Aspect Ratio Calculator — Resize & Scale

Free aspect ratio calculator. Calculate, convert, and scale aspect ratios for video, images, and screens. Find width or height from any ratio like 16:9, 4:3, 21:9.

Common Aspect Ratios

Aspect Ratio Calculator

Common Resolutions & Aspect Ratios

Name Resolution Ratio
SD (480p) 640 × 480 4:3
HD (720p) 1280 × 720 16:9
Full HD (1080p) 1920 × 1080 16:9
QHD (1440p) 2560 × 1440 16:9
4K UHD 3840 × 2160 16:9
8K UHD 7680 × 4320 16:9
Instagram Post 1080 × 1080 1:1
Instagram Portrait 1080 × 1350 4:5
Instagram Story/Reel 1080 × 1920 9:16
YouTube Thumbnail 1280 × 720 16:9
Facebook Cover 820 × 312 2.63:1
Twitter Header 1500 × 500 3:1
Ultrawide Monitor 3440 × 1440 21:9
iPad (standard) 2048 × 1536 4:3
iPhone 15 Pro 1179 × 2556 ~9:19.5

How to Use

Click a preset (16:9, 4:3, etc.) or enter custom width and height values.

Choose a mode: Find Ratio (from dimensions), Scale by Width (enter new width), or Scale by Height (enter new height).

Click Calculate to see the aspect ratio, visual preview, and scaled dimensions. Use the resolution table below for reference.

What is an Aspect Ratio?

An aspect ratio is the proportional relationship between the width and height of an image, video, or screen, expressed as W:H (e.g. 16:9). The most common aspect ratios are 16:9 (widescreen), 4:3 (classic), 1:1 (square), 9:16 (vertical/mobile), and 21:9 (ultrawide). To calculate it, divide both dimensions by their Greatest Common Divisor (GCD).

Complete Guide to Aspect Ratios

How to Calculate Aspect Ratio

To find the aspect ratio of any image, video, or screen, divide both the width and height by their Greatest Common Divisor (GCD). The GCD is the largest number that divides both values evenly.

Example: A 1920×1080 image. GCD of 1920 and 1080 is 120. Divide both: 1920÷120 = 16, 1080÷120 = 9. The aspect ratio is 16:9.

You can also express aspect ratios as decimals by dividing width by height: 1920÷1080 = 1.778. This is useful when comparing non-standard ratios.

Common Aspect Ratios Explained

16:9 (1.78:1): The universal widescreen standard. Used for HD/4K TVs, computer monitors, YouTube videos, Netflix, and most modern content. Resolutions: 1280×720 (720p), 1920×1080 (1080p), 3840×2160 (4K).

4:3 (1.33:1): The classic TV and early computer standard. Still used for iPads, some presentations, and retro aesthetics. Resolutions: 1024×768, 1600×1200, 2048×1536.

1:1: A perfect square. Standard for Instagram feed posts, profile pictures, album covers, and social media avatars. Common resolution: 1080×1080.

9:16: Vertical (portrait) orientation. The standard for TikTok videos, Instagram Stories/Reels, YouTube Shorts, and Snapchat. Essentially 16:9 rotated. Resolution: 1080×1920.

21:9 (2.33:1): Ultrawide format used for cinema films, ultrawide monitors, and immersive gaming. Resolutions: 2560×1080, 3440×1440.

4:5 (0.8:1): Instagram's recommended portrait format for feed posts — gives more vertical space and visibility in the feed compared to square. Resolution: 1080×1350.

How to Resize Without Distortion

When you resize an image or video, maintaining the aspect ratio prevents stretching or squishing. The formula is simple: new height = new width × (original height ÷ original width). For example, resizing a 1920×1080 image to 1280 width: 1280 × (1080÷1920) = 1280 × 0.5625 = 720. So the new dimensions are 1280×720 — same 16:9 ratio, no distortion. Our "Scale by Width" and "Scale by Height" modes automate this.

Aspect Ratios for Social Media

YouTube: 16:9 for videos (1920×1080 recommended). 9:16 for Shorts. Thumbnails: 1280×720.

Instagram: 1:1 (1080×1080) for feed. 4:5 (1080×1350) for maximum feed presence. 9:16 (1080×1920) for Stories and Reels.

TikTok: 9:16 (1080×1920). Full-screen vertical video is the only format that performs well.

Facebook: 1.91:1 (1200×628) for link previews. 4:5 for feed videos. 9:16 for Stories.

Twitter/X: 16:9 (1200×675) for in-stream images. 2:1 (1500×750) recommended for large cards. Header: 3:1 (1500×500).

Aspect Ratio vs Resolution — What's the Difference?

Aspect ratio describes the shape (proportional relationship of width to height). Resolution describes the size (actual number of pixels). Multiple resolutions can share the same aspect ratio: 1280×720, 1920×1080, 2560×1440, and 3840×2160 are all 16:9, but range from HD to 4K quality. When someone says "16:9" they mean the shape; when they say "1080p" they mean the resolution (1920×1080 pixels).

Aspect Ratios in Video Editing

When editing video, set your project aspect ratio before you start editing. Mixing footage with different ratios causes letterboxing (black bars) or cropping. If you shoot in 16:9 but deliver in 9:16 (for TikTok), you'll lose 75% of the frame. Many editors shoot in 4K 16:9 and crop to 9:16 in post-production, giving them flexibility to reframe for both horizontal and vertical delivery.

Frequently Asked Questions

What is an aspect ratio?
An aspect ratio is the proportional relationship between the width and height of an image, video, or screen. It is expressed as two numbers separated by a colon, like 16:9. The first number is the width and the second is the height. A 16:9 ratio means for every 16 units of width, there are 9 units of height.
What is the most common aspect ratio?
16:9 (widescreen) is the most common aspect ratio used for TVs, monitors, YouTube videos, and most modern content. Other common ratios include 4:3 (older TVs and iPad), 1:1 (Instagram posts), 9:16 (TikTok, Instagram Reels, phone screens vertical), and 21:9 (ultrawide monitors and cinema).
How do I calculate aspect ratio?
To calculate the aspect ratio from width and height: find the Greatest Common Divisor (GCD) of both numbers, then divide both by the GCD. For example, 1920×1080: GCD is 120, so 1920÷120 = 16 and 1080÷120 = 9, giving a 16:9 ratio. Our calculator does this instantly.
How do I resize an image while keeping the aspect ratio?
Enter the original width and height to find the aspect ratio. Then enter either a new width or new height, and the calculator will compute the other dimension to maintain the same ratio. This prevents your image from being stretched or squished.
What aspect ratio is 1920x1080?
1920×1080 is a 16:9 aspect ratio. This is Full HD (1080p) resolution and is the most widely used resolution for monitors, TVs, and video content.
What aspect ratio is 1080x1080?
1080×1080 is a 1:1 (square) aspect ratio. This is the standard format for Instagram posts, profile pictures, and album cover art.
What is 4:3 aspect ratio used for?
4:3 was the standard TV and monitor ratio before widescreen. It is still used for iPad screens, some presentations (like older PowerPoint templates), classic photographs, and retro-style content. Common 4:3 resolutions include 1024×768, 1600×1200, and 2048×1536.
What aspect ratio should I use for YouTube?
YouTube recommends 16:9 for standard videos. Common resolutions are 1920×1080 (1080p), 2560×1440 (1440p), and 3840×2160 (4K). YouTube Shorts use 9:16 (1080×1920). Square 1:1 also works but will have black bars on desktop.
What is the aspect ratio for Instagram?
Instagram supports multiple ratios: 1:1 (1080×1080) for feed posts, 4:5 (1080×1350) for portrait feed posts (most real estate on feed), 9:16 (1080×1920) for Stories and Reels, and 1.91:1 (1080×566) for landscape posts.
What is the difference between aspect ratio and resolution?
Aspect ratio is the proportion between width and height (like 16:9). Resolution is the actual number of pixels (like 1920×1080). Multiple resolutions can share the same aspect ratio — 1280×720, 1920×1080, and 3840×2160 are all 16:9 but at different quality levels.

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