Does the balance go down?

No — with interest-only payments the principal stays the same until the interest-only period ends.

What formula does the Interest-Only Payment use?

It calculates using Monthly interest = Loan × annual rate / 12. The guide above walks through what each part means with a worked example.

How accurate is the Interest-Only Payment?

It uses standard, widely-accepted financial formulas, so the math is exact for the figures you enter. Real-world numbers can differ once lenders, taxes, fees and rounding are applied, so treat the result as a close estimate rather than a formal quote.

Does the Interest-Only Payment include taxes and fees?

It includes only the fields shown on the form. Where inputs for extra costs (fees, taxes, insurance) are available, add them for a fuller picture — a real quote may still vary by provider.

Is this calculator free to use?

Yes — every GKCalculators calculator is 100% free with no sign-up required. Create a free account only if you want to save your calculation history across devices.

All calculations run instantly in your browser. Nothing is sent anywhere unless you tap ‘Explain my results’ (AI) or ‘Save’ while signed in.

Can I share my result?

Yes. Tap Share and we copy a link with your exact inputs baked in, so anyone who opens it sees the same result.

Interest-Only Payment

Monthly and annual interest-only payment on a loan balance.

Compare

Currency

Loan amount

Annual interest rate (%)

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Monthly interest payment

$1,625.00

principal unchanged

Annual interest

$19,500.00

Loan balance

$300,000.00

AI Breakdown & Smart Takeaway

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How the Interest-Only Payment works

The Interest-Only Payment Calculator instantly computes the monthly and annual interest payment owed on a loan balance when no principal is being repaid — ideal for borrowers, investors, and lenders evaluating interest-only mortgages, bridge loans, or investment property financing.

An interest-only payment is calculated by applying an annual interest rate to a principal loan balance and dividing by 12 to get the monthly figure. Unlike a standard amortizing loan where each payment chips away at both principal and interest, an interest-only arrangement means your payment covers only the cost of borrowing — the principal balance stays exactly the same until you begin repaying it or the interest-only period ends. This makes the math elegantly simple, but the financial implications are anything but.

The two variables that drive every result in this calculator are the loan balance (principal) and the annual interest rate. A higher balance multiplies the effect of the rate, which is why a 6% rate on a $500,000 mortgage produces a $2,500 monthly interest obligation, while the same rate on a $1,000,000 balance doubles that to $5,000. Even a modest rate change — say, moving from 6% to 7% — adds $417 per month on a $500,000 balance, underscoring why rate shopping matters so much for interest-only borrowers.

Interest-only periods are common on adjustable-rate mortgages (ARMs), jumbo loans, home equity lines of credit (HELOCs), and commercial real estate loans. Lenders typically allow an interest-only phase of 5 to 10 years, after which the loan recasts and begins amortizing over the remaining term. That recast moment is a critical planning point: your payment will jump significantly because you now owe the same original principal, compressed into fewer years. Borrowers who don't plan for this 'payment shock' are among the most common casualties of interest-only financing.

A frequent mistake is treating a low interest-only payment as free money — it is not; it is deferred cost. Every month in interest-only mode is a month in which you build zero equity through repayment (though property appreciation can still grow equity). Smart borrowers use interest-only periods strategically: to free up cash flow during a renovation, to maximize investment leverage when expected returns exceed the borrowing cost, or to manage income volatility during a transitional career period. Using this calculator to model both the current interest-only phase and the future fully-amortizing payment gives you the full picture before you commit.

Formula

Monthly interest = Loan × annual rate / 12

Pro tips

Always calculate what your payment will be after the interest-only period ends using a standard amortization calculator — compare that future payment to your current income projection before committing to the loan.
If your interest-only loan has a variable rate, run the calculator at both the current rate and a stress-tested rate (e.g., current rate + 2%) to ensure you can absorb rate increases without financial strain.
Making voluntary principal payments during the interest-only period reduces your balance, lowers future interest costs, and softens the eventual payment shock at recast — even small extra payments compound meaningfully over a 5–10 year IO period.
For investment properties, compare your annual interest-only payment directly against expected net rental income; a positive spread (rent minus interest) is a key indicator of near-term cash flow viability.
When comparing lenders, use this calculator alongside the APR (not just the stated rate) to get a true apples-to-apples cost comparison, since origination fees and points effectively increase your real borrowing cost.

Key terms

Principal: — The outstanding loan balance on which interest is being charged; in an interest-only loan, this amount does not decrease unless additional payments are made.
Interest-Only Period: — The defined phase of a loan — commonly 5 to 10 years — during which the borrower is required to pay only interest, with no mandatory reduction of the principal balance.
Loan Recast: — The point at which an interest-only loan converts to a fully amortizing schedule, requiring the original principal to be repaid over the remaining loan term, typically causing a significant payment increase.
Annual Interest Rate: — The yearly cost of borrowing expressed as a percentage of the loan balance; dividing this by 12 yields the monthly interest rate used in the payment calculation.
Payment Shock: — The abrupt and often large increase in required monthly payment that occurs when an interest-only loan recasts into a fully amortizing loan.
Amortization: — The process of gradually paying down a loan's principal balance through scheduled payments that include both interest and a growing portion of principal over time.