Aspect ratio calculator
Fix aspect W:H, then enter width or height — we compute the other side.
Keeping proportions intact
Aspect ratio calculations help when you know one dimension and need the other without stretching the image or frame. That matters for video thumbnails, presentation slides, banners, and cropped photos where the shape must stay consistent.
Useful presets and custom ratios
Common ratios like 16:9, 4:3, and 1:1 cover most video and social formats, but custom ratios are better for unusual layouts. Enter the dimensions you already have, then use the calculator to scale up or down while preserving the original look.
Video and social presets
Sixteen-by-nine fits YouTube and most HD video. Four-by-three suits legacy slides. Instagram squares use one-to-one — enter custom ratios for Stories or Pinterest pins.
Math
Maintain proportion when scaling video or image frames — rounding matters for crisp pixels.
Crop planning
When you crop a photo for Instagram or YouTube thumbnails, knowing the target ratio first avoids cutting off faces or product labels. Enter the final frame size, then resize source material to match rather than guessing in an editor.
Quick start
- Enter known dimensions — Provide width and height, or width and ratio, depending on what you know.
- Choose a preset or custom ratio — Use 16:9, 4:3, or enter a custom aspect for video and image frames.
- Read scaled dimensions — Copy pixel values that preserve proportion for export or crop planning.