Aspect Ratio Calculator
Resize while keeping the proportions. Enter a width or height and get the matching dimension for 16:9, 4:3 or any custom ratio.
How to use it
- Pick a preset or type your own ratio.
- Change either width or height — with the lock on, the other follows.
- The preview shows the shape at a glance.
Examples
| 16:9 at 1920 px wide | 1080 px tall |
Enter a target ratio and one dimension, and this works out the matching dimension that keeps the proportions exact — the calculation behind resizing an image or video frame without distorting it.
Common ratios and what they're for
| Ratio | Common use |
|---|---|
| 16:9 | Widescreen video, most monitors and TVs, YouTube |
| 4:3 | Older TVs and monitors, some presentation slides |
| 1:1 | Square social media posts (Instagram) |
| 9:16 | Vertical video — Reels, TikTok, Stories |
| 3:2 | Standard photography sensor ratio (DSLR/mirrorless) |
| 21:9 | Ultrawide monitors, cinematic video |
Why locking the ratio matters
Resizing an image or video frame by width and height independently distorts it — stretching or squashing the content. Locking the ratio means changing one dimension recalculates the other automatically, so a 1920px-wide 16:9 frame always pairs with exactly 1080px tall, keeping everything in proportion.
Custom ratios
Beyond the presets, any custom ratio can be entered directly — useful for print sizes, non-standard screens, or matching an existing asset's proportions when the exact ratio isn't one of the common named ones.
Last updated 17 August 2026