How to calculate interest on Saving account?

Formula to calculate the interest on Saving account: 

Amount * ROI / 100 * No Of Days / 365

Here Amount is the base amount available in your account.

ROI: Rate of interest which your bank is providing you on your saving account.  

No of days: Total number of days that amount remain in your saving account.

lets take an example:

I have a saving account in state bank of India. State bank gives 4% rate of interest annually on saving accounts and I kept rupees 100,000 in my saving account for 15 days. Then how much interest I will earn from this.

Amount: 100000

ROI: 4

No of Days: 15 

lets calculate using the formula:

Total interest = Amount * ROI / 100 * No Of Days / 365

= 100000 * 4/100 * 15/365

 = 164.38

Total interest a account holder will earn 164.38 rupees in 15 days on the amount of rupees 100000.