With the sole of the club flush with the floor, measure from the floor (heel side) up along the length of the club. There are two points where you could stop your measurement at the grip where this will give you the raw length or total length. Raw length is to the bottom side of the cap of the grip (or white line if there is no cap) and the total length is to the top of the cap on the grip. Usually this difference is like a 1/4 of an inch. I believe Titleist uses the raw length for their listed measurements and custom club orders

Titleist standard iron lengths are listed as 1/4" longer than miz, however, others posts I have read (not Titleist) have compared "off the shelf" miz and Titleist clubs and found them to be the same "finished" length which would indicate that Titleist length measurement must be to the top of the grip cap. This comparison was several years ago so the Titleist measuring method may have changed-hopefully Titleist will confirm how they actually do measure as it would be of interest (and assistance) to those coming to Titleist from other brands where they could take this information along with the lie differences to make an informed buying decision.

i have confirmed with both Titleist and miz that their website measurements are both before gripping, thus, Mr. Phine's comment on measuring with the grip on would be correct with the difference between raw and finished length being between 1/8 and 1/4 inch. Below are the responses from Titleist and miz:

The finished length of recent Titleist clubs would be the listed measurement plus the butt cap which varies by approximately 1/8-1/4". ie a 45" driver would be 45" plus the butt cap so anywhere between 45 1/8" to 45 1/4".

Thank you for contacting miz USA. All of our length measurements are done without the grip installed to ensure the most consistent and accurate measurements.