Sprout Social has a free tool that will save you time creating graphics for social media. With this tool, you can resize one image to fit all of the suggested dimensions for the most popular social networks, including Twitter, Facebook, Instagram, LinkedIn, Google+, Pinterest and YouTube. Of course, you have a custom option for those special images.

You can upload a jpg, png or gif format image. The Landscape app can generate many "post type" images from your uploaded image. Most of the time you will want to create an in-stream or post image for a social post. But, you also have the option to create a profile or cover image for each network.

Finally, you have the option to crop the generated image by zooming in and out on the image within the cropping window or dragging the image within the window. Once you have completed the process, just click the Next button to download the zip file containing all of the images that you requested. Below are the image post types available for each network.

Twitter
Profile Photo
Header Photo
In-Stream Tall
In-Stream Wide

Facebook
Profile Picture
Cover Photo
Linked Image
In-Stream Square

Instagram
Profile Picture
In-Stream Square
In-Stream Tall
In-Stream Wide

LinkedIn
Profile Photo
Header Image
Logo
Banner
In-Stream Wide
In-Stream Tall

Google+
Profile Photo
Cover Photo
In-Stream Tall
In-Stream Wide

Pinterest
Profile Picture
Pin Board
In-Stream Short
In-Stream Tall

YouTube
Channel Art
Channel Icon
Thumbnail

The Process

Upload the image that you wish to resize. You can drag the image from your files window or click the Upload link to manually select the image.

Now you have the option to choose one or more social networks. Or you can do it all in one step by clicking the link Have Landscape Auto-crop Instead. Let's try the one step option.

One Step Method

1. When you click the link, you will be taken to the next page and the download option window. Choose Save File and save the zip file to your computer.
   
   
2. Unzip the download file.
   
   When you unzip the zip file, you will get a folder containing all 29 images listed above. Each image's name indicates it purpose. For example, the facebook-Cover_Photo.jpg image is the cover photo for your Facebook page.
   
   

Multiple Networks Method

1. After uploading your image to the app, select which of the seven networks that you wish to use and click the Next button.
   
   On the next page, you will see all the Post Type image options for the first network that you have chosen.
   
   
2. Select the Post Types that you wish to generate for the first network and click Next.
   
   On the next few pages, you will repeat the process for each network that you have chosen.
   
   
3. On the next page, you have the option to crop the first of the generated images.
   
   On the next few pages, you will repeat the cropping process for all the images.
   
   When you have cropped all the images, you will download the zip file.
   
   
   

Sprout Social Landscape App
https://sproutsocial.com/landscape

Always Up-to-Date Guide to Social Media Image Sizes
https://sproutsocial.com/insights/social-media-image-sizes-guide/
https://docs.google.com/spreadsheets/d/1IpTYTTMJLcSXcPDtW9zSbPBHQyRdrLfKERohGIIkE_Q/edit#gid=476246499

Always Up-to-Date Guide to Social Media Video Specs
https://sproutsocial.com/insights/social-media-video-specs-guide/