Loan Input - Touch an input box to select a value to change, and then use the on-screen keypad to enter a new value.
Values entered for down payment will be subtracted from the property value to give a principal value.
If a percentage value for down payment is entered then that down payment percentage will remain fixed while changes in the property value will cause a change in the down payment amount.
If a non-percent value for down payment is entered then that down payment value will remain fixed while changes in the property value will cause a change in the down payment percentage.
The checkboxes on the left of the input boxes determine whether principal, interest, years or repayment is calculated. By default, the repayment checkbox is ticked, meaning that you can enter data in the prinicpal, interest and years boxes and the repayment will be calculated. Clicking on another checkbox, e.g. principal checkbox, allows you to modify years, interest and repayment to see the principal value calculated as these other values change.
The expenses figure shows the proportionate sum of tax, insurance, HOA and other expenses payable for the period being calculated. If PMI is enabled, an approximate value for PMI based on the downpayment percentage will be shown. The total payment for the period is the sum of the mortgage payment, PMI and expenses.
Extra payments can be made on a monthly, annual or one-time basis. They take effect when a valid corresponding month number is given. Enter 1 for the first month, 2 for the second month etc. Entering 0 prevents the extra payment from taking effect.
Six further one-time extra payments can be made giving the start and end months numbers to indicate the period when the extra payment is to be made.
Add five extra interest rates giving the start and end month numbers to indicate when the interest rate is active. Months outside these ranges will use the main interest rate. To specify a period where no principal is paid, enter a start and end month in the interest-only payments section.
Amortization Tables - shows how much interest and principal you pay broken down by year or by month. The monthly payments table shows the payment amount and any extra payment made each month - useful when extra payments reduce monthly payment. Space permitting, an extra "Total" field is added in landscape mode showing the total amount paid for that period.
Amortization Graph - shows how the monthly payments made each year are broken down. Note how the curves show increased principal and decreased interest being paid as time goes by. Also note that extra payments "push" up the principal curve, i.e. the annual principal amount shown is increased by the value of the extra payment.
Balance Graph - shows the balance outstanding over the term of the mortgage. It is useful when extra payments are made to visually see how much sooner the mortgage is paid off, and how quickly the balance drops.
Interest Graph - shows the rate of interest used over the term of the mortgage.
Repayment Chart - the percentage breakdown of the total payments made over the entire mortgage.
Loan Summary - a summary of your mortgage including information on savings in money and term when extra payments are made. Note that the total payments figure is for total principal and interest. Tax and insurance are not included.
Email report - this sends a summary of the current mortgage as an email attachent.
Settings menu - this lets you choose:
Payment frequency - most mortgages are paid monthly. If you change the payment frequency, you should probably change the compound period to match the payment frequency. Exceptions are Canadian and some UK mortgages.
Compound period - monthly is the standard compound period for amortization. This matches monthly payments. In Canada, payment frequency can be monthly but semi-annual compounding is used. In the UK, payments can be made monthly, but some Building Societies still use an annual rest system whereby interest is calculated once per year and the monthly payment is one twelfth of the annual payment due.
Rounding: no rounding means that full values are stored internally and rounding is only used when displaying values. Rounding means that every value stored internally is rounded to two decimal places using the selected rounding method. These internal values will match the displayed value. In this case, the final payment may be increased to compensate for rounding errors over the life of the loan.
Select what impact extra payments have: the default is to reduce term when extra payments are made, but the alternative is to keep term unchanged and reduce the monthly payment instead.
Private Mortgage Insurance (PMI) for the USA is an estimate based on MGIC standard 30 year fixed mortgage and the selected FICO credit score. Mortgage Insurance (MI) for Canada is based on Canada Mortgage Housing Corporation (CMHC) rates.
Annual tax can be entered as an exact figure or as a percentage of the property price. The resulting annual tax is divided by the payment frequency and included in the expenses figure.
Term in years or term in months.
Choose how year numbers are displayed in tables and graphs - you can show the calendar year or the year number.
Choose how month numbers are displayed in tables and graphs - you can show the calendar month, the payment number or the month/day of payment.
Whether to remove very large extra payments from the amortization graph - this stops one-off payment spikes distorting the graph scale.
Text can be display in white rather than the default colors.
A currency format other than the system default can be selected.
The app to launch when the menu's calculator button is pressed.
Enter the nominal interest rate not an APR.
Figures are estimates only - your lender's figures will inevitably vary!
Karl's Mortgage Calculator uses a standard amortization formula commonly used around the world. The figures generated by the calculator should therefore approximate what your lender will charge you, but you should always contact your lender for exact details on how and when they charge interest on outstanding principal balances.
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