Why you can’t subtract FIP from ERA

[SirKodiak]

by Colin Wyers
Okay, so the title is misleading. They're both numbers and can be subtracted from one another with wild abandon. Just don't expect it to mean anything.

http://www.hardballtimes.com/main/blog_article/why-you-cant-subtract-fip-from-era/

[SirKodiak]

Makes sense that FIP (or DICE) should not be subtracted from ERA. One is designed to look into the future and the other is a accounting of the past.