When determining my yearly loans, I usually assume a 10% increase in tuition with a 5% increase in living expenses, and a flat 7.9% interest rate for loans. I know that these could be on the high side for many schools, but these can also be low for others. All said and done, I use this to try and predict what my loans will be in X year.
Here is an example if you would like:
First, lets just look at the face value of our loans:
$50,000 tuition and fees, $20,000 living = $70,000 per year. $70,000*4 years = $280,000 in loans
Now lets add price increases:
D1: $50,000 tuition and fees, $20,000 living = $70,000 loan
D2: $50,000*1.10 = $55,000 tuition and fees, $20,000*1.05 = $21,000 living = $76,000 loan
D3: $55,000*1.10 = $60,500 tuition and fees, $21,000*1.05 = $22,050 living, = $82,550 loan
D4: $60,500*1.10 = $66,550 tuition and fees, $22,050*1.05 = $23,153living, = $89,703 loan
Total loans before interest: $318,253 in loans
Now lets add a 7.9% interest. (remember not all of those loans will be at 7.9%, so these estimates are high):
D1: $70,000*(1+7.9%)^4 = $94,882
D2: $76,000*(1+7.9%)^3 = $95,472
D3: $82,550*(1+7.9%)^2 = $96,108
D4: $89,703*(1+7.9%)^1 = $96,789
Total debt on the day of graduation: $383,252 in loans
hope this helps