Crop Video

Turn a landscape video into a square or vertical clip for Instagram, Reels, Shorts or TikTok, remove black bars, or cut away an unwanted edge. Choose a ratio and where the kept area sits — or type an exact pixel box — and a preview frame shows the result with the kept area outlined before you commit. Cropping runs in your browser with ffmpeg; your video is never uploaded.

How to use this tool

1. Choose a video: a preview frame appears with the kept area outlined in yellow.
2. Pick the shape (1:1, 9:16, 4:5, 16:9 …), a custom ratio, or an exact box in pixels, and press Calculate to update the preview.
3. Choose the position of the kept area, and a crop size below 100% to zoom in.
4. When the box is right, untick "Preview only" and press Calculate to crop the video.

Formula

Largest box with ratio r: if W ÷ H > r then h = H, w = H × r; otherwise w = W, h = W ÷ r

W × H is the picture as it is displayed (phone videos are turned upright first). Sizes and positions are rounded down to even numbers because H.264 stores colour at half resolution. The position spreads the leftover space: centre splits it evenly, left or top keeps none on that side. The crop size scales the box around the chosen position.

Example

A 1920 × 1080 clip cropped to 9:16 at the centre: 1920 ÷ 1080 = 1.78 is wider than 0.5625, so h = 1080 and w = 1080 × 9 ÷ 16 = 607.5 → 606 pixels, placed at x = (1920 − 606) ÷ 2 = 657, rounded to 656. The result is a 606 × 1080 vertical video.