Interest-Only Mortgage Calculator
Calculate interest-only mortgage payments during the introductory period and estimate payment shock when the loan recasts to full amortization.
What this calculator does
The Interest-Only Mortgage Calculator estimates your result instantly from the values you enter, using standard mortgages formulas. Calculate interest-only mortgage payments during the introductory period and estimate payment shock when the loan recasts to full amortization. Calculations run in your browser, so nothing you type is sent to a server, and the output is an estimate for planning rather than financial advice.
Interest-Only Mortgage Calculator Results
Interest-Only Monthly Payment
- Fully-Amortizing Payment (After Recast) —
- Payment Shock (Increase) —
- Percent Increase —
What This Means
About Interest-Only Mortgage Calculator
The Interest-Only Mortgage Calculator computes monthly payments during the introductory interest-only period and forecasts payment shock when the loan transitions into full amortization.
Formula & Mathematical Calculation
Interest-Only Monthly Payment = ( Loan Principal × Annual Interest Rate ) / 12
Amortizing Monthly Payment = Loan Principal × [ r(1 + r)^n_remaining ] / [ (1 + r)^n_remaining - 1 ]
Calculation Example
$500,000 Loan @ 6.5%: Years 1–10 Interest- Years 11–30 Fully Amortizing = $3,727.87/mo. Payment Shock = +$1,019.54/mo (+37.6%).
Key Benefits
- Calculates exact introductory interest-only monthly payments
- Models payment shock at the 5-year or 10-year recast milestone
- Evaluates total loan cost compared to standard 30-year fixed loans
- Essential for real estate investors using leverage strategies
- Prevents default risk by preparing borrowers for payment resets
How to Use this Calculator
-
Enter Loan Principal Amount
Input total borrowed mortgage amount. -
Set Interest-Only Period
Choose interest-only duration (commonly 5, 7, or 10 years). -
Review Payment Schedule
Click Calculate to see interest-only payments and amortizing recast payments.
Assumptions & Limitations
What the calculation assumes
- Every value you enter is treated as an exact, known amount.
- Rates and contributions are assumed to stay constant for the whole period unless the form asks for them separately.
- Results use standard financial formulas and ignore fees, penalties and promotional terms that are not entered above.
- Inflation, tax changes and market volatility are not modelled unless a field for them is provided.
- Amounts are unit-agnostic: results are returned in the same currency you enter.
What it does not cover
- Interest-Only Mortgage Calculator produces estimates for education and planning, not a quote, offer or professional advice.
- Real-world outcomes differ when fees, taxes, rounding rules or provider-specific terms apply.
- Local regulations and tax rules vary by country and change over time; verify current rules for your jurisdiction.
- Figures are only as accurate as the inputs you supply — check them before acting on the result.
- For decisions with lasting financial impact, confirm the numbers with a qualified professional.
Frequently Asked Questions
Free to use, no account needed. Calculations run in your browser, so nothing you type is sent to a server. Results are estimates — how we build and check our calculators.
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Next step: browse the full Mortgages calculators or read the related guides for context before you decide.