Work out aspect ratio resize instantly with clear inputs, formula shown and shareable results.
Keeping the aspect ratio means the new height is the new width divided by the original width over height ratio. Pixel count changes with the square of the scale factor, so scaling to two thirds the width leaves only 44% of the original pixels.
New height
new height = new width x original height / original width
Pixel change
pixels scale with the square of the linear scale factor
new height = new width x original height / original width. Keeping the aspect ratio means the new height is the new width divided by the original width over height ratio.
Pixel count changes with the square of the scale factor, so scaling to two thirds the width leaves only 44% of the original pixels.
Enter original width, original height, new width. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.