Once you know your image DPI, do the following formula: Divide the pixel dimensions by the resolution
It's a safe bet to save images between 1500 px and 2500 px wide. Search for "Save for the web" or "Optimize for web" on your image editing software and use that feature.
We do optimize post images for the web and varying devices. If you are using our Image post option, the optimized version will populate in your post feed. When patrons click on the image, the image will expand to its original uploaded size.