How to Use This Calculator
- Enter any two of the three values: the aspect ratio (for example 16 : 9), the width, or the height. You can also tap a preset such as 16:9 or 4:5.
- The missing value is filled in automatically and highlighted.
- Read the result: the simplified ratio, its decimal form (16:9 = 1.78:1), the orientation, and, when it helps, the nearest common ratio.
The field you edited longest ago is the one that gets recalculated. Type a width and height to get the ratio. Type a ratio and a width to get the height.
What Is Aspect Ratio?
Aspect ratio is the proportion between the width and the height of a rectangle, written as width : height. A 2:1 frame is twice as wide as it is tall, and a 1:1 frame is a square.
The ratio has no units. A 6 × 4 inch print, a 15 × 10 cm print, and a 1500 × 1000 pixel image all share the same 3:2 shape.
How to Calculate Aspect Ratio
Divide the width and the height by their greatest common divisor (GCD), the largest number that divides both exactly.
Example: 2560 × 1440
- GCD(2560, 1440) = 160
- 2560 ÷ 160 = 16 and 1440 ÷ 160 = 9
- Aspect ratio = 16:9
Decimal sizes work the same way once you scale them to whole numbers. A US Letter sheet is 8.5 × 11 inches. Multiply by 10 to get 85 × 110. The GCD is 5, so the ratio is 17:22.
To express a ratio as a single number, divide width by height: 16 ÷ 9 ≈ 1.78, often written 1.78:1.
How to Resize Without Distortion
Keep the ratio fixed and solve for the missing side:
- Height = width × B ÷ A
- Width = height × A ÷ B
where the ratio is A:B.
Example: a 1600 × 1200 photo (4:3) resized to 1000 pixels wide needs a height of 1000 × 3 ÷ 4 = 750 pixels. Any other height will stretch or squash the image.
If the result isn’t a whole number (16:9 at 1000 pixels tall gives a width of 1777.78), round to the nearest pixel. The distortion is invisible.
Common Aspect Ratios and Where They’re Used
| Ratio | Decimal | Typical use |
|---|---|---|
| 1:1 | 1.00 | Square social posts, profile pictures |
| 4:5 | 0.80 | Tallest portrait feed post on Instagram (feed images range from 4:5 to 1.91:1) |
| 4:3 | 1.33 | Most smartphone photos, classic TV, Micro Four Thirds cameras |
| 3:2 | 1.50 | 35 mm film and most DSLR and mirrorless cameras, 6 × 4 prints |
| 16:9 | 1.78 | HD and 4K video, YouTube, presentations |
| 9:16 | 0.56 | Vertical video: Stories, Reels, Shorts, TikTok |
| 1.85:1 | 1.85 | ”Flat” widescreen cinema |
| 2.39:1 | 2.39 | ”Scope” anamorphic cinema |
| 21:9 | 2.33 | Marketing name for ultrawide formats (really 64:27 or 43:18) |
Landscape, Portrait, and Square
- Landscape: width is greater than height (16:9, 3:2).
- Portrait: height is greater than width (9:16, 4:5). A portrait ratio is a landscape ratio turned on its side.
- Square: width equals height (1:1).
Sources
- International Telecommunication Union. Recommendation ITU-R BT.709: Parameter values for the HDTV standards for production and international programme exchange.
- YouTube Help. Video resolution & aspect ratios.
- Meta for Developers. IG User Media — Image Specifications.