Intrest Only Calculator
An interest-only loan asks you to pay only the interest for a set period, so the payment is low and the balance does not move. This calculator prices that phase exactly: enter a loan amount, an annual rate and the length of the interest-only period in years, and it returns the monthly interest payment, the total interest across the period, the total paid, and the principal still owed at the end. It does not invent a payment for the phase after the period ends, and the article below is explicit about that limit.
Interest Only Payment Details
Quick Answer
On a $300,000 loan at 6% with a 5-year interest-only period, the monthly payment is $1,500.00, the 60 payments total $90,000.00 of interest, and the balance at the end of the period is still the full $300,000.00. Nothing in that payment reduces what you owe. The calculator is pre-filled with this exact case.
Key takeaways
- The monthly payment depends only on the amount and the rate: amount × rate ÷ 12. The length of the period changes the total interest, never the monthly figure.
- Total interest and total amount paid are the same number in this tool, because every dollar paid during the period is interest.
- The balance at the end of the period is the full loan amount. An interest-only period defers principal; it does not forgive it.
- This tool prices the interest-only phase only. The payment after the period ends needs the total loan term, which the tool does not ask for.
- Quick Answer
- How to use this interest-only calculator
- The interest-only formula, line by line
- Worked example: $300,000 at 6% for 5 interest-only years
- What this calculator does not show: the payment after the period ends
- Interest-only vs a standard amortizing loan, first five years
- Where interest-only periods show up in real loans
- What competing calculators miss
- Frequently asked questions
- Add This Calculator to Your Website
- References
How to use this interest-only calculator
Three inputs price the whole interest-only phase. There is no total-term field, no payment-frequency switch and no amortization table, and the steps below describe the tool as it actually works.
- Enter the loan amount. This is the balance interest is charged on for the entire period, because scheduled payments never reduce it.
- Enter the annual interest rate as a percentage from your loan note (6 for 6%). Use the note rate, not the APR: the APR bundles fees into a comparison figure and would inflate the payment. The monthly-rate conversion this tool performs is the same one broken down by the annual interest to monthly calculator.
- Enter the interest-only period in whole years. The tool reads whole years only: typing 2.7 years runs the calculation as 2 years. Match the whole-year period in your loan documents.
- Click Calculate. You get four lines: the monthly interest payment in large type, total interest paid, total amount paid during the period, and the remaining principal balance.
- Copy or share from the results box. The copied text restates all four lines, so a shared monthly figure never travels without the balance that stayed behind.
The interest-only formula, line by line
The monthly payment is the loan amount multiplied by the monthly rate, and every other output is that one number scaled by the period. There is no compounding inside the period, because the balance interest is charged on never changes.
Monthly interest payment = Loan amount × Monthly rate
Total interest = Monthly payment × (Years × 12)
Total amount paid (interest only) = Total interest
Remaining balance = Loan amount
Worked through with the pre-filled numbers: the monthly rate is 6 ÷ 100 ÷ 12 = 0.005, so the monthly payment is $300,000 × 0.005 = $1,500.00. Across 5 × 12 = 60 months that is $1,500.00 × 60 = $90,000.00. The last two lines look redundant until you see why they matter: total paid equals total interest because principal repayment is zero, and the remaining balance equals the starting amount for the same reason. A 0% rate is accepted and returns $0.00 payments, which is correct arithmetic for a zero-interest period. A negative amount, a negative rate, a blank field or a period of 0 years is rejected with a single message: “Please enter valid positive numbers for all fields.”
Worked example: $300,000 at 6% for 5 interest-only years
Every figure in this section is the calculator’s own output for the stated inputs, checked against the tool. Start with the rate, because the rate is what moves the monthly payment.
| Annual rate (5-year period, $300,000) | Monthly interest payment | Total interest over 5 years | Balance after 5 years |
|---|---|---|---|
| 4.5% | $1,125.00 | $67,500.00 | $300,000.00 |
| 6% (worked example) | $1,500.00 | $90,000.00 | $300,000.00 |
| 7.25% | $1,812.50 | $108,750.00 | $300,000.00 |
The period length works differently: it stretches the total without touching the monthly payment. At 6% on $300,000, a 3-year period totals $54,000.00 of interest, the 5-year example totals $90,000.00, and a 10-year period totals $180,000.00, at the same $1,500.00 every month. That is the trap in long interest-only periods: the payment feels manageable month to month while the meter keeps running on a balance that never shrinks.
What this calculator does not show: the payment after the period ends
The tool stops at the end of the interest-only period, by design. It never asks for the total loan term, so it cannot compute the amortizing payment that follows, and any page that quotes you a post-period payment from these three inputs alone is guessing at a term you never gave it.
The follow-on payment is still worth estimating by hand, with the assumption stated out loud. Suppose the $300,000 loan is a 30-year mortgage at a fixed 6%, interest-only for the first 5 years. The full $300,000 then amortizes over the remaining 25 years (300 payments) using the standard amortization formula, payment = balance × r(1 + r)n ÷ ((1 + r)n − 1) with r = 0.005 and n = 300. That gives about $1,932.90 a month, a jump of $432.90, roughly 29% above the interest-only payment. With a 10-year interest-only stretch inside the same 30-year term, only 20 years remain and the payment lands near $2,149.29. These two figures are hand calculations from the formula above, not outputs of the tool on this page; the rate is also assumed fixed, while many real interest-only loans adjust. To model the second phase month by month, run the same balance through the amortization schedule calculator, or compare the whole structure against a loan that amortizes from day one with the mortgage payment calculator.
Interest-only vs a standard amortizing loan, first five years
Over the first five years, the interest-only loan is cheaper per month and more expensive in total. The standard-loan column below is computed with the same amortization formula (a $300,000, 30-year loan at 6% amortizing from day one); the interest-only column is this tool’s output.
| First 5 years, $300,000 at 6% | Interest-only (5-year period) | Standard 30-year amortizing |
|---|---|---|
| Monthly payment | $1,500.00 | $1,798.65 |
| Total paid in 5 years | $90,000.00 | $107,919.00 |
| Interest paid in 5 years | $90,000.00 | $87,082.16 |
| Principal repaid | $0.00 | $20,836.93 |
| Balance after 5 years | $300,000.00 | $279,163.07 |
Where interest-only helps
- $298.65 less per month than the standard loan in this example, real cash-flow room for investors or variable income.
- Predictable, flat payments for the whole period at a fixed rate.
- Sensible for a property you expect to sell, or a loan you expect to refinance, before the period ends.
Where it costs you
- $2,917.84 more interest over the same five years, and a balance $20,836.93 higher.
- No equity built from payments; your ownership grows only if the property value does.
- A payment jump of roughly 29% or more when amortization starts, on a shorter remaining term.
Where interest-only periods show up in real loans
The same three-input math sits inside several real products. What changes between them is what happens when the period ends, which is exactly the part this tool leaves to your loan documents.
- Interest-only mortgages. Usually structured as adjustable-rate loans with a 5, 7 or 10-year interest-only phase, then full amortization over the rest of the term. Because an interest-only period is classed as a risky feature, these loans generally sit outside the Consumer Financial Protection Bureau’s qualified mortgage definition, and Regulation Z still requires the lender to judge your ability to repay using the fully amortizing payment, not the low interest-only one.
- HELOC draw periods. A home equity line of credit typically charges interest only on the drawn balance during its draw period, often 10 years; the same formula prices any drawn balance, and the HELOC strategy calculator covers the payoff planning that follows the draw.
- Construction and bridge loans. Interest is charged on amounts actually drawn while a project is built or a sale completes, then the loan converts or is repaid in full.
- Investor and business loans. Rental-property and commercial loans often run interest-only for a few years to keep debt service low against rental income, with a refinance or sale as the planned exit.
One tax note, stated narrowly: whether mortgage interest is deductible depends on the loan’s purpose and current tax law, and the rules are set out in IRS Publication 936. This calculator makes no tax assumption at all; its totals are gross interest, before any deduction.
What competing calculators miss
The formula is one line, so every serious rival gets the monthly payment right. The differences are in what surrounds it:
- Bankrate’s interest-only mortgage calculator: two inputs and a payment, from a trusted brand, but it stops at the monthly figure for a mortgage-only framing, with no total interest across the period stated next to it.
- Omni Calculator: adds payment frequency options and a clean worked example ($350,000 at 4% over 10 years), but the total cost of the period and the unchanged balance are left for the reader to infer.
- Rows and wpcalc: fast, minimal tools (wpcalc even auto-calculates as you type), with thin explanation and no treatment of what the period costs in total.
- calculator.now, graphcalc and MultiCalculatorHub: these do compute a post-period amortizing payment, which is genuinely useful, but only by quietly assuming a total term; readers can easily take that second payment as this tool’s job too, without seeing the assumption.
- The gap this page fills: the full period priced in four explicit lines (monthly, total interest, total paid, balance), an open statement that total paid equals total interest and why, the whole-year reading of the period input disclosed rather than hidden, and the post-period payment shown only as a clearly labelled hand calculation with its term assumption printed next to it.
Frequently asked questions
It prices the interest-only phase only: the monthly interest payment, the total interest across the period, the total amount paid during the period, and the principal balance left at the end, which is the full amount you borrowed.
Because every payment in the period is interest. Nothing goes to principal, so the amount you hand over during the period equals the interest charged during the period, dollar for dollar.
No. That payment depends on the total loan term, which this tool does not ask for. As a hand calculation, a $300,000 loan at 6% with 5 interest-only years inside a 30-year term re-amortizes over the remaining 25 years at about $1,932.90 a month.
Each monthly payment covers only the interest charged that month, so no part of it reduces the principal. The balance on the last day of the period is the same as on the first day, unless you make voluntary extra principal payments.
The tool reads the period as a whole number of years, so 2.7 years is treated as 2 years and 5.9 years as 5 years. Enter the whole-year period from your loan documents for an exact match.
Yes. A 0% rate is accepted and returns a $0.00 monthly payment and $0.00 total interest, which is the correct arithmetic for a zero-interest loan or a fully subsidized period. Negative rates, negative amounts and a period of 0 years are rejected.
Generally no. The Consumer Financial Protection Bureau’s qualified mortgage rules treat an interest-only period as a risky feature that keeps a loan out of qualified mortgage status, so these loans are usually non-QM products, and lenders must still judge your ability to repay the fully amortizing payment.
Many loans allow it, but check your note for prepayment terms first. This calculator models scheduled payments only, so voluntary principal payments, which would lower your balance and every later interest charge, are not included in its results.
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References
- Consumer Financial Protection Bureau. What is a Qualified Mortgage?. Accessed October 22, 2026.
- Consumer Financial Protection Bureau. Regulation Z, Section 1026.43: Minimum standards for transactions secured by a dwelling. Accessed October 22, 2026.
- Cornell Law Institute, Legal Information Institute. 12 CFR 1026.43: Minimum standards for transactions secured by a dwelling. Accessed October 22, 2026.
- Internal Revenue Service. Publication 936: Home Mortgage Interest Deduction. Accessed October 22, 2026.
- Board of Governors of the Federal Reserve System. Interagency Guidance on Nontraditional Mortgage Product Risks. Accessed October 22, 2026.
- Office of the Comptroller of the Currency. Federal Financial Regulatory Agencies Issue Final Guidance on Nontraditional Mortgage Product Risks (News Release 2006-107). Accessed October 22, 2026.
- Federal Deposit Insurance Corporation. Affordable Mortgage Lending Guide, Part III. Accessed October 22, 2026.
- Board of Governors of the Federal Reserve System and Office of Thrift Supervision, via FRASER, Federal Reserve Bank of St. Louis. Consumer Handbook on Adjustable-Rate Mortgages (CHARM booklet). Accessed October 22, 2026.
- Board of Governors of the Federal Reserve System. Testimony on non-traditional mortgage products, September 20, 2006. Accessed October 22, 2026.
- U.S. Department of Housing and Urban Development. About Housing Counseling. Accessed October 22, 2026.