How this calculator works
Integer dimensions are simplified with their greatest common divisor. Resizing keeps the width-to-height ratio constant and may produce a fractional pixel dimension. A real image editor may round that dimension, slightly changing the exact ratio. This calculator does not crop or resample images.
The formula
Ratio = (width / GCD) : (height / GCD)
New height = new width × original height / original width
New width = new height × original width / original height.A quick example
1920 × 1080 simplifies to 16:9. Setting the new width to 1280 gives height 720; setting height to 900 gives width 1600.
How to use this calculator
- Enter positive whole-pixel original dimensions.
- Choose ratio only, resize by width or resize by height.
- Calculate proportional dimensions and account for pixel rounding if needed.
A few common questions
Can the resized result contain a fraction?
Yes. Exact proportional resizing does not always land on a whole pixel.
Does this crop to a different ratio?
No. It preserves the original proportions.
Can width or height be zero?
No. Both must be positive for a defined image aspect ratio.