Working on images is a hassle. And if you are a photographer, you might know tricks in Photoshop to resize multiple images.
This guide DOES NOT use photoshop or any imaging tool.
1] Visit bricelam.net/ImageResizer and download the Image Resizer.
It is a very small tool which helps to resize the images simultaneously.
2] After installing select many images as you like, Right Click on them and select “Resize Pictures”.
3] Select the resolutions/sizes you want the images in. Then refresh the window and the resized images will appear. (Converting depends on your processor speed)