Instagram photo sizes: 1080 x 1080 (square), 1080 x 566 (landscape), 1080 x 1350 (portrait)
Twitter profile picture size: 150 x 150
Twitter header size: 1500 x 500
Twitter post image size: 1024 x 512
LinkedIn company logo size: 300 x 300
LinkedIn cover photo size: 1536 x 768
LinkedIn profile picture size: 400 x 400
LinkedIn background photo size: 1584 x 396
LinkedIn post image size: 1200 x 1200 (desktop) 1200 x 628 (mobile)
Twitter header image size: 1500 by 500 pixels
Instagram ads sizes:
Landscape: 1080 by 566 pixels
Square: 1080 by 1080 pixels
Cheers,
Charlie and Ashleigh