Aspect Ratio Calculator
Reduce a width and height to a simple aspect ratio like 16:9, or find the missing side for a target ratio, with 1920×1080 and 1280×720 examples.
Results
Ratio
- Width
- 1,920
- Height
- 1,080
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Educational estimates · not financial advice · free, no signup
Formula / how it works
Simplified ratio = width ÷ GCF : height ÷ GCF. Missing height = width × ratio height ÷ ratio width. Missing width = height × ratio width ÷ ratio height.
Detailed guide
What it is, how to use it, how to read the numbers, common mistakes, a worked example, formulas, and FAQs.
What this calculator is
Aspect ratio is the proportion between an image or screen's width and height. 1920×1080 pixels simplifies to 16:9, the standard for most video and monitors. Other common ratios are 4:3 for older screens, 3:2 for many cameras and 1:1 for square posts. This calculator works in three modes: it simplifies a width and height, finds the width for a given height and ratio, or finds the height for a given width and ratio. The results may be fractions of a pixel, so round to whole pixels, and choose dimensions that keep your ratio close enough for the format.
When to use / who it helps
- You are resizing an image or video without distorting it.
- You need dimensions for a social post or thumbnail.
- You are comparing screens.
- You are setting up a responsive layout.
- You are converting between 16:9 and 4:3.
How to use
Steps
- Choose the mode.
- To simplify, enter the width and height.
- To find a side, enter the known side and the ratio parts.
- Read the ratio or the missing dimension.
- Round to whole pixels.
- Check the new size by dividing width by height.
How to interpret results
- 16:9 equals about 1.778.
- 4:3 equals about 1.333.
- A ratio is the same for any scale of the same shape.
- Rounding can cause a one-pixel difference.
- Cropping changes the ratio; scaling does not.
Common mistakes & gotchas
- Entering width and height in the wrong order.
- Scaling one side only and distorting the image.
- Not rounding to whole pixels.
- Confusing 16:9 with 9:16.
- Forgetting that cropping changes the ratio.
Worked example
Worked example — 1920×1080, and finding sizes for 16:9 and 4:3
- The GCF of 1920 and 1080 is 120, so 1920×1080 simplifies to 16:9.
- Width for a 16:9 image 720 high: 720 × 16 ÷ 9 = 1,280.
- Height for a 4:3 image 1,280 wide: 1,280 × 3 ÷ 4 = 960.
- Check: 1,280 ÷ 720 = 1.778, the same as 16 ÷ 9.
Result: 1920×1080 is 16:9, and a 16:9 image 720 pixels high is 1,280 pixels wide.
To load the form's own demo values, tap Try example above the Calculate button.
How to calculate / formula
Simplified ratio = width ÷ GCF : height ÷ GCF. Missing height = width × ratio height ÷ ratio width. Missing width = height × ratio width ÷ ratio height.
Frequently asked questions
What is 1920×1080 as a ratio?
16:9.
How do I resize without distortion?
Scale both sides by the same factor.
What is 9:16?
The same as 16:9 but in portrait orientation.
What ratio are most cameras?
Often 3:2 or 4:3.
Why are my pixel results not whole numbers?
Not every ratio divides evenly; round to the nearest pixel.
Does cropping change the ratio?
Yes.