Aspect Ratio Calculator
Calculate and keep aspect ratios for screens, photos and video
Aspect ratio = width ÷ GCD : height ÷ GCD. 1920 × 1080 reduces to 16:9 because both sides divide by 120. To resize, new height = new width × height ÷ width.
Aspect ratio calculator
LiveResize and keep the ratio
How to calculate an aspect ratio
An aspect ratio describes the shape of a rectangle, not its size. It compares width with height, written as two whole numbers with a colon, such as 16:9, or as a single decimal, such as 1.7778. Two images with the same ratio have the same shape, so one can be scaled to the other without stretching or cropping. Pixel, print and typography units for the same work are gathered on the digital converter hub.
To turn a resolution into its simplest ratio, divide both sides by their greatest common divisor (GCD), the largest whole number that divides both exactly. To resize, keep the ratio fixed and solve for the missing side.
Step by step: 1920 × 1080
- Find the GCD with Euclid's method: 1,920 mod 1,080 = 840; 1,080 mod 840 = 240; 840 mod 240 = 120; 240 mod 120 = 0. The last non-zero remainder, 120, is the GCD.
- Divide both sides by it: 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9, so the ratio is 16:9.
- For the decimal form, divide width by height: 1920 ÷ 1080 = 1.7778.
- To resize to 1,280 px wide, multiply by the height and divide by the width: 1280 × 1080 ÷ 1920 = 720, giving 1280 × 720.
The calculator above does all four steps at once. Pick a preset to lock a ratio, then type either new dimension. For physical sizes of the result, convert with the pixels to inches converter.
Common aspect ratios, drawn to scale
How do I calculate aspect ratio in Excel or Google Sheets?
With the width in A2 and the height in B2, enter =A2/GCD(A2,B2)&":"&B2/GCD(A2,B2); for 1920 and 1080 it returns 16:9.
GCD returns the greatest common divisor in both Excel and Google Sheets, so the same formula reduces any whole-number resolution. These companions cover the other jobs, shown for A2 = 1920 and B2 = 1080:
| Result | Formula | Example |
|---|---|---|
| Decimal ratio | =ROUND(A2/B2,4) | 1.7778 |
| Height for a new width in C2 | =C2*B2/A2 | C2 = 1280 → 720 |
| Width for a new height in C2 | =C2*A2/B2 | C2 = 1440 → 2,560 |
| Nearest even height for video | =2*ROUND(C2*B2/A2/2,0) | C2 = 1000 → 562 (exact 562.5) |
GCD works on whole numbers only, so round measured sizes first. A ratio that does not reduce neatly still comes out exact: 1366 × 768 returns 683:384, and its decimal, 1.7786, shows that it is close to 16:9 (1.7778) without matching it.
How wide is a 55-inch 16:9 TV?
A 55-inch 16:9 TV is about 47.94 in wide and 26.96 in tall, because width = diagonal × 16 ÷ √(16² + 9²) and height = diagonal × 9 ÷ √(16² + 9²).
Screens are sold by their diagonal, so the ratio decides the rest, and the same formula works for any shape once you swap in its two numbers. The sizes below cover the visible picture only, so add the bezel and stand when you plan a wall or a cabinet:
| 16:9 diagonal | Width | Height | Metric |
|---|---|---|---|
| 24 in | 20.92 in | 11.77 in | 53.1 × 29.9 cm |
| 27 in | 23.53 in | 13.24 in | 59.8 × 33.6 cm |
| 32 in | 27.89 in | 15.69 in | 70.8 × 39.8 cm |
| 43 in | 37.48 in | 21.08 in | 95.2 × 53.5 cm |
| 55 in | 47.94 in | 26.96 in | 121.8 × 68.5 cm |
| 65 in | 56.65 in | 31.87 in | 143.9 × 80.9 cm |
| 75 in | 65.37 in | 36.77 in | 166 × 93.4 cm |
| 85 in | 74.08 in | 41.67 in | 188.2 × 105.8 cm |
Ratio matters as much as diagonal. A 34-inch ultrawide at 3440 × 1440 (43:18) measures 31.36 × 13.13 in, almost the same height as a 27-inch 16:9 monitor (23.53 × 13.24 in) but 33% wider. The inches to cm converter handles other sizes, and the picture area of a 55-inch set, 1,293 square inches, can be turned into other units with the area converter.
What aspect ratio should I use for YouTube, Instagram and TikTok?
Use 16:9 at 1920 × 1080 for YouTube and other landscape video, 9:16 at 1080 × 1920 for Reels, TikTok and Shorts, and 4:5 at 1080 × 1350 for portrait Instagram feed posts.
These frames match how each app fills a phone screen: 9:16 fills a typical phone held upright, and 4:5 takes up more of a scrolling feed than a square or landscape post. Square 1:1 posts at 1080 × 1080 still display everywhere, which makes them the safest choice when one image has to serve several platforms.
When you reuse one shot across platforms, plan for the crop. This is how much of the original frame survives:
| Shot in | Cropped to | You keep |
|---|---|---|
| 16:9 landscape | 1:1 square | 56.25% of the width |
| 16:9 landscape | 4:5 portrait | 45% of the width |
| 16:9 landscape | 9:16 vertical | 31.64% of the width |
| 4:5 portrait | 1:1 square | 80% of the height |
| 9:16 vertical | 4:5 portrait | 70.31% of the height |
Platforms revise their recommended upload sizes from time to time, so check each app's current guide before a large campaign.
Common resolutions and their aspect ratios
Ratios are reduced exactly using the greatest common divisor of width and height.
| Name | Resolution | Aspect ratio | Decimal |
|---|---|---|---|
| HD (720p) | 1280 × 720 | 16:9 | 1.7778 |
| Full HD (1080p) | 1920 × 1080 | 16:9 | 1.7778 |
| QHD (1440p) | 2560 × 1440 | 16:9 | 1.7778 |
| 4K UHD | 3840 × 2160 | 16:9 | 1.7778 |
| 8K UHD | 7680 × 4320 | 16:9 | 1.7778 |
| WUXGA | 1920 × 1200 | 8:5 | 1.6 |
| UW-QHD ultrawide | 3440 × 1440 | 43:18 | 2.3889 |
| XGA | 1024 × 768 | 4:3 | 1.3333 |
| iPad (10th gen) | 2360 × 1640 | 59:41 | 1.439 |
| Instagram portrait | 1080 × 1350 | 4:5 | 0.8 |
| Vertical video (Reels, TikTok, Shorts) | 1080 × 1920 | 9:16 | 0.5625 |
| DCI 4K (cinema) | 4096 × 2160 | 256:135 | 1.8963 |
16:9 vs 4:3: what is the difference?
These are the two ratios people compare most often: the widescreen shape of modern TVs and monitors, and the older shape of classic television and many tablets.
| Attribute | 16:9 | 4:3 |
|---|---|---|
| Decimal ratio | 1.7778 | 1.3333 |
| Width at 1,080 px tall | 1,920 px | 1,440 px |
| Common resolutions | 1280 × 720, 1920 × 1080, 3840 × 2160 | 640 × 480, 1024 × 768, 1600 × 1200 |
| Standard or origin | ITU-R BT.709 (HDTV) and BT.2020 (UHDTV) | Standard-definition TV and early VGA and XGA computer displays |
| Typical uses today | TVs, monitors, laptops, YouTube | SD archive footage, older iPads, Micro Four Thirds camera sensors |
4 key differences
- At the same height, a 16:9 frame is 33.33% wider than a 4:3 frame.
- At the same diagonal, a 4:3 screen has 12.33% more picture area than a 16:9 screen.
- A 16:9 picture shown full-width on a 1024 × 768 (4:3) display is 576 px tall, filling 75% of the height and leaving 96 px bars above and below.
- 16:9 (1.78) lies close to the geometric mean of 4:3 and 2.35:1 cinema (1.77), so both older formats fit on it with bars of similar size.
Width and height for common aspect ratios
Heights calculated as width × second number ÷ first number. Non-integer heights, such as 21:9 at 640 px, are shown to two decimals; round them to a whole (and, for video, even) number of pixels.
| Ratio | 640 wide | 1280 wide | 1920 wide | 3840 wide |
|---|---|---|---|---|
| 16:9 | 640 × 360 | 1,280 × 720 | 1,920 × 1,080 | 3,840 × 2,160 |
| 4:3 | 640 × 480 | 1,280 × 960 | 1,920 × 1,440 | 3,840 × 2,880 |
| 21:9 | 640 × 274.29 | 1,280 × 548.57 | 1,920 × 822.86 | 3,840 × 1,645.71 |
| 1:1 | 640 × 640 | 1,280 × 1,280 | 1,920 × 1,920 | 3,840 × 3,840 |
| 3:2 | 640 × 426.67 | 1,280 × 853.33 | 1,920 × 1,280 | 3,840 × 2,560 |
| 9:16 | 640 × 1,137.78 | 1,280 × 2,275.56 | 1,920 × 3,413.33 | 3,840 × 6,826.67 |
| 4:5 | 640 × 800 | 1,280 × 1,600 | 1,920 × 2,400 | 3,840 × 4,800 |
Screen, photo and cinema aspect ratios compared
Ratios sorted from squarest to widest, with the decimal value and the height a 1,920 px wide frame would have. Note that the three "21:9" rows are all different shapes.
| Ratio | Decimal | Where it's used | At 1920 wide |
|---|---|---|---|
| 4:3 | 1.3333 | Classic TV, early computer monitors, many iPads | 1,920 × 1,440 |
| 3:2 | 1.5 | 35 mm film and most DSLR and mirrorless sensors | 1,920 × 1,280 |
| 16:10 | 1.6 | Laptops and productivity monitors (1920 × 1200) | 1,920 × 1,200 |
| 16:9 | 1.7778 | HDTV, YouTube, most monitors and phones in landscape | 1,920 × 1,080 |
| 1.85:1 | 1.85 | Flat widescreen cinema | 1,920 × 1,037.8 |
| 256:135 | 1.8963 | DCI 4K cinema container (4096 × 2160) | 1,920 × 1,012.5 |
| 2:1 | 2 | Some streaming series (the Univisium format) | 1,920 × 960 |
| 21:9 (literal) | 2.3333 | Marketing label for ultrawide screens | 1,920 × 822.9 |
| 64:27 | 2.3704 | Ultrawide 2560 × 1080 and 5120 × 2160 | 1,920 × 810 |
| 43:18 | 2.3889 | Ultrawide 3440 × 1440 | 1,920 × 803.7 |
| 2.39:1 | 2.39 | Anamorphic scope cinema | 1,920 × 803.3 |
What are letterboxing and pillarboxing?
Letterboxing adds black bars above and below a picture that is wider than the screen, and pillarboxing adds bars at the sides of a picture that is narrower.
When the source and the screen have different ratios, something has to give. A 2.39:1 film on a 16:9 TV fills the full width but only 74.4% of the height. On a 3840 × 2160 screen the picture is about 1,607 px tall, leaving black bars of about 277 px above and below. This is letterboxing.
The reverse is pillarboxing: a 4:3 video on a 1920 × 1080 screen is scaled to 1,080 px tall, which makes it 1,440 px wide and leaves 240 px bars on each side. The alternatives are cropping, which cuts off part of the image, or stretching, which distorts faces and circles and should be avoided.
Cropping for social media
A 1920 × 1080 landscape frame cropped to 9:16 for vertical video keeps its full 1,080 px height but only 1080 × 9 ÷ 16 = 607.5 px of width, roughly a third of the original frame. Plan vertical shots with the subject in the center third.
Tips and common mistakes
- Marketed ratios are rounded. 1366 × 768 laptops are sold as 16:9, but the exact ratio is 683:384. Ultrawide 3440 × 1440 is 43:18, not 21:9.
- Use even numbers for video. Most H.264 and HEVC encoders using 4:2:0 color need even widths and heights, so round 607.5 to 608, not 607.
- Portrait flips the numbers. 9:16 is the same shape as 16:9 turned on its side. Instagram's 4:5 portrait is 1080 × 1350.
- Pixel ratio is not physical ratio on rare formats with non-square pixels, such as old DV and anamorphic video. Modern cameras, phones and screens use square pixels.
- Keep CSS boxes proportional. The CSS
aspect-ratio: 16 / 9property reserves the right height before an image loads; size fonts and spacing around it with the px to rem converter.
Print sizes use the same logic: an 8 × 10 in print is 4:5, while a 4 × 6 in photo is 2:3, so the same image cannot fill both without cropping. Convert paper sizes with the cm to inches converter.
Sources and further reading
The standards and references behind the numbers on this page. Links open in a new tab.
Further reading
- Aspect ratio (image)Wikipedia
Aspect ratio FAQs
Short, exact answers to what people ask most.
How do I calculate an aspect ratio?
Divide the width and height by their greatest common divisor. For 1920 × 1200 the GCD is 240, so the ratio is 8:5, which is usually marketed as 16:10.
What aspect ratio is 1920 x 1080?
1920 × 1080 is 16:9. Both sides divide by 120, giving 16 and 9, and the decimal ratio is 1.7778.
What resolutions are 16:9?
Common 16:9 resolutions are 1280 × 720 (HD), 1920 × 1080 (Full HD), 2560 × 1440 (QHD), 3840 × 2160 (4K UHD) and 7680 × 4320 (8K).
What aspect ratio is 1080 x 1350?
1080 × 1350 is 4:5, because both sides divide by 270. It is the classic Instagram portrait size for feed posts.
How do I resize an image without distorting it?
Keep the ratio fixed: new height = new width × original height ÷ original width. Shrinking 1920 × 1080 to 1,280 px wide gives 1280 × 720.
Is an ultrawide monitor really 21:9?
Not exactly. 2560 × 1080 is 64:27 (about 2.37:1) and 3440 × 1440 is 43:18 (about 2.39:1). 21:9 is a rounded marketing label for 2.33:1.
What aspect ratio is 2560 x 1440?
2560 × 1440 is 16:9, because both sides divide by 160. It is the QHD, or 1440p, resolution common on 27-inch monitors.
What aspect ratio is 1280 x 1024?
1280 × 1024 is 5:4, because both sides divide by 256. It was a common resolution for 17- and 19-inch LCD monitors in the 2000s.
Related conversions
Television and UHD resolutions from ITU-R BT.709 and BT.2020, the DCI 4K container from the Digital Cinema Initiatives specification, the CSS aspect-ratio property from the W3C CSS Box Sizing Module Level 4, and the GCD function from the Microsoft Excel and Google Sheets documentation. Last updated . How we verify our numbers.