Hint: This is about a million times more accurate that that junky chart on the eliptical trainer.

Determine the rate at which you are going to do your cardio: 

First determine your Resting Heart Rate. 

This is most accurately accomplished by taking your pulse for 1 full minute first thing in the morning, before you even get out of bed. Double check it by taking a 15 sec pulse and then multiplying by 4. 

Now plug your RHR, or Resting Heart Rate, into this formula.  

220 – Age – RHR x % + RHR = Target Heart Rate 

So let