Aspect Ratio Calculator
Enter any width and height to find the simplified aspect ratio, solve a missing dimension, and preview the shape — for images, video, screens and print.
Updated
What is the Aspect Ratio Calculator?
An aspect ratio is the proportional relationship between an image, video or screen's width and its height, written as width:height — for example, 16:9. It describes the shape of the rectangle, not its size: a 1920×1080 video and a 1280×720 video share the same 16:9 ratio.
This calculator has two modes. Calculate Ratio takes any width and height and returns the simplified whole-number ratio, its decimal value and the nearest industry standard. Solve Dimensions finds a missing width or height when you know one side and the target ratio — the easiest way to resize without stretching anything.
Ratios are unitless, so the tool works identically with pixels, inches or centimeters. Enter photo dimensions in pixels, a print size in inches or a screen size in any unit and you will get the same shape back. Use the unit switcher above the presets so your result labels match what you typed.
Common aspect ratios
| Ratio | Decimal | Typical use |
|---|---|---|
| 16:9 | 1.778 | HDTV, YouTube, most monitors and Full HD / 4K video |
| 9:16 | 0.5625 | Vertical video — Shorts, Reels, TikTok, phone screens |
| 4:3 | 1.333 | Classic TV, older monitors, some tablet screens |
| 1:1 | 1.0 | Square posts and profile pictures |
| 3:2 | 1.5 | Classic 35mm photography and 6×4 in prints |
| 4:5 | 0.8 | Instagram portrait posts (1080×1350 px) |
| 21:9 | 2.333 | Ultrawide monitors and cinematic desktop video |
Need more than a ratio? The Resolution Calculator adds megapixels, PPI and print sizes, the Image Size Finder reads dimensions straight from an uploaded photo, and the Image Resizer resizes the actual file once you know the shape you need.
How it works
The formula
ratio decimal = width ÷ height
simplified ratio = width ÷ GCF : height ÷ GCF
GCF is the greatest common factor of the two numbers. The calculator shows each step under the result, so you can see exactly how your dimensions reduce.
Calculate a ratio from width and height
- Select Calculate Ratio.
- Enter the width and height in any consistent unit — pixels for screens, inches for print.
- Read the simplified ratio (e.g.
16:9), the decimal (e.g.1.778) and the nearest standard.
Worked example — a Full HD frame, 1920×1080:
1920 ÷ 1080 = 1.778
GCF of 1920 and 1080 = 120
1920 ÷ 120 = 16, 1080 ÷ 120 = 9 → 16:9
Find a missing width or height
- Select Solve Dimensions and choose whether the width or height is missing.
- Enter the dimension you know and the target ratio.
- The tool applies
missing = known × (target side ÷ known side).
Worked example — you have a 1280 px wide image that must stay 16:9:
height = 1280 × (9 ÷ 16) = 720 px
Pixels, inches and screens
- Pixels and resolutions: enter pixel dimensions directly.
3840×2160simplifies to16:9,1080×1350to4:5. For density and print-size math, see the PPI Calculator. - Inches and print: because ratios are relative,
10×8inches gives5:4exactly as2500×2000pixels would. Check that your print dimensions match your photo's ratio before ordering prints to avoid unexpected cropping. - Screens and video: match content to the display —
16:9for HDTV and desktop,9:16for vertical phone video. Letterboxing or stretching appears whenever the two shapes differ.
Examples
Calculate 1080p Ratio
Finding the ratio for a standard Full HD resolution.
Width: 1920, Height: 108016:9 (1.778)Solve for Height
Maintaining a 16:9 ratio for a 1280px wide image.
Width: 1280, Target Ratio: 16:9Height: 720pxInstagram Portrait
Checking the ratio of a 1080x1350 image.
Width: 1080, Height: 13504:5 (0.800)Print Size in Inches
Checking whether a print size matches a photo's shape.
Width: 10 in, Height: 8 in5:4 (1.250)Frequently asked questions
How do I calculate aspect ratio from width and height?
How do I calculate aspect ratio from width and height?
Divide the width by the height for the decimal value, then divide both numbers by their greatest common factor (GCF) to get the simplified ratio. For example, 1920×1080 gives 1920 ÷ 1080 = 1.778, and with a GCF of 120 it simplifies to 16:9. This calculator shows each step automatically.
What is the aspect ratio of 1920 × 1080?
What is the aspect ratio of 1920 × 1080?
1920 × 1080 is 16:9 (decimal 1.778) — the Full HD widescreen standard used for HDTV, YouTube and most monitors. Its greatest common factor is 120: 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9.
What does 16:9 mean?
What does 16:9 mean?
16:9 means the width is 16 units for every 9 units of height (about 1.778 times as wide as it is tall). It is the international standard for HDTV, digital television and most modern monitors. Common 16:9 resolutions include 1280×720, 1920×1080 and 3840×2160.
What is the 4:3 aspect ratio?
What is the 4:3 aspect ratio?
4:3 means the width is 4 units for every 3 units of height (decimal 1.333). It was the standard for classic television and older computer monitors, and it still appears on some tablets and projectors. A 1920×1440 image is a typical 4:3 example.
How do I find a missing width or height for a given ratio?
How do I find a missing width or height for a given ratio?
Use the calculator's Solve Dimensions mode: enter the dimension you know plus the target ratio, and it computes the other side. Manually, multiply the known side by the ratio fraction — for a 1280 px wide image at 16:9, height = 1280 × (9 ÷ 16) = 720 px.
How do I calculate the aspect ratio of an image or photo?
How do I calculate the aspect ratio of an image or photo?
Enter the image's pixel dimensions into the width and height fields — for a phone photo that might be 4032×3024, which simplifies to 4:3. If you don't know the dimensions, the Image Size Finder can read them from the file first.
Can I calculate aspect ratio in pixels?
Can I calculate aspect ratio in pixels?
Yes — pixels are the most common input. Enter values like 1920 and 1080 exactly as they appear in your file or camera settings. The simplified ratio is identical whether you measure in pixels, inches or centimeters, because only the proportion matters.
Can I use inches or centimeters, for example for print?
Can I use inches or centimeters, for example for print?
Yes. Select inches or centimeters in the unit switcher and enter your print dimensions — 10×8 inches simplifies to 5:4, and a classic 6×4 inch photo is 3:2. Compare the print ratio with your photo's ratio before printing to avoid cropped edges.
What aspect ratio should I use for screens and video?
What aspect ratio should I use for screens and video?
Use 16:9 for HDTV, desktop video and YouTube, 9:16 for vertical phone video (Shorts, Reels, TikTok) and 21:9 for ultrawide monitors. Whenever the content ratio and the screen ratio differ, the player must letterbox, crop or stretch — matching them avoids all three.
Why does my image look stretched?
Why does my image look stretched?
Images stretch when they are resized without preserving the original ratio — for example, forcing a 4:3 photo into a 16:9 frame. Find the missing dimension with Solve Dimensions instead of guessing, so width and height stay proportional.
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