Aspect Ratio Calculator
Auto-calculate optimal aspect ratio from width and height
Enter Width/Height
Select a preset or enter a custom ratio
Enter either width or height, and the other will be calculated automatically
Calculation Result
What is the Aspect Ratio Calculator?
A tool to calculate the width-to-height ratio of images and videos. It features two modes: find the aspect ratio of existing image sizes, or calculate the required dimensions for a specific ratio.
Mode 1: Calculate Aspect Ratio
Enter width and height, and the tool automatically simplifies them to clear ratios like 16:9 or 4:3. Using the Greatest Common Divisor (GCD), dimensions like 1920×1080 become 16:9. You'll also see the decimal format (1.78) at the same time.
Mode 2: Calculate Dimensions
Choose from common presets like 16:9 or 4:3, enter either width or height, and the other dimension is calculated automatically. Custom ratio input is also supported for flexible handling of special aspect ratios.
How to Use
Find an Aspect Ratio
- Select the "Calc Ratio" tab
- Enter width and height (e.g., 1920 × 1080)
- The simplified ratio (16:9) and decimal value (1.78) appear
Calculate Required Dimensions
- Select the "Calc Dimensions" tab
- Choose a ratio from presets or enter a custom ratio
- Enter either width or height
- The other dimension is calculated automatically
When This Tool is Useful
When editing video with Full HD (1920×1080) footage, you can instantly confirm the aspect ratio is 16:9. Conversely, for a square Instagram post (1:1) at 1080px width, you'll immediately know the height is also 1080px.
Practical examples:
- For a YouTube thumbnail (16:9) at 720px height, calculate that 1280px width is needed
- When creating vertical smartphone video (9:16), determine that 1080px width requires 1920px height
- Check if a design element matches a 3:2 ratio by entering its width and height
How the Calculation Works
Dividing both width and height by their Greatest Common Divisor (GCD) simplifies the ratio to its simplest form.
For 1920 × 1080:
GCD(1920, 1080) = 120
1920 ÷ 120 = 16
1080 ÷ 120 = 9
→ 16:9
Dimension calculations maintain the chosen ratio while computing one value from the other.
For 16:9 at 1920px width:
Height = (1920 × 9) ÷ 16 = 1080px
For 16:9 at 720px height:
Width = (720 × 16) ÷ 9 = 1280px
Common Ratio Reference
| Ratio | Decimal | Primary Use |
|---|---|---|
| 16:9 | 1.78 | YouTube, Full HD, 4K video |
| 4:3 | 1.33 | Older TVs, projectors |
| 1:1 | 1.00 | Instagram square, profile pics |
| 21:9 | 2.33 | Cinema, ultrawide monitors |
| 9:16 | 0.56 | TikTok, Instagram vertical |
| 3:2 | 1.50 | DSLR cameras, L-size prints |
| 16:10 | 1.60 | Laptop screens, MacBook display |
FAQ
Why display 16:9 instead of 1920:1080?
Large numbers like 1920:1080 are harder to grasp intuitively. Dividing both by the GCD of 120 reveals the essential ratio of 16:9, which is much clearer.
What's the decimal format (like 1.78) used for?
It's handy for CSS aspect-ratio property with numeric values, or for calculations in code. Remembering "16:9 is about 1.78" also makes it easier to compare ratios numerically.
How do I enter custom ratios?
Select "Custom" in "Calc Dimensions" mode to input width and height ratios separately. This supports special ratios like 5:4 or 21:10.