How is stem length measured?

[howierart]

I need to put a shorter stem on my roadbike as my new one has far too much reach. However looking online I see the measurements are from 100mm to around 160mm. How is this normally measured for example for a standard ITM stem? I presume it is from the center of the head tube part to the centre of the handlbars - Am I right?

Thanks.

 

[serenaslu]

I need to put a shorter stem on my roadbike as my new one has far too much reach. However looking online I see the measurements are from 100mm to around 160mm. How is this normally measured for example for a standard ITM stem? I presume it is from the center of the head tube part to the centre of the handlbars - Am I right?

Thanks.

That is correct. See the following diagram for example:
http://www.lhthomson.com/docs/005_Elite_Stem.pdf

The following excel spreadsheet is also handy for quickly evaluating changes in reach and drop with stem length and rise angles for a given headtube angle:
http://www.hammerheadbikes.com/docs/stemcalculator.xls