1500 bytes is the MTU of IP, in most cases. It often excludes the Ethernet header, which is 14 bytes excluding the FCS, preamble, IFG, and any VLANs.

If have a 1500 byte MTU for IP, then we need at least a 1514 byte MTU for IP + Ethernet. We often call the > 1514B MTU the "interface MTU". It's unnecessarily confusing.