Weighing your debt basically consists of figuring out what the average rate is you are paying.  This works great if you have a primary mortgage plus a HELOC (Home Equity Line of Credit) or a secondary mortgage. 

The first step is to add up your debt.  For example, you have a $200,000 primary mortgage at 5.875% and a HELOC with a balance of $100,000 with a rate of 7.25%.  Your total debt is $300,000.

The next step is to divide your primary mortgage of $200,000 by your total debt of $300,000.  This will produce .67, which you will then multiply by your primary mortgage rate of 5.875% which equals 3.94%.

The third step is to do the same process with your HELOC.  Divide $100,000 by $300,000 which will produce .33.  Multiply .33 by 7.25 and you get 2.39%.

Now, you will add  2.39 plus 3.94 and you get 6.33.  So, you are paying an average of 6.33% on both mortgages.