Loans and mortgages Updated November 2026

Total interest paid on a loan

Total interest over the life of an amortizing loan is PMT x n minus the amount borrowed. For a 200,000 mortgage at 6% over 30 years that is 1,199.10 x 360 - 200,000 = 231,676.38, more than the loan itself. Excel's CUMIPMT gives the interest paid between any two payments.

Syntax

total interest = PMT x n - P

Part	What it is
`PMT`	Periodic payment
`n`	Number of payments
`P`	Amount borrowed

Examples

200,000 at 6%, 30 years
1,199.10 x 360 - 200,000

Result: Total interest = 231,676.38

Excel: =-CUMIPMT(6%/12, 360, 200000, 1, 360, 0)

200,000 at 6%, 15 years
1,687.71 x 180 - 200,000

Result: Total interest = 103,788.46 (saves 127,888 versus 30 years)

15,000 car loan at 5%, 48 months
345.44 x 48 - 15,000

Result: Total interest = 1,581.09

Common mistakes

Multiplying P x rate x years (200,000 x 6% x 30 = 360,000) treats the loan as if the full balance were owed the whole time; the balance declines, so true interest is lower.
Using the rounded payment in the multiplication and then comparing to a lender's figure; small cent differences accumulate over 360 payments.
Forgetting that CUMIPMT needs the principal entered as positive and returns a negative number; put a minus sign in front.

Practice Total interest paid on a loan

These drills check your answer on live data, free, no account needed.

Total interest over the loanYou borrow $105,000 for 30 years at 4.25% APR with monthly payments. Using the payment rounded to the cent, how much interest do you pay over the life of the loan?
Interest part of payment kA $105,000, 30-year mortgage at 4.25% APR has a monthly payment of $516.54. How much of payment number 85 is interest?

Questions

How much interest do I pay on a 30-year mortgage?

At 6% on 200,000, about 231,676, or 1.16 times the loan. At 7% it is 279,018 and at 5% it is 186,512.

How do I calculate total interest in Excel without a schedule?

=PMT(rate, n, -P)*n - P, or =-CUMIPMT(rate, n, P, 1, n, 0). Both give the same total.

Mortgage payment formulaHow to calculate a monthly mortgage payment with M = P x r / (1 - (1 + r)^-n). Examples for 200,000 at 6% and 300,000 at 5%, Excel PMT and common mistakes.
Amortization scheduleAn amortization schedule splits each payment into interest and principal and tracks the balance. Worked schedule for a 10,000 loan, Excel IPMT and PPMT.
Extra payments and payoff timePaying extra each month shortens the loan: n = -ln(1 - P x r / PMT) / ln(1 + r) with the higher payment. Example: 200 extra on 200,000 saves 9 years, 79,800.
Car loan paymentHow to calculate a car loan payment with PMT = P x r / (1 - (1 + r)^-n). Examples for 20,000 at 7% over 60 months and 15,000 at 5%, total interest, Excel.