Lump Sum Mortgage Payment Calculator
See how a one-time lump sum payment toward your mortgage principal reduces your remaining term and total interest.
Loan Details
Impact of Lump Sum
Interest Saved
Time Saved
| Without Lump Sum | With Lump Sum | |
|---|---|---|
| Monthly Payment | — | — |
| Remaining Balance | — | — |
| Total Interest | — | — |
| Payoff Time | — | — |
How Lump Sum Payments Work
A lump sum mortgage payment is a one-time extra payment applied directly to your principal balance. Unlike regular overpayments, the impact is immediate — your balance drops by the full lump sum amount, and all future interest calculations are based on the reduced balance.
The "return on lump sum" shown above represents how much interest you save per dollar of lump sum paid. For example, a 2.5x return means every $1 of lump sum saves you $2.50 in interest over the remaining life of the loan.
Best Times to Make a Lump Sum Payment
- Early in the loan — The earlier you pay, the more compounding interest you avoid
- After receiving a windfall — Tax refunds, inheritance, bonuses, or asset sales
- When rates are high — Higher rates mean more interest saved per dollar of principal reduction
- Before a rate reset — If you have an adjustable-rate mortgage, reducing principal before a rate increase limits exposure
Lump Sum vs Monthly Overpayment
A lump sum reduces your balance immediately, so you save interest from day one. Spreading the same amount as monthly overpayments saves less total interest because the balance reduces gradually. However, monthly overpayments are more sustainable for most budgets.