# Interest Only Mortgage Calculator

> Estimate payments and total interest for a mortgage with an initial interest-only period followed by amortizing payments.

Page: https://askcalculators.com/calculator/interest-only-mortgage-calculator/
Definition: https://askcalculators.com/calculator/interest-only-mortgage-calculator/definition.json
JSON Schema: https://askcalculators.com/calculator/interest-only-mortgage-calculator/schema.json
Version: 1.0.0
Maintained by: AskCalculators (software project; not a credentialed reviewer)
Qualified review: pending. Automated checks do not establish professional approval.
Page status: Live
Review status: Pending

## Use
Open the calculator page and enter values. Query-string parameters can restore and bookmark a calculation.
Example: https://askcalculators.com/calculator/interest-only-mortgage-calculator/?loanAmount=400000&annualRate=6.5&totalTermYears=30&interestOnlyYears=10

## Inputs
- loanAmount: Mortgage principal; type=money; required; default=400000; min=0.01
- annualRate: Annual interest rate; type=percent; required; default=6.5; min=0; max=100
- totalTermYears: Total mortgage term in years; type=number; required; default=30; min=1; max=50
- interestOnlyYears: Interest-only years; type=number; required; default=10; min=0; max=49

## Outputs
- interestOnlyPayment: Monthly interest-only payment; format=currency; primary
- amortizingPayment: Monthly payment after interest-only period; format=currency
- paymentIncrease: Payment increase; format=currency
- totalInterest: Total interest over full term; format=currency
- totalPaid: Total paid; format=currency

## Formula
interest-only payment = principal × annual rate ÷ 12; remaining principal is amortized over the remaining term

## Rules
- Empty optional inputs are undefined, not zero.
- Hidden conditional inputs are ignored.
- Do not invent missing required inputs.

Notice: Mortgage terms, escrow, insurance, taxes, fees, and adjustable-rate provisions can materially change actual payments.