Balloon Mortgage Calculator

Related Calculators

Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

Balloon payment: A large scheduled payment due near the end of a loan instead of paying the loan down to zero with normal monthly payments [1].

Regular monthly payment: The principal-and-interest payment based on the longer payoff plan, before any extra principal.

Payment based on payoff plan: The longer amortization schedule used to set the monthly payment, such as 30 years, even if the balloon is due sooner.

Balloon due after: The number of years of regular payments before the remaining balance comes due.

Extra principal: Extra money paid each month toward the loan balance. It reduces future interest and can lower the balloon payment.

Refinance cash gap: Balloon balance plus estimated refinance costs minus the estimated maximum refinance amount. Positive means cash needed; negative means room left over.

Loan-to-value (LTV): Loan size divided by home value. An 80% limit means the new loan is estimated at no more than 80% of the home's value.

Mistake: Entering the home price in Loan amount ($) when there is a down payment.
Fix: Enter only the amount borrowed, such as home price minus down payment.

Mistake: Using the balloon date for Payment based on payoff plan (years) .
Fix: Use the longer payoff plan that sets the monthly payment, often 15, 20, 25, or 30 years.

Mistake: Leaving Interest rate (percent per year) blank because the rate is unknown.
Fix: Enter the quoted fixed annual rate, or enter 0 only if the loan truly has no interest.

Mistake: Putting a negative number in Extra principal each month ($) to test a lower payment.
Fix: Use $0 or more; extra principal is an added amount paid toward the balance.

Mistake: Reading a negative Refinance cash gap as money you must bring to closing.
Fix: A positive gap means estimated cash needed; a negative gap means estimated refinance room left over.

Mistake: Entering Max refinance size (percent of home value) above 100.
Fix: Use a percent from more than 0 through 100, such as 80 for an 80% loan-to-value check.

• The monthly payment is principal and interest only. It excludes property taxes, homeowners insurance, HOA dues, mortgage insurance, escrow changes, late fees, and prepayment penalties.
• The calculator assumes a fixed interest rate and monthly payments. It does not model adjustable-rate changes, interest-only periods, or lender-specific payment rounding.
• The refinance check is a planning estimate. Real approval can depend on credit, income, debt-to-income ratio, appraisal, property type, lender rules, and market rates.
• Home value change (percent per year) is applied as a constant yearly growth rate. Actual home values can rise, fall, or move unevenly.
• Estimated refinance costs (percent of balloon) is added to the amount that may need refinancing. Real costs may be flat fees, percent-based fees, prepaid items, or lender credits.
• If the loan pays off before the balloon date, Balloon payment due is $0 and Paid off before balloon shows the payoff month.
• If Balloon due after (years) is longer than the payoff plan, the result is not a typical balloon setup because the loan may be scheduled to pay off first.

Payment calculation

The calculator first converts the annual interest rate to a monthly rate and converts years to months using 12 months per year.

monthly_rate = annual_interest_rate / 100 / 12

amortization_months = payment_based_on_payoff_plan_years * 12

If the monthly rate is 0, the payment is the loan amount divided by the number of amortization months.

regular_monthly_payment = loan_amount / amortization_months

If the monthly rate is greater than 0, the calculator uses the standard fixed-payment amortization formula.

regular_monthly_payment = loan_amount * monthly_rate * (1 + monthly_rate)^amortization_months / ((1 + monthly_rate)^amortization_months - 1)

Balance through the balloon date

After the regular payment is found, the calculator steps through each month until the balloon date or until the loan is paid off. Interest is added first, then the monthly payment plus any extra principal is applied. If the final payment would be more than the balance plus that month's interest, the calculator uses the smaller payoff amount.

interest = balance_start * monthly_rate

payment_used = min(regular_monthly_payment + extra_principal_each_month, balance_start + interest)

principal_paid = payment_used - interest

balance_end = balance_start - principal_paid

balloon_payment_due = balance_after_payments_through_balloon_date

Interest and total paid

The calculator adds the actual monthly payments used before the balloon date, including extra principal and any smaller final payoff payment.

principal_paid_before_balloon = loan_amount - balloon_payment_due

interest_paid_before_balloon = total_regular_payments - principal_paid_before_balloon

total_paid_if_balloon_is_paid = total_regular_payments + balloon_payment_due

Refinance gap check

If Home value now ($) is entered, the calculator estimates the future home value, the maximum refinance amount, and the cash gap. Balloon loans are often refinanced before the balloon payment is due, but refinancing usually means new loan terms and a new interest rate [3].

estimated_home_value_at_balloon_date = home_value_now * (1 + home_value_change_rate / 100)^balloon_due_after_years

estimated_max_refinance_amount = estimated_home_value_at_balloon_date * max_refinance_size_percent / 100

amount_to_refinance = balloon_payment_due * (1 + estimated_refinance_costs_percent / 100)

refinance_cash_gap = amount_to_refinance - estimated_max_refinance_amount

A positive refinance cash gap means estimated cash needed. A negative value is kept as a negative number because it means estimated refinance room left over.

Mini example

For a $300,000 loan at 6.5% interest with payments based on 30 years and a balloon due after 7 years, the regular principal-and-interest payment is about $1,896.20 per month. With no extra principal, the estimated balloon payment due is about $271,248.73. If the home is worth $375,000 now, grows by 2% per year, and the refinance limit is 80% with costs equal to 2% of the balloon balance, the estimated refinance cash gap is about -$67,931.99, meaning estimated refinance room left over.