Calculate interest accrued over a specific number of days.
The annual rate is converted to a daily rate by dividing by 365.
That daily rate is applied to the principal for the number of days specified.
Daily rate: Annual rate ÷ 365
Interest: Principal × daily rate × days
The daily interest calculator finds the interest on a sum for a given number of days. It converts the annual rate into a daily rate by dividing by 365 and then applies that rate to the principal for each day, without compounding.
Many situations need interest for a period that is not a neat number of months. A loan paid off in the middle of a month, a short gap between a cheque bounce and repayment, interest on a delayed payment, or the broken period between loan disbursement and the first EMI date all need a day count. Savings accounts in India also compute interest on the daily closing balance.
The calculator answers a simple question: at this annual rate, how much interest builds up on this amount over this many days?
1. Note the principal P and the annual rate R%.
2. Compute the daily rate as a decimal: d = R ÷ 365 ÷ 100.
3. Count the days D, usually excluding the start date and including the end date.
4. Interest = P × d × D, which is the same as P × R × D ÷ 36500.
5. If the balance changes during the period, split the period at each change and add the interest for each part.
6. Add the interest to the principal if you need the total amount due.
The formula P × R × D ÷ (365 × 100) is ordinary simple interest, with time measured in days and converted to years by dividing by 365. It assumes interest does not compound within the period. For short periods this is how most interest is actually computed: savings accounts calculate daily and credit it quarterly or half-yearly, and loans often charge broken-period interest by the day. Over a few weeks or months, compounding would change the answer only slightly, so the simple form is both easier and accurate enough.
Dividing by 365 is the most common convention in Indian retail banking, but not the only one. Some money market instruments use 360 days, and in leap years some lenders divide by 366 or use actual days over actual days. The choice changes the answer slightly: using 360 gives about 1.4% more interest than using 365 for the same days. Counting days also needs care. Banks usually count from the day after the deposit or disbursement up to and including the day of repayment.
A daily rate looks tiny. At 10% a year it is only about 0.0274% a day. Small daily numbers can hide large annual costs, which is why some short-term apps quote daily rates. Multiply a daily rate by 365 to see the annual figure. If interest is actually added to the balance every day, the effective annual rate is (1 + d)³⁶⁵ − 1, a little above the nominal figure, but this calculator reports the simple, non-compounded interest.
Jayesh repays a ₹2,50,000 bridge loan from a relative 45 days after taking it, and they agreed on interest at 10% a year.
Answer: Interest for this period ₹3,082; Daily rate 0.0274%
Counting both the start and end dates, adding an extra day of interest.
Dividing the monthly rate by 30 instead of the annual rate by 365, which gives a slightly different answer.
Applying the rate to the original principal when part of it was repaid during the period.
Ignoring that the lender may use a 360-day year.
Calculating interest on a loan closed in the middle of a month.
Working out broken-period interest before the first EMI.
Estimating savings account interest on a balance held for a few days.
Settling interest on short personal loans between friends or family.
Where is daily interest actually used?
It is commonly used for savings accounts, short-term loans, and working out the exact interest for part of a month, or for a loan paid off early.