How to Calculate Aspect Ratio for Video
Need to resize a video but keep the right proportions? Calculate the missing dimension from any aspect ratio instantly.
Quick Answer
Enter one dimension (width or height) and your aspect ratio into the free calculator at dotsapps.com. It calculates the other dimension automatically. Works for 16:9, 4:3, 21:9, or any custom ratio.
Common Video Aspect Ratios
Here are the standard aspect ratios used in video:
- 16:9 — Standard widescreen. YouTube, TV, most monitors. (1920×1080, 1280×720)
- 4:3 — Classic TV format. Still used in some presentations.
- 21:9 — Ultrawide cinematic. Movies and ultrawide monitors.
- 9:16 — Vertical video. TikTok, Instagram Reels, YouTube Shorts.
- 1:1 — Square. Instagram posts, some social ads.
The most common is 16:9. If you are making content for the web, start with 16:9 unless you have a specific reason to use something else.
How to Calculate Missing Dimensions
If you know the width and aspect ratio, calculate the height with this formula:
Height = Width ÷ (Aspect Width ÷ Aspect Height)
For example, a 16:9 video at 1280px wide: 1280 ÷ (16 ÷ 9) = 720px tall.
Instead of doing the math, use the aspect ratio calculator at dotsapps.com. Enter the width, select or type the ratio, and the tool gives you the height instantly. Or enter the height to get the width.
16:9 Resolution Reference Table
Here are all common 16:9 resolutions:
- 7680 × 4320 — 8K
- 3840 × 2160 — 4K UHD
- 2560 × 1440 — 1440p (QHD)
- 1920 × 1080 — 1080p Full HD
- 1280 × 720 — 720p HD
- 854 × 480 — 480p SD
- 640 × 360 — 360p
These numbers are useful when exporting video, setting up streaming, or creating web containers for embedded video.
Aspect Ratios for Social Media Videos
Each platform has preferred video dimensions:
- YouTube: 16:9 (1920×1080 recommended)
- TikTok: 9:16 (1080×1920)
- Instagram Reels: 9:16 (1080×1920)
- Instagram Feed: 1:1 (1080×1080) or 4:5 (1080×1350)
- Twitter/X: 16:9 (1280×720 minimum)
- LinkedIn: 16:9 or 1:1
Use the calculator to find exact pixel dimensions for any ratio. Enter 1080 as the width for vertical platforms, or 1920 for horizontal ones.
How to Do It: Step-by-Step
- 1
Open the free Aspect Ratio Calculator at dotsapps.com.
- 2
Enter one dimension — either width or height in pixels.
- 3
Select or enter your target aspect ratio (e.g., 16:9).
- 4
The tool calculates the missing dimension instantly.
- 5
Use the calculated dimensions for your video export or container.
Frequently Asked Questions
What aspect ratio is 1920x1080?
1920×1080 is a 16:9 aspect ratio. This is standard Full HD (1080p) and the most common video resolution for web and TV content.
How do I find the aspect ratio of an image or video?
Divide the width by the height. If 1920÷1080 = 1.777, that is 16:9. Enter both dimensions into the calculator and it shows the ratio.
What is the best aspect ratio for YouTube?
16:9 at 1920×1080 (1080p) or 3840×2160 (4K). YouTube's player is 16:9, so other ratios will have black bars.
How do I maintain aspect ratio when resizing?
Lock the aspect ratio in the calculator, then change one dimension. The other dimension adjusts automatically to maintain the same proportions.
What aspect ratio is best for TikTok?
9:16 at 1080×1920 pixels. This fills the entire phone screen vertically. Horizontal videos will appear small with black bars.
Ready to Try It?
Aspect Ratio Calculator is free, private, and works right in your browser. No sign-up needed.
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