PHP Mortgage Calculator

Sale Price, Length of Mortgage and Annual Interest Rate'); } if ($assessed_value <= 0 && $sale_price > 0) { $assessed_value = $sale_price * .85; } /* --------------------------------------------------------------------- */ /* KEY CALCULATIONS /* --------------------------------------------------------------------- */ // financing & down payment numbers $down_payment = $sale_price * ($down_percent / 100); $financing_price = $sale_price - $down_payment; // interest rates $annual_interest_rate = $mortgage_interest_percent / 100; $monthly_interest_rate = $annual_interest_rate / 12; // Principal & Interest monthly payment: financing & interest numbers from above as well as $year_term (length of mortgage, entered by user) $monthly_payment = $financing_price / _get_interest_factor($year_term, $monthly_interest_rate); // taxes $property_yearly_tax = ($assessed_value / 1000) * $property_tax_rate; $property_monthly_tax = $property_yearly_tax / 12; // PMI, if necessary if ($down_percent < 20) { $pmi_per_month = 55 * ($financing_price / 100000); } // Total principal, interest, pmi, taxes, fees $total_monthly_bill = $monthly_payment + $pmi_per_month + $property_monthly_tax + $condo_fee; /* --------------------------------------------------------------------- */ } catch (IncompleteException $e) { $form_complete = false; } catch (Exception $e) { $form_complete = false; echo '

' . $e->getMessage() . '

'; } ?>

Purchase & Financing Information

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Your total monthly payment is [Details]

Sale Price of Home:	(dollars)
Percentage Down:	%
Mortgage Interest Rate:	%
Length of Mortgage:	years
Assessed Home Value:	(dollars) The assessed value is used to compute property taxes. On average, properties are assessed at about 85% of their selling price. If you know the actual assessed value for this property, enter it here. If not, leave zero and we'll use 85% of the sale price.
Property Tax Rate:	(dollars per $1000) Property tax rates vary between states and towns. The US average is about $13.80 for every $1000 of the assessed home value.
Condo/Monthly Fee(s):	(dollars)
Explain Calculations:	/> Show the calculations and amortization

Mortgage Payment Information

Down Payment:
Amount Financed:
Monthly Payment:	(Principal & Interest ONLY)
Since you put less than 20% down, you will pay Private Mortgage Insurance. PMI tends to be about $55 per month for every $100,000 financed (until you have paid off 20% of your loan). This adds to your monthly payment.
Your property tax rate is per $1000. Your home's assessed value is . This means that your yearly property taxes will be , or per month.

Your Total Monthly Payment

Mortgage (Principal & Interest)
PMI
Property Tax
Condo Fee
Total Monthly Payment

Calculations

To figure out the monthly payment, we need to know (1) how much you're financing; (2) your monthly interest rate; and (3) how many months you're financing for.

Financials are typically quoted in yearly or annual numbers—a 30-year mortgage or a 6% annual interest. However, you pay your mortgage every month. A lot of the calculations involve translating those yearly numbers to their monthly equivalents.

1. Financing Price

First, we need to figure how much you're financing.

We can do this based on the sale price of the home () and the percent that you put down (%).

Start by calculating the down payment. Divide the percentage down by 100, then multiply by the sale price of the home.

(% / 100) x = , your down payment

Now we can calculate how much you're financing—how much you need to borrow. That's just the sale price minus your down payment.

- = , your financing price

2. Monthly Interest Rate

That % interest rate percentage you secured is an annual percent.

We'll need to convert that from a percentage to a decimal rate, and from an annual representation to a monthly one.

First, let's convert it to a decimal, by dividing the percent by 100.

% / 100 = , the annual interest rate

Now convert the annual rate to a monthly rate by dividing by 12 (for 12 months in a year).

/ 12 = , your monthly interest rate

3. Month Term

Now for an easy calculation—the month term. That's just the number of months you'll be paying off your loan.

You have a year mortgage x 12 months = months, your month term.

Final: Your Monthly Mortgage Payment

Using the three numbers above, we can now calculate your monthly payment.

(financing price) x (monthly interest rate / (1 - ((1+monthly interest rate)^{-(monthly term)})))

x ( / (1 - ((1 + )^-()))) = , your monthly payment*

*Principal & Interest only. See total monthly payment for a your mortgage plus taxes, insurance, and fees. See amortization for a breakdown of how each monthly payment is split between the bank's interest and paying off the loan principal.

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Amortization

Amortization for monthly payment, , over years. Mortgage amortization only includes your monthly principal and interest payments. Property taxes, PMI, and condo fees are ignored when amortizing your mortgage.


Year Summary: You spent went to principal This is equity that your building up went to interest This is typically tax deductible
Principal & interest costs for the full years of this mortgage total…

This mortgage calculator can be used to figure out monthly payments of a home mortgage loan. This calculator automatically factors in PMI for loans where less than 20% is put as a down payment. Also taken into consideration are the town property taxes based on the mortgaged property's assessed valued.

The code for PHP Mortgage Calculator is free and can probably be downloaded from http://davetufts.com