Another method I used is **Guides**. 



 1. Enable **Guides**. This option is found under View -> Guides -> Show guides 

(<kbd>Ctrl</kbd> + <kbd>Alt</kbd> + <kbd>E</kbd> <kbd>Ctrl</kbd> +
    <kbd>Alt</kbd> + <kbd>G</kbd>)

 2. Show Ruler. This option is found under View -> Show Ruler

 3. Drag two horizontal guides and two vertical guides. Measure out their spacing on the ruler

 4. Resize image according to the guides