Aspect Ratio Calculator
Resize images and video without distortion
The Aspect Ratio Calculator finds the proportional relationship between width and height, and solves the missing dimension when you resize. Enter your original size and a target width (or height) — it returns the other dimension so your image or video scales without stretching or distortion.
It also simplifies the ratio to its cleanest form (1920×1080 → 16:9) and recognises common formats: widescreen 16:9, vertical 9:16 for Stories and TikTok, classic 4:3, square 1:1, cinematic 21:9, photographic 3:2, and laptop 16:10.
Formula
New height = new width × (original height ÷ original width)
New width = new height × (original width ÷ original height)
Designers working in CSS may also want our px to rem calculator for converting the resulting pixel values into relative units.
Example
You have a 1920×1080 video and need it 1280px wide.
Ratio: 1920 ÷ 1080 = 1.7778 (16:9). New height = 1280 ÷ 1.7778 = 720px.
So the resized video is 1280×720 — same shape, no distortion.
Frequently Asked Questions
What is an aspect ratio?
Aspect ratio is the proportional relationship between an image's width and height, written as width:height. A 16:9 image is 16 units wide for every 9 units tall — regardless of its actual pixel size. 1920×1080 and 1280×720 are both 16:9.
How do I calculate aspect ratio?
Divide both dimensions by their greatest common divisor. For 1920×1080 the GCD is 120, giving 16:9. Or simply divide width by height for the decimal form: 1920 ÷ 1080 = 1.78.
What is the aspect ratio of 1920x1080?
16:9 — the standard widescreen format used by YouTube, TVs, and most monitors. Other 16:9 resolutions include 1280×720 (720p), 2560×1440 (1440p), and 3840×2160 (4K UHD).
How do I resize an image without distorting it?
Keep the aspect ratio locked: if you change the width, multiply the new width by (original height ÷ original width) to get the correct new height. This calculator does it automatically — enter the original size and one new dimension.
What aspect ratio is Instagram?
Feed posts support 1:1 (square, 1080×1080), 4:5 portrait (1080×1350), and 1.91:1 landscape (1080×566). Stories and Reels are 9:16 (1080×1920). Since 2025 Instagram's grid preview crops toward 3:4, so keeping key content centred matters.
What aspect ratio is TikTok and YouTube Shorts?
Both use 9:16 vertical video, typically 1080×1920. Standard YouTube videos are 16:9 (1920×1080 or higher). Uploading 16:9 footage to a 9:16 platform results in either heavy cropping or letterboxing bars.
What is the aspect ratio for a 4K video?
Consumer 4K (UHD) is 3840×2160 — still 16:9, exactly four times the pixels of 1080p. Cinema 4K (DCI) is 4096×2160, a slightly wider ≈1.9:1 ratio used in film production.
What is a 16:10 aspect ratio used for?
Laptop displays. MacBooks and many premium Windows laptops use 16:10 (e.g. 2560×1600, 1920×1200) because the extra vertical space suits documents and code better than 16:9.
How do I calculate the height for a 16:9 image if I know the width?
Multiply width by 9/16 (= 0.5625). A 1200px-wide 16:9 image is 1200 × 0.5625 = 675px tall. For the reverse, multiply height by 16/9 (≈ 1.778).
What is the CSS aspect-ratio property?
Modern CSS lets you set aspect-ratio: 16 / 9 on an element and the browser computes the missing dimension automatically — no more percentage-padding hacks. It's supported in all current browsers and is ideal for responsive video embeds and image placeholders.
What aspect ratio are photos printed at?
Most DSLR and mirrorless photos are 3:2 (matching 35mm film), while phone cameras usually shoot 4:3. Standard print sizes differ — 4×6 inch is 3:2, but 5×7 and 8×10 are not, which is why prints often crop your photo edges.
What does letterboxing mean?
Letterboxing adds black bars above and below (or beside) a video when its aspect ratio doesn't match the screen — e.g. a 21:9 film on a 16:9 TV. It preserves the full image instead of cropping it. The alternative, cropping to fill, is called pan-and-scan.