📐 Aspect Ratio Calculator
Calculate and lock aspect ratios, preview dimensions visually, compute PPI, and scale resolutions.
Last updated: May 18, 2026 · By Λ
⚖ Ratio Calculator
🎚 Preset Ratios
💻 Common Resolutions
👁 Visual Preview
📏 Scale Calculator
Enter current dimensions above, then set a target width or height to get the scaled result.
🔎 Pixel Density (PPI / DPI)
Uses the width and height entered above plus the diagonal screen size to compute PPI.
Free Aspect Ratio Calculator
Calculate the simplified aspect ratio from any pixel dimensions, lock the ratio and auto-fill the other dimension, pick from common presets, preview the shape visually, compute pixel density (PPI/DPI), and scale dimensions proportionally. Every calculation, from the GCD simplification to the PPI math, executes as JavaScript inside this page, so the dimensions you type stay on your machine.
What is an Aspect Ratio Calculator?
An aspect ratio describes the proportional relationship between the width and height of an image, video, or screen. It is typically expressed as two numbers separated by a colon, such as 16:9 or 4:3. Understanding aspect ratios is essential for photographers, videographers, graphic designers, web developers, and anyone working with visual media. Getting the ratio wrong can lead to stretched, cropped, or distorted content that looks unprofessional.
This free online aspect ratio calculator simplifies the process of finding, locking, and scaling ratios. Instead of doing the math manually, you enter your dimensions and instantly see the simplified ratio. You can lock a ratio and have the calculator automatically compute the matching width or height as you change one dimension. The tool also includes preset ratios for common standards (16:9, 4:3, 21:9), popular resolution presets (Full HD, 4K, 8K), a visual preview, a scale calculator, and a pixel density (PPI) calculator. Once loaded, the page needs no server round trips at all, and none of your numbers are transmitted.
How to Use This Tool
- Enter a width and height in pixels in the Ratio Calculator section. The simplified aspect ratio appears automatically below the inputs.
- Check "Lock ratio" to constrain the proportions. When locked, changing one dimension will automatically update the other to maintain the same ratio.
- Use the Preset Ratios or Common Resolutions buttons to quickly load standard dimensions like 1920x1080 (Full HD) or 3840x2160 (4K UHD).
- Use the Scale Calculator to resize proportionally by entering a target width or height. Use the PPI calculator by entering a diagonal screen size in inches to compute pixel density.
Key Features
- Automatic Ratio Simplification - Enter any pixel dimensions and the tool calculates the greatest common divisor to display the simplest ratio (for example, 1920x1080 becomes 16:9).
- Ratio Locking - Lock the current ratio so that changing one dimension automatically updates the other, ensuring your proportions stay consistent.
- Visual Preview - A proportional rectangle updates in real time to give you a visual sense of the shape your dimensions produce.
- Scale Calculator - Enter a target width or height and get the proportionally scaled counterpart, along with the scaling percentage.
- PPI/DPI Calculator - Enter your screen's diagonal size in inches to calculate pixel density, total diagonal pixels, and physical screen dimensions.
Frequently Asked Questions
What is the most common aspect ratio for video?
The 16:9 aspect ratio is the most widely used for video content. It is the standard for HD, Full HD (1920x1080), QHD (2560x1440), and 4K UHD (3840x2160) resolutions. Most YouTube videos, streaming platforms, and modern televisions use 16:9 as well.
What aspect ratio should I use for social media?
It depends on the platform. Instagram feed posts commonly use 1:1 (square) or 4:5 (portrait). Instagram Stories and TikTok use 9:16 (vertical). Twitter and Facebook cover images typically use 16:9. LinkedIn banner images use approximately 4:1. Check each platform's current guidelines for the best results.
What is PPI and why does it matter?
PPI stands for Pixels Per Inch and measures how many pixels are packed into each inch of a screen. A higher PPI means sharper, more detailed images. It is especially important when designing for print (where 300 PPI is standard), for retina/HiDPI displays, or when comparing screen quality across different monitor sizes.
How do I resize an image without distortion?
To resize without distortion, you must maintain the original aspect ratio. Enter your current dimensions in this calculator, lock the ratio, then enter the new width or height you need. The tool will compute the correct corresponding dimension so your image scales proportionally without stretching or squishing.