Mortgage Payoff Calculator
Every extra dollar paid against a mortgage removes principal that would otherwise be charged interest for the rest of the term. A modest extra payment can cut years off the loan and save tens of thousands.
Interest saved by paying extra
$64,928.60
- Required monthly payment
- $1,688.02
- Months with the extra
- 233.8308
- Months saved
- 66.1692
- Interest without extra
- $256,405.37
- Interest with extra
- $191,476.77
Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.
The formula this calculator uses
Months with extra = -ln(1 - rate x balance / (payment + extra)) / ln(1 + rate)
- balance
- Amount still owed today
- rate
- Annual rate divided by twelve
- payment
- Required monthly payment
- extra
- Additional principal paid each month
How to check the result by hand
- 1
Find the current payment
Use the scheduled monthly payment on the outstanding balance at the current rate. This is the baseline before any extra.
- 2
Compute interest without extra
Multiply the payment by the remaining months and subtract the balance. That is the interest you would pay if you changed nothing.
- 3
Solve for the new payoff time
Plug the larger payment into the payoff formula using a logarithm. The result is the month the loan reaches zero with the extra.
- 4
Compute interest with extra
Multiply the larger payment by the shorter term and subtract the balance. That is the interest you pay with the extra.
- 5
Subtract for the saving
The difference between the two interest totals is your saving, and the difference in months is the time you take off the loan.
For worked examples, common mistakes and the limits of this formula, read the full How To Calculate Mortgage Payoff page.