Design video thumbnails at 1280×720 minimum
YouTube recommends 1280×720 as the minimum thumbnail size (16:9). Upload at 1920×1080 for the sharpest display on high-DPI screens — YouTube compresses it down but you want to start with maximum quality. The aspect ratio calculator makes it easy to check: enter ratio 16:9 and width 1280 to confirm height 720, or 1920 for height 1080.
The CSS aspect-ratio property
Modern CSS lets you maintain any aspect ratio with a single line: aspect-ratio: 16 / 9. Combine with width: 100% and the element maintains its ratio at any container width. This replaces the old padding-bottom hack. For older browser support (pre-2021), the padding-bottom percentage is: (height ÷ width) × 100. The calculator gives you both the ratio and the multiplied dimensions to verify.
Social media image sizes cheat sheet
LinkedIn post: 1200×627 (1.91:1). Twitter/X card: 1200×675 (16:9). Instagram square: 1080×1080 (1:1). Instagram portrait: 1080×1350 (4:5). Instagram landscape: 1080×566 (≈1.91:1). Instagram Story/TikTok: 1080×1920 (9:16). Facebook event cover: 1920×1005 (≈1.91:1). Pinterest pin: 1000×1500 (2:3). Use the calculator to verify any of these and find scaled-down versions for production.
Photography print ratios
Most digital cameras shoot at 3:2 (full-frame DSLRs). Standard print sizes do not always match 3:2: 4×6 is 3:2 (perfect match), 5×7 is 7:5 (crops slightly), 8×10 is 5:4 (crops significantly), A4 paper is approximately 1.414:1 (ISO 216 standard). When printing, always enter your print dimensions and your photo dimensions to see how much will be cropped at each size.
The megapixel column as a file size guide
The megapixel (MP) count in the common sizes table correlates directly to uncompressed image file size. A 2MP image at 24 bits per pixel is approximately 6MB uncompressed (6 = 2 × 3). After JPEG compression at 80% quality, expect roughly 1–2MB. At 20MP, that is 10–20MB compressed. This is useful for estimating storage requirements when planning a photo library or video production pipeline.