5:05 on a treadmill

I'm still training to run a 5 minute mile, which is tough with snow and ice everywhere for the past several weeks. This morning, I ran a 5:05 mile on the treadmill at the gym, which is faster than I could run it outside, I'm sure, where I actually have to propel my body forward rather than just move my legs fast. Anybody know how to convert treadmill time to real time?