Image Size Calculator

What this tool does

Image Size Calculator estimates file sizes for images based on pixel dimensions and color depth before you create them. When planning photography storage, designing graphics, or preparing for batch processing, knowing expected file sizes helps with capacity planning, upload time estimates, and format selection. The calculator compares multiple formats simultaneously so you can choose the optimal one for your needs.

Rather than creating test images in each format, the calculator uses mathematical formulas that model compression behavior. Results are estimates since actual compression efficiency varies with image content, but they're accurate enough for planning purposes.

How to use this tool

1. Enter the image width and height in pixels.

2. Select the color depth (bit depth) representing how many colors your image uses.

3. View calculated file sizes for multiple formats: BMP, TIFF, PNG, JPEG (multiple quality levels), WebP, and GIF.

4. Compare formats to choose the best balance of quality and size for your needs.

5. Use presets for common resolutions (HD, 4K, social media sizes) for quick calculations.

Common use cases

• Estimate storage requirements before a photo shoot
• Plan server capacity for image hosting platforms
• Compare format efficiency for batch processing decisions
• Calculate upload times based on connection speed and estimated file sizes
• Verify image dimensions meet minimum requirements while predicting output size
• Plan email attachments to stay under size limits
• Estimate cloud storage costs based on image volume
• Choose optimal format before designing graphics

Key features and behavior

Color depth options

Select the bit depth matching your image type: 1-bit for monochrome (black and white only), 8-bit for grayscale (256 shades), 24-bit for standard color (16.7 million colors), or 32-bit for color with transparency (alpha channel). Higher bit depths produce larger raw files but may compress differently.

Format comparisons

The calculator shows sizes for BMP (uncompressed reference), TIFF (minimal compression), PNG (lossless compression), JPEG at multiple quality levels (lossy compression), WebP (modern efficient format), and GIF (limited colors). This side-by-side comparison reveals dramatic differences in format efficiency.

Compression modeling

Estimates use typical compression ratios: JPEG at 80% quality averages about 8-10% of raw size for photographs; PNG varies widely based on content complexity (20-60% of raw); WebP achieves 30% smaller than equivalent JPEG. Actual results vary based on image content—complex textures compress less than solid colors.

Quick presets

Standard dimension presets include: HD (1280×720), Full HD (1920×1080), 4K (3840×2160), 8K (7680×4320), plus social media dimensions (Instagram, Facebook, Twitter headers/thumbnails). These accelerate calculations for common use cases.

Tips and limitations

• Estimates assume typical photographic content; graphics with solid colors compress better
• JPEG quality settings affect size dramatically—quality 50 is roughly half the size of quality 80
• PNG size depends heavily on content; simple graphics compress much better than photos
• GIF estimates assume 256 colors maximum; converting photos to GIF causes quality loss
• RAW camera files aren't estimated as their structure varies by camera manufacturer
• Metadata (EXIF) adds a few KB not included in these calculations

FAQ

Why are estimates different from actual file sizes?

Compression efficiency depends on image content. Photos with fine detail and texture compress less than images with solid colors or gradients. Estimates use average compression ratios; your actual results may be 20-50% different based on content.

What color depth should I choose?

For standard photographs: 24-bit (True Color). For images with transparency: 32-bit. For grayscale photos: 8-bit. For simple black-and-white graphics: 1-bit. Higher depths support more colors but increase file size.

Why is PNG sometimes larger than JPEG for photos?

PNG uses lossless compression which preserves every pixel exactly. For complex photographs with millions of subtle color variations, this results in larger files than JPEG's lossy compression. PNG excels for graphics, not photographs.

What's the smallest format for photographs?

WebP typically achieves the smallest file sizes for photographs while maintaining good quality. JPEG at lower quality settings (60-70) can be smaller but with visible artifacts. For maximum compression, WebP lossy is usually optimal.

How accurate are these estimates?

Estimates are within ±30% for typical photographic content. Graphics with large solid color areas compress better than estimated; noisy or highly detailed images compress worse. Use estimates for planning, not exact calculations.

Can I calculate video file sizes?

No, this tool is for still images only. Video file sizes depend on codec, bitrate, framerate, and duration—different variables requiring different calculations.

Why does BMP show such large file sizes?

BMP is essentially uncompressed, storing raw pixel data directly. It represents the theoretical maximum size for a given dimension and color depth, serving as a baseline to show how much compression other formats achieve.

What format should I use for web images?

WebP offers the best size-to-quality ratio for modern browsers. Use JPEG as a fallback for older browsers. PNG is necessary only when you need transparency or pixel-perfect graphics. Avoid BMP and uncompressed TIFF for web use.