LILLIAN WONG LOANS

Calculators​

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• Additional payment calculator
  How much do you save by paying more or making additional payments than your initial mortgage terms?

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• Monthly payment calculator
  Want to know how much your monthly payment is for your mortgage?

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• How much do I have to earn?
  Not sure how much money you'll have to earn to afford your house payment and accompanying expenses?

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• How much can I borrow?
  Want to know how big of a mortgage you can take on?

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• Should I pay discount points?
  Not sure if you should pay discount points on your mortgage loan?

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• How much will I save by refinancing my loan?
  How long will it take to recoup the costs of refinancing my home mortgage?

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• How much will my tax deduction be?
  Want to know how much your home mortgage will save you in taxes?

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• Bi-weekly mortgage calculator
  Want to know how much time and money you'll save paying off your loan on a bi-weekly payment plan?

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• APR calculator
  To find out the annual percentage rate of your loan, enter the loan amount, interest rate, points, other costs and year-length term.

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• Interest only monthly payment calculator
  To find out the monthly savings you could gain from an interest-only payment plan.

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• Mortgage Calculations by Hand
  Learn the formulas for calculating interest rates and payments.

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Mortgage Calculations by Hand

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First you must define some variables to make it easier to set up: P = principal, the initial amount of the loan I = the annual interest rate (from 1 to 100%) L = length, the length (in years) of the loan, or at least the length over which the loan is amortized.

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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 iterations (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))

 

Where:

• Q = amount of annual payment periods

• R = interest rate

• B = principle

• M = payment amount

• N = amount payment period

• LN = natural logarithm

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