Enter image dimensions, format, and quality settings to instantly estimate the file size in KB or MB - No upload required, all calculations happen in your browser.
JPG & WebP bars use quality 85. RAW = largest reference (100%).
Image Format Guide
A quick reference for choosing the right format based on transparency support, compression type, and typical use cases.
Format
Compression
Transparency
Typical Size*
Best For
JPG / JPEG
Lossy
No
200–600 KB
Photographs, social media, email
PNG
Lossless
Yes
500 KB–3 MB
Logos, icons, screenshots, graphics with text
WebP
Lossy / Lossless
Yes
150–450 KB
Web images, modern browsers, replacing JPG/PNG
AVIF
Lossy / Lossless
Yes
80–300 KB
Next-gen web images, HDR content
GIF
Lossless (256 colors)
Yes (1-bit)
100 KB–2 MB
Simple animations, small graphics
BMP
None / Minimal
Rarely
3–15 MB
Windows system images, legacy compatibility
TIFF
Lossless (LZW)
Yes
5–30 MB
Print production, professional photography archival
* Approximate sizes for a 12 MP (4000×3000) photograph at typical settings.
How File Size Is Estimated
The calculator uses established models of how each image format compresses pixel data. The starting point is always the raw bitmap size: width × height × bytes per pixel. For a standard 24-bit RGB image, that's 3 bytes per pixel - So a 1920×1080 image has a raw size of about 6 MB before any compression is applied.
From there, each format applies its own algorithm. RAW and BMP store data with little or no compression, so their estimated size stays close to the raw bitmap size. PNG uses DEFLATE lossless compression and typically achieves about 40–60% reduction on photographic content. JPG and WebP use lossy compression that is highly sensitive to the quality setting - At quality 85, JPG typically uses about 10–13% of the raw pixel data, and WebP uses about 7–9%.
Keep in mind that image content matters enormously. A smooth gradient or a solid-color sky compresses far better than a dense crowd of people or a field of grass. The calculator's estimates represent typical averages. A very simple image could be 3–5x smaller than estimated; a highly complex image could be 50–100% larger. Once you know the target format, try comparing JPG, PNG, and WebP side by side with your actual image to see real file sizes.
The memory usage figure shown is the amount of RAM required to hold the fully decoded image in memory - This is always the uncompressed bitmap size and is independent of the file format used to store or transmit the image. To verify the actual dimensions, color space, and metadata of an existing image file before running estimates, use the Image Metadata Viewer.
When to Use Which Format
Web Photos
Product images, hero images, blog photos - Anywhere the image has no transparent areas and loading speed matters.
Use: WebP (preferred) or JPG q75–85
Icons & Logos
Any graphic with a transparent background, sharp edges, or solid colors where compression artifacts would be visible.
Use: PNG 24-bit or SVG (for vectors)
Screenshots
UI captures, documentation screenshots, and screen recordings where text sharpness is critical and artifacts are unacceptable.
Use: PNG 24-bit
Print & Archival
High-resolution images for printing, professional photo archives, or anything that needs to retain full quality for future editing. Use the DPI / PPI Calculator to confirm your pixel count will produce the target print size at the right resolution.
Use: TIFF or PNG 24-bit
Frequently Asked Questions
How accurate is the image file size estimate?
The estimates are based on typical real-world compression ratios for photographic content. Actual file sizes can vary by 20–40% depending on image complexity. A simple solid-color image compresses much more aggressively than a detailed photograph, even at the same dimensions and quality setting. Use the calculator as a planning tool rather than a precise prediction.
Why is PNG larger than JPG for the same image?
PNG uses lossless compression - It preserves every single pixel perfectly and then compresses the data mathematically without discarding any information. JPG uses lossy compression that discards subtle detail the eye may not notice, achieving much higher compression ratios. For a typical photo, a JPG at quality 85 is usually 3–5x smaller than an equivalent PNG, at the cost of minor compression artifacts.
Why is WebP smaller than JPG at the same quality?
WebP uses a more modern compression algorithm derived from the VP8 video codec. It is more efficient than JPEG's older DCT-based approach, particularly in how it handles smooth gradients and edge detail. At the same perceptual quality, WebP typically produces files 25–35% smaller than JPG. WebP also supports both lossless compression and transparency, making it a more flexible replacement for both JPG and PNG on the web. You can convert any JPG to WebP using our JPG to WebP converter.
How many megapixels fit in 1 MB as a JPG?
At quality 85, a typical photographic JPG uses about 0.35–0.40 bytes per pixel. That means 1 MB (1,048,576 bytes) holds roughly 2.6–3 megapixels. A 12 MP photo (4000×3000) at quality 85 will be approximately 4–5 MB for a typical outdoor photograph. Simpler images (clear sky, solid backgrounds) will be smaller; highly detailed scenes may be larger.
What is the difference between RAW and uncompressed BMP?
In this calculator, "RAW" refers to the theoretical uncompressed pixel data (width × height × 3 bytes for 24-bit color), representing the absolute maximum file size. BMP is a Windows bitmap format that is stored similarly but includes a file header and may have row padding. Camera RAW files (.CR2, .NEF, .ARW, etc.) are different - They store the raw sensor data before processing, often with their own proprietary compression, and are typically 20–30 MB for a 24 MP camera.
What does "memory usage" mean in the results?
The memory usage figure is the amount of RAM required to hold the fully decoded image as a pixel buffer - This is always the uncompressed bitmap size, regardless of how the image is stored on disk. An 8 MB TIFF and a 500 KB JPG of the same 12 MP photo will both require approximately 36 MB of RAM when decoded for display or editing. This is important to keep in mind when working with large images or multiple images simultaneously.
Does image content affect file size?
Yes - Significantly. Image content is one of the biggest factors in real-world file size. Smooth gradients, simple backgrounds, and low-detail images compress very efficiently in all formats. Complex textures, film grain, foliage, crowds, and detailed patterns compress much less. A photograph of an empty beach and a photograph of a forest at the same dimensions and JPG quality setting may differ in file size by 2–4x. The calculator uses average values representative of typical photographic content. To actually reduce file size, use our JPG compressor to find the optimal quality/size balance for your specific image.
