Mortgage Recast Calculator
Compare a lower recast payment with keeping the old payment after the same principal reduction.
Your inputs
Use consistent units and periods. Defaults are examples.
Your result
Check the assumptions below before relying on a result.
Formula and method
Calculate the original payment over the remaining term. After the selected month’s regular payment, subtract the lump sum. Recast payment uses that reduced principal, the unchanged rate and the months still remaining. The comparison option keeps the original payment and may finish earlier. Horizon cost = cash paid through that month + remaining principal, including the lump sum and applicable cash fee.
Worked example
200,000 at 6% over 240 months has a monthly payment of about 1,432.86. A 50,000 reduction immediately followed by a recast changes the payment to about 1,074.65. Keeping 1,432.86 after the same lump sum instead reduces the payoff time.
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Open calculator ↗How to use this result
- Use today’s balance and remaining term, not the original loan amount and original term.
- Choose an immediate or future principal reduction.
- Compare the payment reduction with the faster-payoff alternative.
- Inspect both complete schedules and include the fee when comparing a particular future month.
Questions about this calculation
Does a lump sum automatically lower my required payment?
Not in this model. The recast option explicitly recalculates the payment. A principal reduction alone with the old payment usually shortens the term.
Does recasting change my interest rate?
The scenario keeps the original contractual rate. A refinance replaces the loan and can have a different rate and term.
Is the lowest payment the cheapest choice?
Not necessarily. Keeping a higher payment after the reduction generally pays principal faster. Fees and the comparison horizon also matter.