How to scale a resolution by percentage (without half-pixels)
Updated 2026-06-21
Scaling a resolution by a percentage keeps the aspect ratio intact: you multiply both the width and the height by the same factor. The trick is choosing a percentage that lands on whole — ideally even — pixels.
Scaling keeps the ratio
To scale 1920×1080 to 50%, multiply both dimensions by 0.5:
- Width: 1920 × 0.5 = 960
- Height: 1080 × 0.5 = 540
The result, 960×540, is still 16:9. Scaling by a single factor can never distort the shape, which is why "scale by percentage" is the safe way to resize.
Why even pixels matter for video
Most video is encoded with 4:2:0 chroma subsampling, which stores colour at half resolution horizontally and vertically. That requires even width and height — an odd dimension forces the encoder to pad or round, which can cause artifacts or outright rejection by some tools.
For 1920×1080, scales like 50% (960×540) and 75% (1440×810) stay even and clean, while 66.7% (1280×720) is also exactly two-thirds. A scale that lands on a fractional or odd pixel is a warning sign.
Common upscales and downscales
- 1080p → 4K is exactly 200% (1920×1080 → 3840×2160).
- 4K → 1080p is 50%.
- 1080p → 720p is 66.7% (two-thirds).
Upscaling can't invent detail that wasn't captured, but the target dimensions and ratio are exact.
Do it visually
The Resolution Scale & Aspect Ratio Calculator has a percentage scaler — drag a slider or tap 25/50/75/100/150/200% — plus a "pixel-clean scales" list that flags which percentages keep both dimensions even. It also reduces any width×height to its simplest ratio and crops one image to every platform at once, all locally.