Image File Size Calculator
Estimate image file sizes for JPEG, PNG, WebP, TIFF, BMP and GIF. Compare compression formats side by side with quality controls. Plan storage and bandwidth.
Quick Presets
Image Dimensions
Color Depth
Selected Format
Compressed Formats
JPEG
Lossy compression
PNG
Lossless compression
WebP
Modern, highly efficient
TIFF
Professional, uncompressed
BMP
Uncompressed bitmap
GIF
Lossless, limited colors
Quick Comparison
| Format | Size | Compression | Best For |
|---|---|---|---|
| JPEG | 1.97 MB | 3.01:1 | Photos |
| PNG | 2.97 MB | 2.00:1 | Graphics |
| WebP | 1016.57 KB | 5.98:1 | Web |
| TIFF | 6.53 MB | 0.91:1 |
What Determines Image File Size
Three main factors: dimensions (width × height in pixels), bit depth (colour information per pixel - typically 8-bit RGB = 24 bits per pixel), and compression. A raw uncompressed 1920×1080 image = 6.2 MB (1920 × 1080 × 3 bytes). Same image as JPEG at 80% quality: 200-400 KB. Same as WebP: 150-250 KB. Same as PNG: 1-3 MB (lossless).
Compression ratios vary hugely by image content. Photos (lots of complex detail) compress less efficiently - JPEG might achieve 10-20x compression. Simple graphics with flat colours compress better - 50-100x compression in PNG-8 or JPEG. Animation (GIF or animated WebP) multiplies size by frame count. Plan for typical 5-15x compression in JPEG and 8-15x in WebP for photos.
Common File Sizes by Use Case
Web hero image (1920×1080): 100-300 KB JPEG, 80-200 KB WebP. Email signature: 5-20 KB optimised. Social media post (1080×1080): 100-200 KB. Logo (transparent PNG): 50-200 KB depending on complexity. Product photography (high quality): 500 KB - 2 MB. Print-quality photo (300 DPI for A4): 5-15 MB raw or PNG; 1-3 MB JPEG.
Mobile considerations: keep web images under 200 KB total. Lazy-loading helps with image-heavy pages but doesn't help on first paint. Modern formats (WebP, AVIF) save 25-50% over JPEG with similar quality - use them where browser support exists. Always provide fallback for older browsers via the picture element.
Reducing File Sizes
Quality reduction: drop JPEG quality from 100% to 75-85% - typically saves 50-70% file size with minimal visible quality loss. Resize to actual display dimensions: don't serve 4K images for 800px display. Format conversion: PNG to JPEG for photos (WebP if supported); GIF to MP4/WebP for animations. Tools: TinyPNG/TinyJPG (free, browser-based), Squoosh.app (Google, advanced), ImageOptim (Mac), Squoosh CLI for batch processing.
Aspect ratio choice: square (1:1) ideal for product/profile. 16:9 for hero/video. 4:3 for traditional portrait. Avoid arbitrary aspect ratios - hard to fit responsive layouts. Modern responsive images (srcset attribute) serve different sizes to different devices, dramatically reducing data for mobile. Use the [Screen PPI Calculator](/screen-ppi-calculator) for understanding device pixel densities.
Format Comparison
JPEG: lossy, great for photos, no transparency, universal support. WebP: lossy or lossless, smaller than JPEG, supports transparency, all modern browsers (90%+ market share). AVIF: even smaller than WebP, newer (2020+), 70%+ browser support. PNG: lossless, supports transparency, larger than JPEG/WebP. SVG: vector, infinitely scalable, perfect for logos/icons. GIF: animated, limited colours, replaced by MP4/WebP for modern uses.
Recommendation by use: photos = JPEG (compatibility) or WebP (size). Logos/icons = SVG or PNG. Detailed graphics = PNG. Animation = MP4 or WebP. Modern web standards: serve WebP/AVIF where supported with PNG/JPEG fallback. Modern frameworks (Next.js, Astro, Nuxt) handle format selection automatically based on browser capabilities.
Frequently Asked Questions
What's a good file size for web?
Under 200 KB per image typically; under 100 KB ideal for above-the-fold images on pages. Lazy-loading lets below-the-fold images be larger (300-500 KB) without affecting initial page load. Mobile-first: prioritise small images for slow connections.
How do I reduce JPEG without losing quality?
Quality 80-85% retains visual quality with major file size reduction. Below 75% becomes visibly degraded. Use mozjpeg or jpeg-archive for advanced encoding (smaller files at same quality). Most online tools (TinyJPG, Squoosh) achieve excellent compression for free.
Is WebP universally supported now?
90%+ browser support including all modern Chrome, Firefox, Edge, Safari. Older Safari (iOS <14) and IE11 don't support WebP - use picture element with fallback. AVIF has growing support (~75%) but requires more careful fallback strategy.
Should I use PNG or JPEG?
Photos: JPEG (smaller). Graphics/text/transparency needed: PNG. Logos: SVG (best). Decision: complex multi-colour photos = JPEG. Anything with transparency, sharp edges, simple colour = PNG. Modern alternative: WebP supports both lossy and lossless modes.
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