How the interest rate calculation happen in PPF?

[Vivek]

NSC provide net amount after 6 year as per interest rate mentioned at the time of NSC purchase (example- A bought NSC of Rs.10000/- at the rate of 8%, he will get Rs.16010/- after 6 year). But interest rate of PPF vary time to time, govt changes it year on year basis. My query is - If at the time of PPF a/c opening interest rate is 8% and after 1-year, it increases to 9% then which interest rate will be applicable? and what amount will investor get after 15 year?

[Rahul]

The rate of interest will be calculated on the lowest balance in the account between the close of the fifth day and the end of the month and will be credited to your account at the end of the year.
More info - http://www.policywala.com/content.php/177-How-to-get-maximum-return-out-of-PPF-account
Similar thread -
http://www.policywala.com/forum/showthread.php/1965-Query-on-PPF-account-interest-calculation-and-tax-benefit

[VarunD]

268 You can do calculation yourself with the attached excel PPF calculator. First enter deposit amount with 8% for one year then deposit amount with 9% for next 14 years.