A calculator to resize whilst maintaining the same proportions.
A classic proportion wheel (aka proportion scale) is used by graphic designers to resize an image to fit within a target width (or height).
The general idea is to translate a given width/height so the image doesn't get distorted, thereby maintaining the same aspect ratio.
Enter the source dimensions in the blue fields and then enter the target size into the pink areas.
Modify any field to automatically calculate the other fields as you type.
Use the "closest whole number" button to find the next available size that has integers for both the width and height.
If you have an image that is 1000x600 and you want to fit it inside 700x300, you'll have to do some serious noodling wouldn't you?
For this scenario, simply enter 1000x600 into the blue fields, then choose which dimension is more important, width or height and enter either 700 into the pink width field or 300 into the pink height field.