Aspect Ratio Calculator
Resize an image or video while preserving its proportions — and find the simplified aspect ratio (like 16:9, 4:3, or 21:9) of any dimensions. This free online other calculator runs entirely in your browser — no signup, no data sent anywhere.
Inputs
Results
How It Works (Formula & Method)
The simplified ratio is found by dividing both dimensions by their greatest common divisor. For example, GCD(1920, 1080) = 120, so 1920/120 : 1080/120 = 16:9. To resize, the new height = (new width × original height) ÷ original width — preserving the original width-to-height proportion.
Worked Example
Below is a worked example using the calculator's default values. The same numbers are pre-filled in the form above so you can press Calculate and see the result without typing anything.
Inputs used:
- Original Width (px): 1920
- Original Height (px): 1080
- New Width (px): 1280
With these inputs, the calculator computes the metrics shown in the Results panel. Change any value and press Calculate again to see how the result responds — the live widget and the chart both update instantly.
About the Aspect Ratio Calculator
Aspect ratio is the ratio of width to height for a rectangular shape — a screen, image, or video frame. Common ratios you encounter daily: 16:9 (HDTV and most YouTube videos), 4:3 (older TVs and iPads in portrait), 21:9 (ultrawide monitors and cinematic film), 1:1 (Instagram square), 9:16 (vertical phone video and TikTok).
How to Use This Calculator
Enter the original width and height of your image or screen. The calculator simplifies the ratio (so 1920×1080 becomes 16:9). Optionally enter a new desired width and the calculator computes the new height that preserves the aspect ratio — useful for resizing without distortion.
Tips & Considerations
- Common aspect ratios at a glance: 16:9 = 1.778, 4:3 = 1.333, 21:9 = 2.33, 1:1 = 1.0, 9:16 = 0.5625.
- Cropping vs. resizing: this calculator preserves the ratio. To fit different ratios, you need to crop, letterbox, or stretch.
- When designing for social media: Instagram feed = 1:1 or 4:5, Stories = 9:16, YouTube thumbnails = 16:9, Twitter card = 2:1.
- For print, ratios change again: A4 paper is √2:1 (about 1.41:1), letter is roughly 17:22.
Frequently Asked Questions
What does 16:9 mean?
The width is 16 units for every 9 units of height — so a 16:9 screen at 1600 pixels wide is 900 tall.
How do I convert between ratios without distortion?
You cannot — different ratios require either cropping (removing content) or letterboxing (adding black bars).
Is 1.78:1 the same as 16:9?
Yes — 16 ÷ 9 ≈ 1.778. Cinematographers tend to write decimal ratios; consumer media tends to write integer ratios.
What does the Aspect Ratio Calculator compute?
The Aspect Ratio Calculator takes 3 input values and returns 3 results. Calculate aspect ratios and resize images, videos, or screens while preserving proportions. Returns simplified ratio (like 16:9) and new dimensions.