PicMonkey is a great online tool for sizing and optimizing your images. All you have to do is upload an image and PicMonkey helps with the rest.
1. Navigate to PicMonkey.com.
2. Click Edit a Photo.
3. Browse for the image file that you want to modify.
4. Click Open.
5. Use the tools on the menu to modify the image to your specifications.
6. When you're finished editing, click Save.
7. Choose quality settings for your picture and then click Save to my computer.