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    Aspect Ratio Calculator

    Calculate the aspect ratio of any width and height. Find equivalent dimensions for resizing without cropping.

    Free to use. Runs in your browser.

    Enter a width and height to calculate the aspect ratio, or lock a ratio (16:9, 4:3, 1:1) and calculate the missing dimension. Useful for images, video, and responsive layouts.

    Understanding Aspect Ratios

    An aspect ratio describes the proportional relationship between width and height. When someone says "16:9", they mean for every 16 units of width, there are 9 units of height. It doesn't matter if those units are pixels, centimetres, or metres, the shape stays the same.

    This matters because resizing an image without maintaining its aspect ratio distorts it. Stretching a 4:3 photo to fit a 16:9 slot squashes faces and warps buildings. The aspect ratio calculator helps you find the right dimensions for any target size while keeping the original proportions intact.

    The calculator reduces your dimensions to the simplest ratio using the greatest common divisor. So 1920×1080 becomes 16:9, and 2560×1440 becomes 16:9 too, they're the same shape at different sizes.

    Common Aspect Ratios

    RatioDecimalCommon ResolutionsUsed For
    1:11.01080×1080, 500×500Instagram posts, profile pictures, app icons
    4:31.3331024×768, 2048×1536iPad displays, classic TV, presentations
    3:21.51080×720, 6000×4000DSLR photos, Surface tablets, 35mm film
    16:91.7781920×1080, 3840×2160Widescreen monitors, YouTube, TV
    16:101.61920×1200, 2560×1600MacBook displays, business monitors
    21:92.3332560×1080, 3440×1440Ultrawide monitors, cinematic displays
    9:160.56251080×1920Instagram/TikTok Stories, mobile video
    2:30.6671000×1500Pinterest pins, book covers, posters

    What this means for you: Before resizing any image, check which aspect ratio your target platform requires. Using the wrong ratio means either distortion or unwanted cropping.

    Why Aspect Ratios Matter

    Responsive Design

    CSS aspect-ratio property and padding-top tricks rely on knowing the correct ratio. Getting it wrong creates layout shift when images load at unexpected dimensions.

    Video Production

    YouTube needs 16:9, Instagram Reels need 9:16, and TikTok needs 9:16. Shooting in the wrong ratio means cropping out parts of your footage.

    Print & Photography

    Standard photo print sizes (6×4, 8×6) are 3:2. Cropping a 16:9 widescreen image for print loses significant content from the sides.

    Social Media

    Each platform has preferred ratios, 1:1 for Instagram grid, 4:5 for feed, 9:16 for stories. Using the right ratio maximises screen space in the feed.

    CSS Aspect Ratio

    Modern CSS has a native aspect-ratio property that enforces ratios without padding hacks:

    Modern approach

    img {
  aspect-ratio: 16 / 9;
  width: 100%;
  object-fit: cover;
}

    Legacy padding trick

    .wrapper {
  position: relative;
  padding-top: 56.25%; /* 9/16 */
}
.wrapper > img {
  position: absolute;
  inset: 0;
}

    The aspect-ratio property has 95%+ browser support. Use it for image containers, video embeds, and card layouts to prevent layout shift (CLS) while images load.

    Related Tools

    Image Resizer

    Resize images to exact dimensions

    Image Cropper

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    Screen Size Checker

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    Placeholder Image Generator

    Create sized placeholder images

    Image Compressor

    Reduce image file sizes

    Image to WebP

    Convert to WebP for smaller files

    How to use this tool

    1

    Enter the width and height of your image in pixels

    2

    Read the calculated aspect ratio, decimal ratio, and orientation

    3

    Use the ratio to resize proportionally or match a target format

    Common uses

    • Checking if an image fits a target format like 16:9 or 1:1
    • Calculating matching dimensions for proportional resizing
    • Verifying aspect ratios before cropping for social media
    • Finding the correct resize dimensions for print sizes

    Share this tool

    Frequently Asked Questions

    What is an aspect ratio?
    An aspect ratio is the proportional relationship between an image's width and height, expressed as W:H (e.g. 16:9). It tells you the shape of the image, not its size.
    What aspect ratio is 1920×1080?
    1920×1080 has an aspect ratio of 16:9, the standard for full HD video, most modern monitors, and YouTube videos.
    How do I resize without cropping?
    Enter your target width or height and the calculator will give you the matching dimension that preserves the original ratio. This prevents distortion.
    What's the difference between 16:9 and 4:3?
    16:9 is widescreen (used for modern TVs, YouTube, and most monitors). 4:3 is the older 'standard' ratio used for traditional TV, iPad screens, and some presentations.
    What aspect ratio should I use for Instagram?
    Instagram supports 1:1 (square), 4:5 (portrait, recommended for feed), and 1.91:1 (landscape). Stories use 9:16 (vertical full screen).
    What does 'aspect ratio' mean for printing?
    Print sizes have specific ratios. A 4×6 print is 3:2, an 8×10 is 4:5, and an 11×14 is roughly 7:9. Matching your crop to the print ratio avoids unexpected cropping at the print shop.
    Can I convert between aspect ratios without distortion?
    Not without cropping or adding borders (letterboxing/pillarboxing). Changing aspect ratio always means either cutting content or adding space.
    What aspect ratio is best for YouTube thumbnails?
    YouTube thumbnails use 16:9 at 1280×720 pixels. This matches the video player shape so your thumbnail fills the frame without black bars.
    How do I calculate aspect ratio manually?
    Divide width and height by their greatest common divisor. For 1920×1080: GCD is 120, so 1920÷120 = 16 and 1080÷120 = 9, giving 16:9.
    What aspect ratio do ultrawide monitors use?
    Most ultrawide monitors use 21:9 (2560×1080 or 3440×1440). Super ultrawide monitors use 32:9 (5120×1440), essentially two 16:9 screens side by side.
    Does aspect ratio affect image quality?
    No. Aspect ratio only describes the shape. Quality depends on resolution (total pixels), compression, and source. A 16:9 image can be low or high quality.
    What aspect ratio is used for cinema?
    Most modern cinema uses 2.39:1 (often called 'scope' or 'CinemaScope'). IMAX films use 1.43:1 or 1.90:1. The black bars you see on a TV are from the ratio mismatch.

    Results are for general informational purposes only and should be checked before use. They are not professional advice. See our Disclaimer and Terms of Service.