Any particular version of IE acting up or is it all of them?
How about a reduced case example? That might help you see if other CSS in your page is creating the problem or if it specifically is calc. If you do that in CodePen and post it here, it would be really helpful for us to help you troubleshoot, otherwise we’re just guessing.
If your tests indicate that other CSS is impacting on calc, a link to your actual page would be great too.