Aspect Ratio Calculator — Pixel dimensions for video, photos & monitors

This aspect ratio calculator helps you match widths and heights so your images, videos, prints, and monitor layouts fit without stretching or unwanted cropping. An aspect ratio describes the relationship between width and height, like 16:9 for widescreen video, 3:2 for many DSLR photos, 4:5 for portrait social posts, or 21:9 for ultrawide monitors.

The idea is simple: if you know the ratio and one dimension, you can calculate the other. For example, a 1920 pixel wide video at 16:9 will be 1080 pixels tall, while a 9:16 vertical clip that is 1080 pixels wide will be 1920 pixels tall. The preview changes shape as you edit, so you can see the difference between square, vertical, widescreen, photo, print, and ultrawide formats.

The Aspect Ratio Formula

• To find Height: Height = Width / (Ratio W / Ratio H)
• To find Width: Width = Height * (Ratio W / Ratio H)
• To find the decimal ratio: Decimal ratio = Width / Height

Step-by-step

1. Choose a preset ratio like 16:9, 9:16, 1:1, 4:5, 3:2, 5:4, 1.414:1, 21:9, or 32:9, or type in a custom ratio.
2. Enter either the pixel width or the pixel height.
3. The calculator fills in the other dimension instantly and shows the computed ratio.
4. Watch the preview resize to confirm the format visually.

Use the deliverables table as a quick reference for common resolutions like 1280×720, 1920×1080, 3840×2160 (UHD), 1080×1350, 6000×4000, 2560×1080, or 5120×1440. This is especially helpful when a client requests “4K,” a print crop, an Instagram portrait, or an ultrawide wallpaper and you need to confirm the exact dimensions.

Real-world use cases include resizing a YouTube thumbnail, preparing Instagram or TikTok posts, planning a film deliverable, cropping a DSLR photo, making ISO paper artwork, or creating a wallpaper for an ultrawide gaming monitor. If you are exporting for video, it is often best to use even pixel counts to avoid encoder padding. If you enter an odd number, rounding to the nearest even value usually prevents alignment issues with common codecs.

Everything runs locally in your browser, so it is fast and private. Once the page is loaded, you can use it offline, which makes it handy on set, in a classroom, or while traveling. The goal is to give you an accurate, easy way to calculate aspect ratios and dimensions so your final output looks exactly as expected.