Calculating Monthly Interest payment?

[Andy Thoman]

How can i figure out how much of my payments are going towards interest and principal?

I found an online calculator for finding my monthly payments, but how do I know how much each month is for interest?

For example, for simplicity sake if I had a loan for 100k at the interest rate of 5% over 30 years. My calculation says the monthly payment will be 536.82. How do I know how much of that is interest and principal? Is it just even each month? 

Over 30 years it would be total cost of $193,255.78. So the total amount of interest paid was $93,255.78. Are my assumptions correct on that on how the interest is paid?

However, I understand that earlier you are mostly paying interest. So how do I know for each month is interest and how much is principal?