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Aspect Ratio & Crop Calculator
Enter a source width and height (or pick a preset) and a target aspect ratio to get exact crop dimensions and offset, plus the padded letterbox/pillarbox dimensions if you'd rather keep the full frame.
Crop vs. letterbox/pillarbox
Converting between aspect ratios means picking one of two trade-offs: crop-to-fit fills the entire target frame with sharp, undistorted pixels but throws away whatever falls outside the crop box. Letterbox or pillarbox padding keeps every pixel of the original shot but adds black (or blurred/colored) bars to reach the target ratio. This tool calculates the exact numbers for both approaches from the same source and target dimensions.
What this can't do
It computes geometry only — it doesn't know what's actually in your frame. A centered subject crops cleanly to 9:16; a subject near the left edge of a 16:9 shot might get cut off entirely by an automatic center-crop. Always check the crop box against your actual footage before exporting.
Frequently asked questions
How is the crop always centered?
This tool assumes a center crop, which is the standard default when you don't have a specific subject to track. It scales the crop box to the target aspect ratio using the source's shorter dimension for that axis, then centers the offset evenly on both sides.
Which should I use for Instagram Reels or TikTok — crop or pad?
Crop is almost always the better call for 9:16 short-form platforms, since bars top and bottom look unpolished. If your source doesn't have your subject centered, reframe with cropping software that lets you choose the crop position, rather than relying on a dead-center crop.
Why are my letterbox bars uneven when I try it manually?
If bars come out uneven, the canvas usually isn't being centered — check that padding is split evenly on both sides (top/bottom or left/right), which is what this calculator assumes and outputs.
Can I use this for photos as well as video?
Yes — the math is purely about pixel dimensions and aspect ratio, so it works identically whether you're cropping a video frame or a still image.