Aspect Ratio Calculator — Pixel dimensions for cinema & social

This aspect ratio calculator helps you match widths and heights so your images and videos fit the format you need without stretching or unwanted cropping. An aspect ratio describes the relationship between width and height, like 16:9 for widescreen video or 4:5 for portrait social posts. When the ratio is correct, your content looks natural on screens, projectors, and social platforms, and you avoid black bars or distorted visuals.

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. This tool automates that math and confirms the exact ratio so you can verify that a “2.39:1” deliverable really is the cinematic scope you intended.

Step-by-step

1. Choose a preset ratio like 16:9, 1:1, 4:3, 4:5, 9:16, or 2.39:1, or type in a custom ratio.
2. Enter either the width or the height in pixels (or any unit you prefer).
3. The calculator fills in the missing dimension instantly and shows the computed ratio.
4. If needed, flip the solve mode to calculate width from height instead of height from width.

Use the deliverables table as a quick reference for common resolutions like 1280×720, 1920×1080, 3840×2160 (UHD), or 4096×2160 (DCI 4K). This is especially helpful when a client requests “4K” and you need to confirm which standard they mean. The preset chips make it easy to jump between social media sizes and cinema formats without hunting for a chart.

Real-world use cases include resizing a YouTube thumbnail, preparing Instagram or TikTok posts, planning a film deliverable, or creating banners and slides that must fit a specific screen. 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.