Aspect Ratio Calculator

What is Aspect Ratio Calculator?

Aspect Ratio Calculator computes missing dimensions when scaling images and videos while preserving their aspect ratio. Enter width and height to see the ratio in simplified form (e.g., 16:9, 4:3, 1:1), or enter the ratio and one dimension to calculate the other. It also converts between common aspect ratios and helps fit content into target dimensions with letterboxing or cropping.

Aspect ratio is the proportional relationship between width and height. A 1920×1080 image has a 16:9 aspect ratio (1920/1080 = 1.777... = 16/9). Maintaining the correct aspect ratio when resizing prevents distortion — a circle stretched to 4:3 becomes an oval. Common ratios: 16:9 (HD video, YouTube, most monitors), 4:3 (older TVs, iPads), 1:1 (Instagram square, profile photos), 21:9 (ultrawide monitors), 9:16 (vertical video, Instagram Stories).

Practical applications: resizing images for web without distortion, calculating banner dimensions for advertising networks, finding crop dimensions that fit a target frame, planning video exports for different platforms (16:9 for YouTube, 9:16 for TikTok/Reels, 1:1 for Instagram), and calculating font sizes that scale proportionally with container dimensions.

How to Use

Enter the original width and height to see the simplified aspect ratio.
To scale to a new size, enter the original ratio and the known new dimension (width or height).
Use the 'Lock' button to fix one dimension and calculate the other when dragging a slider.
Select a preset ratio (16:9, 4:3, 1:1, 21:9) to quickly enter a target ratio.
Use the 'Letterbox / Pillarbox' calculator to fit your content into a target frame with padding.

Examples

Scale 1920×1080 to 1280 width

Result: 1920:1080 = 16:9 / New height = 1280 × (1080/1920) = 720 → 1280×720

What height for a 4:3 image at 800px wide?

Result: 800 × (3/4) = 600 → 800×600

Fit 16:9 video in a 4:3 frame

Result: Letterbox: add 75px black bars top and bottom (height = 4/3 × width, content height = 9/16 × width)

Frequently Asked Questions

What is the difference between 16:9 and 16:10?

16:9 (1.777:1) is the standard HD and Full HD ratio used by TVs, YouTube, and most monitors. 16:10 (1.6:1) is slightly taller and was common in professional and MacBook displays — it provides more vertical space for documents and code. 16:10 monitors at 1920×1200 vs 16:9 at 1920×1080 give 120 extra rows of pixels.

What is letterboxing and pillarboxing?

Letterboxing adds horizontal black bars at the top and bottom when wide content (16:9) is displayed in a narrow frame (4:3). Pillarboxing adds vertical black bars on the sides when tall content (4:3) is displayed in a wide frame (16:9). The alternative to bars is cropping (losing content) or stretching (distortion).

Why does social media crop my images?

Each platform uses a different display ratio for feed thumbnails. Instagram feed uses 4:5 (portrait) or 1:1 (square) for single images. Twitter shows 16:9 previews. Facebook link previews prefer 1.91:1. If your image doesn't match the platform's display ratio, it is center-cropped. Design content to the platform's preferred ratio or ensure your subject is centered.

What is the golden ratio and is it the same as aspect ratio?

The golden ratio (φ ≈ 1.618:1) is a mathematical ratio found in art, architecture, and nature. It is close to but not the same as 16:9 (1.778:1) or 3:2 (1.5:1). The golden ratio is used in graphic design composition and logo design. Some camera sensors use 3:2, which is close to but not the golden ratio.

What aspect ratio should I use for my website hero image?

Desktop hero images typically use 16:9 (landscape). Mobile hero sections often use 9:16 or 4:5 (portrait) or a square 1:1 crop. A common approach is to serve different crops for different breakpoints using the HTML element with multiple source elements. Alternatively, use a 2:1 or 21:9 ratio that works well on wide screens while not appearing too short on mobile.