With so many social media platforms, how do you remember the various image size optimization guidelines?

A cool tip is to bookmark this blog post from websitehub and the related infographic to stay updated with any changes to the social media image size optimisation rules.

Twitter Image Sizing Tips
Profile Photo: 400 x 400 pixels (a maximum 100 KB file size)
It is often said that the “first impression is the last impression”!
Your Twitter profile picture is your main identification mark that will be visible to everyone. It will be visible on your home page, on the Twitter stream of your followers whenever you Tweet and so on.
Since it represents you or your brand, the image should be of the highest quality.

Header Photo: 1 500 x 500 pixels (a maximum 10 MB file size)

You can use an eye-catchy, creative image for your high-resolution header photo on your Twitter profile page. As a business, your Twitter page header photo should be in sync with your logo, tagline and brand.
In-stream Photo: 440 x 220 pixels (a maximum 5 MB file size for photos and 3 MB file size for animated gifs)

You can post up to four pictures along with your tweets on this platform. For every in-stream picture, an image link is created which takes up the Twitter character space. You simply need to maintain the 2:1 ratio of the images which can be reduced to a smaller version to effectively fit your follower’s stream.

Image Sizing Advice for Facebook
Cover Photo: 851 x 315 pixels (a preferred maximum file size of 100 KB)
You can edit and add creative images as your cover photo that represents you or your business in the correct sense. Try to maintain a minimum size of about 399 x 150 pixels.
Profile Picture: 180 x 180 pixels
Unlike the cover photo, which only appears on your Facebook page, your Facebook profile picture will be seen on your page, on posts where you comment, on the timelines of others where you post messages, in search results of Facebook’s Open Graph and so on.
In short, it represents you at most places on the largest social networking platform.
Shared Image: 1 200 x 630 pixels
You can engage your friends or business followers in meaningful conversations by sharing useful images on your Facebook timeline. These will appear in the news feeds of your friends and followers. Check this post for more information on image sizes for Facebook
Image Sizing Guidelines for Google+
Profile Image: 250 x 250 pixels
Again, this picture will be your identity across the Google+ network. Even though the dimensions are for a square image, your Google+ profile picture appears as a circle.
So, you need to take special care of how your image looks without the important parts being cut out.
Cover Picture: 1 080 x 608 pixels
You can use a large picture representing your brand, logo and business tagline as your Google+ cover image.
Shared Image: 497 x 373 pixels
You can share images on your Google+ posts and indicate the specific “circles” with whom you want to share the image and for whom it may be more relevant. Remember, such images (along with the associated text) are likely to turn up in the Google search engine for search queries related to your posts or business.
Instagram Image Sizing Rules
Profile Picture: 110 x 110 pixels
Photo Size: 640 x 640 pixels
Photo Thumbnails: 161 x 161 pixels
For all types of Instagram images, you need to maintain an aspect ratio of 1:1. So, all your images will appear in square dimensions. You need to take special care with the image quality because limited text content is shared on this platform. It is more about the pictures and visuals!
Recommended Image Sizes for Pinterest
Profile Picture: 165 x 165 pixels
A Pinterest profile picture may not be as important as that of Facebook or Twitter profile pictures. However, you still need to use a nice one. After all, anyone who arrives at your board or pins through the keyword search will probably have a look at your profile too.
Board Display Image: 222 x 150 pixels
Use eye-catchy images for posting on the relevant Pinterest boards.
Pin Sizes: a width of 236 pixels (with scaled height)
Though these are the dimensions for your Pinterest pins, expanded pins will have a minimum width of 600 pixels. You can post larger images (as only the width is fixed, while the length can be scaled further up) for better engagement and more re-pins or likes.
Optimisation Rules for Tumblr Image Sizes
Profile Image: 128 x 128 pixels
You can use a good looking square profile picture that visually represents you or your business on Tumblr. It will appear on your profile page, next to the button to “follow” you when someone lands on your page and as thumbnails next to your posts in your follower’s feeds.
Image Posts: 570 x 750 pixels
You can post images with up to 10 MB file sizes (except for animated gifs which should not be more than 1 MB). You can thus upload really high-quality pictures for your Tumblr posts.
YouTube Image Sizing Guidelines
Channel Cover Picture: 2560 x 1440 pixels (for desktop), 1855 x 423 pixels (for tablets), 1546 x 423 pixels (for smartphones), and 2560 x 1440 pixels (for TV)

The sizes are optimised for the different platforms as YouTube videos are often streamed using any of the above mentioned platforms. Also, the video channel cover image should tell your viewers more about the kind of videos that they will probably be able to view on your channel.

Video Uploads: 1 280 x 760 pixels

You know that YouTube is a video sharing site and not an image sharing one. So, you need to maintain this resolution (about 16:9 aspect ratio) for the videos that you upload.

Image Size Optimisation for LinkedIn
Standard Logo: 100 x 60 pixels
Career Cover Picture: 974 x 300 pixels
Banner Image: 646 x 220 pixels

For this professional social networking platform, you should make sure that all your images are embedded with text to add more contexts.

Also, make sure that you use creativity to showcase the most relevant things about your business and brand in the banner image as well as in your cover image.

It is bound to get you connected and engaged with more professionals. Even from a personal profile perspective, you can leverage the most out of this platform by having creative images to make professionals sit up and take notice.