Runs in your browser
Aspect Ratio Calculator
Convert between 16:9, 9:16, 4:3, 4:5, 1:1, and 21:9, with pixel dimensions for each.
Aspect ratio
Simplified ratioDecimal 1.7778 (1920 ÷ 1080)
16:9Common match16:9 — standard YouTube player
16:9How it's computed: the ratio is simplified by the greatest common divisor of width and height, then compared with the common ratios. Dimensions scale by the ratio's width ÷ height factor.
Same job, one API call
Runs in your browser — nothing is sent anywhere.
Questions
Which ratio for which YouTube surface?
16:9 for regular uploads, 9:16 for Shorts, 1:1 and 4:5 for feed-friendly crossposts. The player letterboxes anything else.
What if I upload the wrong ratio?
YouTube plays it — the player adds bars to fit the frame rather than rejecting the file. It just looks smaller than a native-ratio upload.
Does 21:9 work on YouTube?
It plays fine and fills ultrawide monitors, but most viewers see letterboxing. Export 16:9 unless the footage was genuinely shot wide.
Related tools
- Video Size CalculatorFile size for any length, resolution, and bitrate — before you commit to the export.
- Video Bitrate CalculatorThe bitrate YouTube recommends for your resolution and frame rate.
- Timecode ConverterFrames to timecode and back at any frame rate, including drop-frame.
- Frame Rate ConverterRuntime and audio pitch change when you conform footage to a different frame rate.