KaynatWorks · Home finance

Mortgage Payoff Strategy Planner

See how a lump sum, extra monthly principal or a recast could change your mortgage. Compare six strategies using the same loan and inspect every payment.

For fully amortizing, monthly fixed-rate mortgages. Principal and interest only. Your inputs stay in this browser and are not saved.

1. Your current mortgage

Use your latest statement. All amounts are in US dollars. Optional fields are marked.

Remaining principal ($)

Annual interest rate (%)

Loan type

Remaining term unit

Remaining term (years)

Years are rounded to the nearest month. A zero term is allowed only for a paid-off balance.

Monthly principal + interest ($, optional)

Exclude escrow, taxes and insurance. Leave blank to calculate from your balance and term.

Balance date

Start of the model, before the next payment.

Next payment date

Must be after the balance date. One full month of interest is modeled.

Maturity date (optional)

If supplied, must agree with the remaining term and payment dates.

2. Strategies to compare

Immediate lump sum ($)

Applies to the three lump-sum strategies on the balance date.

Extra monthly principal ($)

Starts with the next payment. Applies to both extra-payment strategies.

Target payoff method

Target payoff period (months)

Target strategy uses no lump sum. Zero requires an already-paid balance.

Estimates only · no account required

How the estimates work

The balance date is the start of the model. Each due date represents one full month of interest, even if the first date is less than a calendar month away. Later due dates keep the first payment’s day of the month, capped at month-end. This model does not calculate daily interest.

An immediate lump sum reduces principal on the balance date, before any interest accrues. Each month, interest accrues, the regular payment is applied, then extra principal is applied. Future lump sums in the engine apply after those payments; a recast changes the following month’s payment. The six comparisons here use an immediate lump sum.

The calculated principal-and-interest payment uses M = Br / [1 − (1 + r)⁻ⁿ], where B is the balance, r is the annual rate divided by 12, and n is remaining months. At 0% interest, M = B / n. A recast uses the reduced balance and original remaining term at the same rate.

Money is rounded to the nearest cent, with half cents rounded up. Each month’s interest is rounded before payments are applied. Totals sum the actual schedule. A calculated or recast payment settles any rounding residual on the final contractual payment; this can differ slightly from the usual payment. An entered payment stays fixed until the final capped payment, so a small residual can require another month. Balances never go below zero.

A fractional year is rounded to the nearest whole month. If you supply a maturity date, it must exactly match the final due date implied by your remaining term. Enter the payment from your statement for a comparison closest to your current mortgage; leaving it blank estimates a payment from the balance and term.

The target strategy uses no lump sum. It finds the smallest monthly payment, to the cent, that repays the rounded schedule within your period or on a due date on or before your target date. A later target can require a lower payment and cost more interest. Interest savings can therefore be negative.

Estimates exclude escrow, taxes, insurance, fees, penalties and tax effects. Recasting depends on your servicer’s eligibility rules, minimum principal reduction, processing time and fees. Confirm how extra payments are applied and request an official payoff quote before acting.

Learn more: CFPB guide to mortgage amortization.