Welcome to Thomas Foy's JavaScript Financial Calculations Page!

This page was created as an exercise in writing simple JavaScript functions and using the HTML MATH tag (the BOX and OVER tags didn't seem to work on my browser, so I left them out). If your browser can't handle JavaScript, this page will probably not work. Try Netscape 2.0 or above. I've tried to explain what the calculations do - if you have any questions or comments, please write me. I don't claim to follow any standard definition for the terms I use, and while I believe everything works correctly, I am not a financial expert so please use this for entertainment purposes only. If you think I should change, redefine, or add functions; or if something is really screwed up let me know. I've noticed that sometimes the return values are bogus, but entering the values again and recalculating seems to work. There is no error checking, and the results are give more than two decimal places. Enjoy!

INDEX


Future Value
The future value of $100.00 invested at 10% for one year would be $110.00. It is the value of the initial investment after the total investment period has passed, given a fixed rate of return. The future value of $100.00 invested at 10% for two years would be $121.00.

The equation I use to calculate Future Value is:

FutureValue = PresentValue*(1+PeriodicInterestRate/100)NumberOfPeriods
Enter Initial Investment (Present Value):
Enter Periodic Interest Rate:
Enter Number of Periods:

Future Value:
Back to the index.
Present Value
What will $100.00 be worth in a year, if inflation is 4%? It will be worth $96.15. What will it be worth in 10 years? $67.56. What will a millionaire thirty years from now be worth in today's dollars, assuming 4% inflation? $308,318.67. In general, present value is the equivalent dollar amount, in today's terms, of an amount at some time in the future given a fixed rate of inflation.

The equation I use to calculate Present Value is:

PresentValue = FutureValue/(1+PeriodicInflationRate/100)NumberOfPeriods
Enter Future Value:
Enter Periodic Rate of Inflation:
Enter Number of Periods:

Present Value:
Back to the index.
Future Value of an Annuity
Let's say you invest $100.00 a year for two years at a 10% annual percentage rate. How much will you have at the end of the year? $231.00.

The equation I use to calculate the Future Value of an Annuity is :

FVAnnuity = PeriodicDepositAmount*((1 + PeriodicInterestRate/100)1 + (1 + PeriodicInterestRate/100)2 + ... + (1 + PeriodicInterestRate/100)NumberOfPeriods)
Enter Periodic Deposit Amount:
Enter Periodic Interest Rate:
Enter Number of Periods:

Future Value:
Back to the index.
Present Value of an Annuity
Credit goes to Wayne and Edwina for the suggestion
Let's say you invest $100.00 a year for two years at a 10% annual percentage rate and the rate of inflation is 4%. What What is the equivalent dollar amount, in today's terms, of an amount you will have after two years? $213.57.

The equation I use to calculate the Present Value of an Annuity is :

PVAnnuity = (PeriodicDepositAmount*((1 + PeriodicInterestRate/100)1 + (1 + PeriodicInterestRate/100)2 + ... + (1 + PeriodicInterestRate/100)NumberOfPeriods)) /((1+PeriodicInflationRate/100)NumberOfPeriods)
Enter Periodic Deposit Amount:
Enter Periodic Interest Rate:
Enter Periodic Rate of Inflation:
Enter Number of Periods:

Present Value:
Back to the index.
Mortgage Payment
How much can you afford to borrow? Let's say you want to borrow $100,000.00 at 8% for 30 years. What will your monthly payments be? First, an 8% Annual Percentage Rate means an 8/12%, or 0.6667% monthly percentage rate. 30 years is 30*12 months, or 360 months. Plug these in to the form below, and you will find that the monthly payments would be $733.76.

The equation I use to calculate the Mortgage Payment is :

PeriodicPaymentAmount = LoanAmount*(PeriodicInterestRate/100)/(1-(1+PeriodicInterestRate/100)-NumberOfPeriods)
Enter Loan Amount:
Enter Periodic Interest Rate:
Enter Number of Periods:

Periodic Payment Amount:
Back to the index.

Retirement Income Table
Credit goes to Peter Merkle suggesting the following two calculations
You've saved quite a nestegg and are ready to hit the golf coarse, sailboat, beach, whatever. How much can you afford to spend without having to work again? For example, suppose you have a cool million in the bank and can get a steady 8% annual rate of return. You want to keep up with inflation though, so you've got to include a 4% inflation rate which means that the amount you withdraw will be greater every year - you'll actually be withdrawing a constant present value amount, not just a fixed amount. Also suppose you want to take out a value equivalent, in today's dollars (present value), to $100,000.00. How long will this last? Plug it in and you'll find that it will last over 12 years.
NOTE:Withdrawals are made at the end of the period and you may notice a few rounding errors (the variables are stored with more than two decimal places internally and numbers after the second decimal place are chopped off to format the table nicely).
Enter Initial Principle Amount:
Enter Present Value of Periodic Withdrawal:
Enter Periodic Interest Rate:
Enter Periodic Rate of Inflation:

Back to the index.

Periodic Withdrawal Estimate
Suppose you have a million dollars want to know how much you can withdraw for a given number of periods before the principle is gone. Try the following calculation. Given $1,000,000.00 at an 8% annual interest rate and 4% inflation with 5 years to spend it, you can withdraw a (present value) amount of $223,657.18 each of the five years before going broke.
Enter Initial Principle Amount:
Enter Number of Periods:
Enter Periodic Interest Rate:
Enter Periodic Rate of Inflation:
Withdrawal Rate:
Back to the index.
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