Aspect Ratio Calculator
Fill in either Width or Height (leave the other blank) along with the ratio — the missing dimension is calculated automatically. If both are filled, the height will be recalculated to match the ratio.
Common Resolutions & Ratios (click a row to load it)
| Name | Resolution | Ratio |
|---|
How to Use
- Choose a mode: "Calculate Dimension" or "Find Ratio".
- Calculate Dimension: enter a known width or height and a target aspect ratio (e.g. 16:9) to find the missing dimension.
- Find Ratio: enter a width and height to see the simplified aspect ratio (e.g. 1920×1080 → 16:9).
- Use the common resolutions table for quick reference — click any row to load those dimensions into the calculator.
- Results update instantly as you type — no need to click Calculate.
Frequently Asked Questions
QWhat is an aspect ratio?
An aspect ratio describes the proportional relationship between an image or screen's width and height, written as width:height (e.g. 16:9 or 4:3). It stays the same regardless of the actual pixel size, as long as the image is scaled proportionally.
QHow do I resize an image while keeping its aspect ratio?
Divide the new width by the original width to get a scale factor, then multiply the original height by that same factor (or vice versa). This calculator does that automatically — enter your target width or height and the original ratio.
QHow is the simplified ratio calculated?
The width and height are divided by their greatest common divisor (GCD), reducing them to the smallest whole numbers that preserve the same proportion — e.g. 1920×1080 simplifies to 16:9.
QWhat are the most common aspect ratios?
16:9 is the standard for HD and 4K video and most modern monitors and TVs. 4:3 was the standard for older TVs and monitors. 21:9 is used for ultrawide monitors, and 9:16 is common for vertical phone video.
QDoes this tool resize actual image files?
No — this is a calculator only. It computes the dimensions you would need; you would then use image editing software to actually resize a file to those dimensions.
About This Calculator
Aspect ratio simplification uses the Euclidean algorithm to find the greatest common divisor (GCD) of the width and height. Dimension calculations use simple cross-multiplication to preserve the target ratio.
