Medium rare: 130-135° (remove from heat at 125° )
Medium: 135-145° (remove from heat at 130° )
Medium well: 145-155°. (remove from heat at 140° )
Note: The reason you take steaks off the heat BEFORE the desired finish temperature is because they will continue to cook (with temperature rising 7° on average) as they rest for 10 minutes before cutting.