Aspect Ratio Scaling

Aspect ratio tells you how width and height should compare so an image or shape does not look stretched. If the ratio is given as width:height = r_w:r_h, then keeping that same proportion means the height must scale by the same factor as the width, which gives h = w × (r_h / r_w). This is just proportional reasoning: multiply the width by the height-to-width fraction of the ratio.

Use this when resizing photos, videos, screens, posters, or any rectangular object while keeping its shape unchanged. It is also useful in design and printing when you know one side and need the matching side from a fixed ratio.

• swapping the ratio terms and using rw/rh instead of rh/rw
• using the wrong side as the starting value, such as treating height like width
• forgetting that the ratio must stay in the same order as written