Mortgage Duration Calculator

How to use this calculator

1. Enter your current mortgage balance (loan amount), annual interest rate (APR), and monthly principal-and-interest payment.
2. We solve for how many monthly payments it would take to fully pay off the loan at that payment level and rate.
3. We convert the result into both months and years so you can see your approximate payoff timeline.
4. We compute the total interest you would pay over that payoff period.
5. Use the results to decide whether your current payment is aggressive enough or if you want to adjust your payoff strategy.

Inputs explained

Loan amount

Your current mortgage balance (remaining principal), not the original loan amount. You can find this on a recent statement.

Interest rate (APR %)

The annual percentage rate on your mortgage. Use the current effective rate for your loan if it has adjusted.

Monthly payment

The principal-and-interest portion you plan to pay each month. Exclude escrow items like taxes, insurance, and HOA dues so the model focuses on the loan itself.

When to use it

• Estimating mortgage payoff time when you increase or decrease your monthly payment.
• Checking how far a proposed new payment will move your payoff date compared to the original schedule.
• Planning budgets to hit a desired payoff date, such as before retirement or before kids start college.
• Comparing different payment levels to see how much interest you could save by paying extra each month.
• Helping visualize the impact of refinancing or recasting on payoff time, once you know the new payment amount.

Tips & cautions

• If your monthly payment is only slightly above the interest charge, the payoff timeline can be very long; increasing the payment even modestly can save years and significant interest.
• Always enter the principal-and-interest payment, not the total escrowed payment, so the payoff math is accurate.
• Use this in combination with an extra-payment or biweekly calculator to model more advanced payoff strategies.
• Revisit the calculation after refinancing, recasting, or making a large lump-sum payment, since your balance and payment will change.
• Consider whether the payoff timeline aligns with your life plans; if not, adjust your payment or refinance options accordingly.
• Assumes a fixed-rate loan with constant monthly payments; adjustable-rate mortgages or loans with frequent rate changes are not fully captured.
• Does not account for extra principal payments, lump sums, fees, or prepayment penalties.
• Focuses on principal and interest only; it ignores escrow, property taxes, homeowners insurance, PMI, and HOA dues.
• If the monthly payment is too low to cover the interest due, the loan would negatively amortize and payoff time becomes undefined; in that case, the model will not produce a meaningful result.

Deep dive

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