Aspect Ratio Calculator
Calculate aspect ratios and scale dimensions proportionally. Supports all common ratios: 16:9, 4:3, 1:1, 3:2, and more.
Find Ratio from Dimensions
Simplified Ratio
16:9
Decimal
1.7778
Percentage
56.25%
height / width
Scale Dimensions
Edit one field — the other is calculated automatically (highlighted).
Result
1280 × 720
Height = 720.00px
Visual Preview
100×56
200×113
320×180
What Is an Aspect Ratio Calculator?
An aspect ratio calculator finds the proportional relationship between width and height. Enter any two values and it solves for the third. This is useful for resizing images, designing responsive layouts, setting video dimensions, and converting between screen sizes while preserving proportions.
How to Use
- Find ratio from dimensions: enter width and height to get the simplified ratio
- Scale dimensions: enter a known dimension and a ratio to calculate the missing dimension
- Use presets: click any common ratio (16:9, 4:3, etc.) to pre-fill the ratio fields
Common Aspect Ratios
- 16:9 — HD video, YouTube, most modern monitors and phones (landscape)
- 4:3 — older TVs, tablets, standard photography
- 1:1 — square, used by Instagram posts and profile pictures
- 3:2 — DSLR camera sensor, 35mm film
- 21:9 — ultrawide monitors, cinematic video
- 9:16 — portrait video, TikTok, Instagram Reels, phone screens
FAQ
How is the simplified ratio calculated?
The calculator divides both width and height by their Greatest Common Divisor (GCD). For example, 1920×1080 has a GCD of 120, so the simplified ratio is 16:9 (1920÷120 = 16, 1080÷120 = 9).
How do I resize an image to a specific ratio?
In the "Scale Dimensions" section, select the target ratio and enter your known dimension (either width or height). The calculator solves for the missing dimension, ensuring the image stays within the desired ratio without distortion.
Why does my ratio not simplify to a round number?
Not all dimension pairs have a clean whole-number ratio. For example, 800×450 simplifies to 16:9 (GCD = 50), but 800×451 has no common divisor other than 1, so the ratio stays as 800:451. This is normal — simply round your dimensions to the nearest value that matches your desired ratio.