How well does a football helmet protect against impact?

Can't tell if you've accidentally placed this question in the wrong category, or if you want to use a motorcycle helmet for bike riding.

But basically any helmet is better than no helmet, but a helmet built for the intended usage is better than just using any helmet.

In this case a football helmet is designed to be able to take several hits with lesser energy than compared to a motorcycle helmet.

An MC helmet is expected to protect against one massive hit and then to be discarded.