q. Why are JPG and PNG estimated sizes different?
JPG uses lossy compression, typically resulting in 10–20% of the uncompressed size. PNG uses lossless compression, resulting in about 50–70% of the uncompressed size.
Q. What is bit depth?
Bit depth is the number of bits used to represent each pixel. 8-bit grayscale = 256 shades; 24-bit RGB = 16.77 million colors; 32-bit RGBA adds transparency. Higher bit depths (48-bit+) are used in professional HDR workflows.
Q. How do I calculate image file size for a print?
Multiply print dimensions by DPI first: a 4×6 inch print at 300 DPI = 1200×1800 pixels. Then 1200 × 1800 × 3 bytes = 6.18 MB uncompressed; JPG quality 90 ≈ 1 MB.
Q. Does file size include metadata (EXIF)?
Real file size includes pixel data, EXIF metadata (camera settings, GPS), ICC color profiles, and thumbnails — adding 10–200 KB. Strip with ImageOptim or exiftool for smaller uploads.
Q. Why is my saved JPG smaller than this estimate?
Photos with large flat areas (blue sky, solid backgrounds) compress to 3–5% of uncompressed. Complex textures compress less. Smartphones use HEIC/HEIF with even better compression than JPG.
Related Tools
Results are provided for reference only and may differ from actual values. This tool is for informational purposes and should not be used as a basis for legal, financial, or medical decisions.