Aspect Ratio Calculator
To find an aspect ratio, divide the width and the height by the largest number that goes into both: 1920 × 1080 has a greatest common divisor of 120, so it is 16:9. To keep that ratio at a new size, multiply the known side by the ratio: a 1280-pixel-wide 16:9 image is 720 pixels tall, and a 27-inch 16:9 monitor is 23.53 × 13.24 in (59.77 cm × 33.62 cm). Type any width and height for the simplified ratio and the nearest common one (16:9, 16:10, 4:3, 3:2…), or a ratio and one side for the missing one.
Updated Runs in your browser: nothing you enter is uploadedHow this tool works
Worked out in your browser with exact fractions. Ratios can be typed as 16:9, 16/9, 16x9 or 1.78.
What is the aspect ratio of my width and height?
16:9
GCD(1920, 1080) = 120, so 1920 ÷ 120 : 1080 ÷ 120 = 16:9.
- Simplified ratio
- 16:9
- Decimal ratio
- ≈ 1.7778 : 1
- Orientation
- Landscape (wider than tall)
- Nearest common ratio
- 16:9 (the same ratio)
- Total pixels
- 2,073,600 (≈ 2.07 megapixels)
Resize to a ratio: find the missing width or height
1280 × 720
height = 1280 × 9 ÷ 16 = 720
- Ratio
- 16:9
- New height
- 720
Screen size from the diagonal and aspect ratio
23.53 × 13.24 in
width = 27 × 16 ÷ √(16² + 9²) = 23.53 in; height = 27 × 9 ÷ √(16² + 9²) = 13.24 in
- Width
- 23.53 in (59.77 cm)
- Height
- 13.24 in (33.62 cm)
- Diagonal
- 27 in (68.58 cm)
- Screen area
- 311.5 sq in (2,009.68 sq cm)
- Aspect ratio
- 16:9
Common aspect ratios and where they are used
| Ratio | Decimal | Typical use | Size with a 1080 short side |
|---|---|---|---|
| 16:9 | ≈ 1.7778 | HD and 4K TVs, most monitors and phones held sideways, YouTube | 1920 × 1080 |
| 16:10 | 1.6 | Many laptops and some monitors | 1728 × 1080 |
| 4:3 | ≈ 1.3333 | Older TVs and monitors, iPads, many compact cameras | 1440 × 1080 |
| 3:2 | 1.5 | 35 mm film and most DSLR and mirrorless photos, 6×4 in prints | 1620 × 1080 |
| 5:4 | 1.25 | Old 1280×1024 monitors, 8×10 in prints | 1350 × 1080 |
| 1:1 | 1 | Square posts, profile pictures, album covers | 1080 × 1080 |
| 21:9 | ≈ 2.3333 | Ultrawide monitors and widescreen film | 2520 × 1080 |
| 32:9 | ≈ 3.5556 | Super ultrawide monitors | 3840 × 1080 |
| 2:1 | 2 | Some phone screens and panoramic crops | 2160 × 1080 |
| 9:16 | 0.5625 | Stories, Reels, Shorts and TikTok: full-screen vertical video | 1080 × 1920 |
| 3:4 | 0.75 | Portrait photos, iPads held upright | 1080 × 1440 |
| 2:3 | ≈ 0.6667 | Portrait photos, 4×6 in prints held upright | 1080 × 1620 |
| 4:5 | 0.8 | Portrait feed posts | 1080 × 1350 |
Common screen and image resolutions and their aspect ratios
| Name | Resolution | Simplified ratio | Nearest common ratio | Megapixels (rounded) |
|---|---|---|---|---|
| VGA | 640 × 480 | 4:3 | 4:3 (the same ratio) | 0.31 |
| SVGA | 800 × 600 | 4:3 | 4:3 (the same ratio) | 0.48 |
| XGA | 1024 × 768 | 4:3 | 4:3 (the same ratio) | 0.79 |
| HD (720p) | 1280 × 720 | 16:9 | 16:9 (the same ratio) | 0.92 |
| WXGA | 1280 × 800 | 8:5 | 16:10 (the same ratio) | 1.02 |
| Common laptop panel | 1366 × 768 | 683:384 | 16:9 (0.05% wider) | 1.05 |
| HD+ | 1600 × 900 | 16:9 | 16:9 (the same ratio) | 1.44 |
| Full HD (1080p) | 1920 × 1080 | 16:9 | 16:9 (the same ratio) | 2.07 |
| WUXGA | 1920 × 1200 | 8:5 | 16:10 (the same ratio) | 2.30 |
| QHD (1440p) | 2560 × 1440 | 16:9 | 16:9 (the same ratio) | 3.69 |
| Ultrawide Full HD | 2560 × 1080 | 64:27 | 21:9 (1.59% wider) | 2.76 |
| WQXGA | 2560 × 1600 | 8:5 | 16:10 (the same ratio) | 4.10 |
| Ultrawide QHD | 3440 × 1440 | 43:18 | 21:9 (2.38% wider) | 4.95 |
| 4K UHD | 3840 × 2160 | 16:9 | 16:9 (the same ratio) | 8.29 |
| DCI 4K | 4096 × 2160 | 256:135 | 2:1 (5.19% narrower) | 8.85 |
| Super ultrawide QHD | 5120 × 1440 | 32:9 | 32:9 (the same ratio) | 7.37 |
| 5K | 5120 × 2880 | 16:9 | 16:9 (the same ratio) | 14.75 |
| 8K UHD | 7680 × 4320 | 16:9 | 16:9 (the same ratio) | 33.18 |
| Vertical video (Stories, Reels) | 1080 × 1920 | 9:16 | 9:16 (the same ratio) | 2.07 |
| Square post | 1080 × 1080 | 1:1 | 1:1 (the same ratio) | 1.17 |
| Portrait post | 1080 × 1350 | 4:5 | 4:5 (the same ratio) | 1.46 |
| 24 MP camera photo | 6000 × 4000 | 3:2 | 3:2 (the same ratio) | 24.00 |
16:9 screen sizes: width and height from the diagonal
| Diagonal | Width (in) | Height (in) | Width (cm) | Height (cm) |
|---|---|---|---|---|
| 21.5″ | 18.74 | 10.54 | 47.6 | 26.77 |
| 24″ | 20.92 | 11.77 | 53.13 | 29.89 |
| 27″ | 23.53 | 13.24 | 59.77 | 33.62 |
| 32″ | 27.89 | 15.69 | 70.84 | 39.85 |
| 43″ | 37.48 | 21.08 | 95.19 | 53.55 |
| 50″ | 43.58 | 24.51 | 110.69 | 62.26 |
| 55″ | 47.94 | 26.96 | 121.76 | 68.49 |
| 65″ | 56.65 | 31.87 | 143.9 | 80.94 |
| 75″ | 65.37 | 36.77 | 166.04 | 93.39 |
| 85″ | 74.08 | 41.67 | 188.17 | 105.85 |
How to find and keep an aspect ratio
- Divide by the greatest common divisor. Find the largest number that divides both sides exactly (the GCD) and divide each side by it: 1920 × 1080 ÷ 120 = 16:9.
- Compare with a common ratio. If the ratio is not one you know, compare its decimal (width ÷ height) with the common ones: 683:384 is ≈ 1.7786 : 1, close to 16:9 (0.05% wider).
- Solve the missing side. To resize, multiply the known side by the other side of the ratio and divide by its own side: height = width × 9 ÷ 16, so 1280 wide gives 720 tall.
- Check the rounding. When the result is not a whole number, such as 1366 × 768.375 for a 1366-wide 16:9 image, round it or pick a size that is an exact multiple of the ratio: 1360 × 765 or 1376 × 774.
- For a screen, use the diagonal. The diagonal, width and height form a right triangle: width = diagonal × 16 ÷ √(16² + 9²). A 27-inch 16:9 screen is 23.53 × 13.24 in.
Frequently asked questions
- How do I calculate an aspect ratio?
- Divide the width and the height by their greatest common divisor. For 1920 × 1080, GCD(1920, 1080) = 120, so 1920 ÷ 120 : 1080 ÷ 120 = 16:9. If the GCD is 1, the pair is already in lowest terms (1921 × 1080 stays 1921:1080).
- What aspect ratio is 1920×1080, 1440p and 4K?
- All three are 16:9: 1920 × 1080 (Full HD), 2560 × 1440 (QHD) and 3840 × 2160 (4K UHD) each simplify to 16:9. Ultrawide 3440 × 1440 is 43:18, marketed as 21:9.
- How do I resize an image without stretching it?
- Keep the ratio: new height = new width × old height ÷ old width. Resizing a 4000 × 3000 (4:3) photo to 1200 pixels wide gives 1200 × 900. If the result has decimals, round to the nearest whole pixel; the picture will differ by less than one pixel from the original shape.
- What is the aspect ratio of 1366×768?
- Exactly 683:384, because the greatest common divisor is 2. That is ≈ 1.7786 : 1, so the nearest common ratio is 16:9 (0.05% wider): screens sold as 16:9 at this resolution are a fraction of a percent off, as 768 is not a multiple of 9.
- Is 21:9 really 21:9?
- Usually not exactly. Ultrawide monitors marketed as 21:9 are mostly 64:27 (2560 × 1080 is 64:27, ≈ 2.3704 : 1) or 43:18, against 7:3 (2.3333) for a true 21:9. The calculator names the nearest common ratio and shows the difference: 21:9 (1.59% wider).
- What does a ratio like 2.39:1 mean?
- It is the width as a multiple of the height: 2.39 wide for every 1 tall. Type 2.39 (or 2.39:1) and the calculator turns it into 239:100; its nearest common ratio is 21:9 (2.43% wider). Cinema formats are usually quoted this way.
- How do I find the width and height of a TV or monitor from its diagonal?
- The diagonal is the hypotenuse of a right triangle with the ratio's sides. For 16:9, width = diagonal × 16 ÷ √337 and height = diagonal × 9 ÷ √337. A 55-inch 16:9 TV is 47.94 × 26.96 in (121.76 cm wide, 68.49 cm tall), and a 69 cm monitor is 60.14 × 33.83 cm. The frame adds more.
- Can I use decimals, like paper sizes?
- Yes. Sizes are scaled to whole numbers before the divisor is found, so US Letter, 8.5 × 11 inches, is 17:22 (≈ 0.7727 : 1). The nearest common ratio, 3:4 (3.03% wider), shows that it is not one of the screen ratios.
How it works
Widths, heights and ratios are kept as exact fractions of whole numbers, so nothing drifts the way floating-point decimals can. A ratio is found by scaling both sides to whole numbers (when you type decimals), then dividing each by their greatest common divisor, found with Euclid’s algorithm. The nearest common ratio is the one from the list above whose width ÷ height is closest on a logarithmic scale, so 2:1 and 1:2 are equally far from 1:1; the percentage shown is how much wider or narrower your ratio is. Resizing multiplies the known side by the ratio as an exact fraction and rounds only what is displayed; the “closest sizes with exactly this ratio” are the multiples of the simplified ratio either side of your value. Screen sizes take the square root of the sum of the squares of the ratio’s terms, so they are computed in double precision and rounded to two decimals, with 1 inch = 2.54 cm exactly. Sizes describe the visible screen area, not the bezel. Everything runs in your browser.
Sources
- Euclid, Elements, Book VII (the Euclidean algorithm for the greatest common divisor)
- Recommendation ITU-R BT.709, Parameter values for the HDTV standards (16:9 picture aspect ratio)
- NIST Special Publication 811, Guide for the Use of the International System of Units (1 inch = 2.54 cm exactly)
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