It is important to find the right home and loan to match your budget. Use our mortgage loan calculator to figure out your estimated monthly payment in advance by estimating your loan amount, interest rate, and length of mortgage.

This simple mortgage loan calculator calculates your monthly payment based on your input. Select the Taxes and Insurance box to estimate your impounds (taxes, insurance, mortgage insurance). This calculator assumes conventional mortgage financing for calculating mortgage insurance.

Mortgage Calculations by Hand (from their web site)

The following assumes a typical conventional loan where the interest is compounded monthly. First we'll define two more variables to make the calculations easier: J = monthly interest in decimal form = I / (12 x 100) N = number of months over which loan is amortized = L x 12

Now for the big monthly payment (M) formula ... it is:

 	                    J
         M  =  P  x ------------------------
                 
                      1  - ( 1 + J ) ^ -N

where 1 is the number one (it does not appear too clearly on some browsers)
So to calculate it, you would first calculate 1 + J then take that to the -N (minus N) power, subtract that from the number 1. Now take the inverse of that (if you have a 1/X button on your calculator push that). Then multiply the result times J and then times P.

The one-liner for a program would be (adjust for your favorite language):

M = P * ( J / (1 - (1 + J) ** -N))

So now you should be able to calculate the monthly payment, M. To calculate the amortization table you need to do some iteration (i.e. a simple loop). Here are the simple steps :

Step 1: Calculate H = P x J, this is your current monthly interest Step 2: Calculate C = M - H, this is your monthly payment minus your monthly interest, so it is the amount of principal you pay for that month Step 3: Calculate Q = P - C, this is the new balance of your principal of your loan. Step 4: Set P equal to Q and go back to Step 1: You thusly loop around until the value Q (and hence P) goes to zero.

Many people have asked how to find N (number of payments) given the payment, interest and loan amount. The answer to the actual formula is in the book: The Vest Pocket Real Estate Advisor by Martin Miles (Prentice Hall). Here's the formula:

n = -1/q * (LN(1-(B/m)*(r/q)))/LN(1+(r/q))

• q = amount of annual payment periods
• r = interest rate
• B = principle
• m = payment amount
• n = amount payment periods
• LN = natural logarithm