Finance category
Mortgage, loan, investing, tax, and money calculators.
Per Diem Interest Calculator
Mortgage closings collect interest from closing day through end of month as a prepaid. This calculator sizes the per-diem amount so you can reconcile it on the Closing Disclosure.
Per-diem interest at closing
$641
included in prepaids
Daily interest
$71.20
Days collected
9
How the math works
Per-diem interest covers the gap between closing and the start of the first full month. Mortgages conventionally have the first payment due the month AFTER the first full month — so a June 22 closing has per-diem through June 30, then a first mortgage payment August 1 covering July interest.
Closing early in the month collects more per-diem upfront but produces the same first-payment timing. Some buyers pay "interim interest" by closing late in the month to minimize out-of-pocket at closing. The tradeoff is a sooner first payment.
How to Use
- Enter loan amount and rate.
- Enter the closing day of the month.
- Enter days in the closing month.
- Pick day-count basis — Actual/365 for most residential mortgages.
Frequently Asked Questions
Why is per-diem so high when I close early in the month?
More days to month-end means more interest. Closing on the 2nd collects ~28 days; closing on the 28th collects ~2 days. Late-month closings reduce cash needed at closing but accelerate the first payment.
Is per-diem negotiable?
The amount isn't, but the closing date is. If cash-tight, negotiate a late-month closing to reduce per-diem. If cash-flush, close early to use seller proceeds efficiently and stretch to the next first payment.
Does per-diem affect APR?
Yes — it's a finance charge included in APR calculation. A high per-diem at a long-closing-to-month-end can push APR materially above the note rate.
Related Calculators
Daily Interest Calculator
Daily accrual for any balance.
Prepaid Interest Calculator
Broader prepaid interest calc.
Closing Cost Calculator
Full closing cost picture.
Closing Disclosure Calculator
Reconcile the final CD.
APR Calculator
Per-diem's effect on APR.
Refi Cash to Close Calculator
Refi per-diem at payoff.
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