An interest-only payment covers only the interest that has accrued on a loan, not the principal balance itself

When you make an interest-only payment, your money goes toward the cost of borrowing—the interest—and leaves the amount you originally borrowed untouched. If you borrowed $200,000 at 5% annual interest, an interest-only payment might be around $833 per month, and that entire amount pays interest. The $200,000 principal stays the same. After 12 months of interest-only payments, you still owe $200,000.

Interest-only payments are most common on mortgages, home equity lines of credit (HELOCs), and some personal loans or business loans. They are rarely offered on car loans or credit cards. The structure is simple: the lender calculates what you owe in interest each month and that becomes your payment. Nothing reduces what you borrowed.

Key Takeaways

  • An interest-only payment covers only accrued interest and does not reduce your loan balance at all.
  • Interest-only periods typically last 5 to 10 years on mortgages, after which payments jump to include principal repayment.
  • Your total payment is lower during the interest-only phase, but you build no equity and owe the full original amount when the period ends.
  • When the interest-only period ends, your monthly payment increases significantly because you now pay both interest and principal over the remaining loan term.

How the payment amount is calculated

The lender takes your loan balance and multiplies it by the annual interest rate, then divides by 12 to get the monthly interest charge. If your loan is $300,000 and your rate is 4%, the annual interest is $12,000. Divided by 12 months, your interest-only payment is $1,000 per month. That calculation stays the same each month as long as the interest rate does not change and you do not pay down the principal.

If your loan has a variable interest rate—common on HELOCs and some adjustable-rate mortgages—your payment will change when the rate changes. A rate increase means a higher interest-only payment. A rate decrease means a lower one. The principal balance never moves unless you make an extra payment that is specifically applied to principal, which most lenders allow but do not require during the interest-only phase.

When interest-only periods end and what happens next

Most mortgages with an interest-only option have a set period—often 5, 7, or 10 years—during which you pay only interest. When that period ends, your loan enters the amortization phase. Now your payment must cover both interest and principal, and it is calculated so that you will pay off the entire remaining balance by the loan's maturity date.

This transition creates a payment shock. If you borrowed $400,000 at 4% with a 10-year interest-only period followed by a 20-year amortization, your interest-only payment is about $1,333 per month. When year 11 arrives, your payment jumps to roughly $2,400 per month—nearly double—because you now have 20 years to repay $400,000 plus remaining interest. The exact new payment depends on how much principal you paid down (if any) and the remaining term.

Why lenders offer interest-only payments

Lenders use interest-only options to make loans more attractive to borrowers who expect their income to rise, who plan to sell the property before the interest-only period ends, or who want the lowest possible payment in the short term. A buyer who cannot yet afford a full principal-and-interest payment might may have access to for an interest-only mortgage when they would not may have access to for a traditional one. The lower initial payment also appeals to investors who buy rental properties and want to minimize cash outflow early on.

From the lender's perspective, interest-only loans carry more risk because the borrower builds no equity during the interest-only phase. If property values fall or the borrower's income drops, the borrower may owe more than the property is worth or be unable to afford the payment jump. For this reason, interest-only mortgages typically require a larger down payment and a higher credit score than conventional loans.

The difference between interest-only and principal-and-interest payments

A principal-and-interest payment (also called a fully amortizing payment) divides your monthly payment between both components from day one. On a $300,000 loan at 4% over 30 years, your payment is about $1,432 per month. In the first month, roughly $1,000 goes to interest and $432 to principal. By month 360, almost all of it goes to principal because the balance is nearly paid off. Over the life of the loan, you pay the same total interest as you would on an interest-only loan followed by amortization—but you own more of the property sooner.

With interest-only, you pay less each month during the interest-only phase but more total interest over the life of the loan if you keep the property long enough. You also own zero percent of the property (in terms of equity) until the interest-only period ends and you start paying principal. If you sell during the interest-only phase, you owe the full original amount to the lender, and the profit (if any) is yours. If you hold through the amortization phase, your equity grows with each principal payment.

Risks of interest-only loans

The biggest risk is the payment jump. If you cannot afford the new payment when the interest-only period ends, you may have to refinance, sell, or default. Refinancing is only an option if your credit and income still may have access to and if interest rates have not risen. If rates have climbed, your new payment could be even higher than the amortized payment would have been.

A second risk is negative amortization on some variable-rate interest-only loans. If the interest rate rises and your payment is capped (does not increase), the unpaid interest gets added to your principal balance. You end up owing more than you borrowed. This is rare on mortgages but more common on HELOCs with payment caps.

A third risk is property value decline. If your home or investment property loses value and you still owe the full original amount, you may be underwater—owing more than it is worth. This makes selling difficult and refinancing impossible.

Interest-only payments on different loan types

Mortgages are the most common use of interest-only payments. A borrower might take a 10-year interest-only mortgage if they plan to sell in 8 years or expect a significant income increase. HELOCs often default to interest-only payments during the draw period (usually 5 to 10 years), then shift to principal-and-interest payments during the repayment period. Some personal loans and business loans offer interest-only options, but the lender sets the terms—there is no standard structure.

Credit cards never use interest-only payments in the traditional sense. You can pay only the interest accrued each month, but the card issuer does not require it; they simply accept whatever payment you make. Paying only interest on a credit card means your balance never shrinks, and you pay interest on interest indefinitely. Car loans almost never offer interest-only payments because the lender wants the car's value to be covered by the principal paid down over time.

Frequently Asked Questions

Can I pay principal during an interest-only period?

Yes. Most lenders allow you to pay extra toward principal at any time without penalty. Paying principal during the interest-only phase reduces your balance and the interest you owe later. When the amortization phase begins, your payment is calculated on the lower remaining balance, so the payment shock is smaller.

What happens if I cannot afford the payment when the interest-only period ends?

You can refinance the loan into a new mortgage with a new term, though you must still may have access to based on current credit and income. You can also sell the property. If you cannot do either and cannot afford the new payment, you risk default and foreclosure. Planning for the payment increase before it happens is critical.

Is an interest-only loan a good idea?

It depends on your situation. Interest-only works if you plan to sell before the period ends, expect income to rise significantly, or want to minimize cash outflow short-term. It is risky if you plan to keep the property long-term and cannot afford the payment jump, or if you are betting on property values rising to cover the risk.

How much interest will I pay on an interest-only loan compared to a regular mortgage?

The total interest is usually similar or slightly higher because you are not paying down principal during the interest-only phase. However, if you sell during that phase, you pay less total interest than you would on a 30-year amortizing loan. The math depends on how long you keep the loan and what happens to interest rates.

Can interest-only payments change if my interest rate is variable?

Yes. If your loan has a variable rate, your interest-only payment changes when the rate changes. A rate increase raises your payment; a rate decrease lowers it. Fixed-rate interest-only loans have the same payment throughout the interest-only period.