For lenders
Per diem interest calculator
Interest for one day, and for the period between two dates, on a 360-, 365- or 366-day basis. The figure a payout statement turns on, worked out the way a payout statement should work it out.
Free, no sign-up. It runs in your browser — nothing you type is sent to us or to anyone else.
Which basis applies is a term of the loan, not a convention — check the commitment before you quote a payout.
Counts the first day, not the last.
Per diem
$89.38
Interest for one day on $450,000.00 at 7.25%, on a 365-day year.
Interest for the period
—
Choose both dates.
How this is worked out
$450,000.00 × 7.25% ÷ 365 = $89.38 a day
Rounding is applied once, at the end. A lender that rounds the per diem first will be a few cents out over a long period — which is the sort of difference a borrower’s solicitor notices on a payout statement.
The detail
How this is worked out
The day-count basis is a term, not a convention
A 360-day year produces a larger daily figure than a 365-day year on the same rate, and which one applies is written into the commitment rather than decided by whoever prepares the statement. This asks you which basis the file uses instead of picking one quietly, because picking one quietly is how a payout goes out wrong.
Rounding happens once, at the end
The per diem is carried at full precision and rounded only when the total is worked out. Round the daily figure first and a sixty-day period can land several cents away from where it should — which is exactly the sort of difference a solicitor queries on a discharge statement.
The period counts the first day, not the last
Interest running from the 1st to the 31st is thirty days here, not thirty-one. That is the usual convention where interest runs to a discharge or payout date, but check it against the file: some agreements count both ends, and the difference is one day's interest on the whole balance.
It works on the balance you give it
The figure is calculated on the principal you type, so if the balance moves during the period — a payment lands, a further advance goes out — work each stretch separately and add them. A per diem on a stale balance is the second most common error on a payout statement, after the basis.
This is a calculator for your own working, not advice. It does not know the terms of your file or the rules you work under. Check anything that goes to a borrower, a client or a regulator against your own records first.
When one at a time stops being enough.
Loan Office does this as part of the work rather than as a separate calculation — on every file, with the result kept against the record it belongs to.