Mortgage Recast Calculator
Your new payment after a lump sum is paid and the loan is recast at the same rate and term, compared with keeping the payment and finishing early.
Result…
How it's calculated
Current payment = B × i ÷ (1 − (1 + i)^−n), i = yearly rate ÷ 12, n = months left Recast payment = (B − lump sum) × i ÷ (1 − (1 + i)^−n) Interest = payment × n − balance Keep payment: each month balance × (1 + i) − current payment, until zero
A recast (re-amortisation) keeps your rate and end date but spreads the smaller balance over the months that are left, so the payment falls. Keeping the old payment instead pays the loan off sooner and saves more interest, while a recast frees up cash each month. Both start from the same lump sum.
Your numbers, step by step
About the Mortgage Recast calculator
This mortgage recast calculator shows what happens to your payment after a lump sum. In a recast, also called re-amortisation, the lender keeps your rate and end date and spreads the smaller balance over the months that are left, so the monthly payment falls. Enter the current balance, the rate, the years left, the lump sum and any recast fee. The calculator gives the new payment and the interest saved, then compares the other choice: keeping the old payment and paying the loan off early. That comparison matters, because one frees up cash each month while the other saves more interest. The steps show each figure with your numbers, and the chart sets the interest of both choices side by side.
How to use it
- Enter the “Current balance”, the “Interest rate” and the “Years left”.
- Enter the “Lump sum” you plan to pay off the balance.
- Enter the “Recast fee” if your lender charges one.
- Read the new monthly payment and the payment reduction.
- Compare the recast's interest saving with keeping the old payment and finishing early.
Worked example
A 250,000 balance at 6% with 25 years left costs 1,610.75 a month. Paying 50,000 off and recasting the 200,000 left over the same 25 years brings the payment to 1,288.60, a cut of 322.15 a month, and saves 46,395.21 in interest after a 250 fee. Keeping the 1,610.75 payment instead clears the loan 105 months sooner and saves 120,034.56.
Updated
Questions people ask
How is a recast mortgage payment calculated?
Take the balance after the lump sum and work out the standard payment over the months left: (balance − lump sum) × i ÷ (1 − (1 + i)^−n), where i is the yearly rate divided by 12.
Is a recast the same as a refinance?
No. A recast keeps your loan, rate and end date and only lowers the payment. A refinance replaces the loan with a new one, usually with new costs; compare that with the mortgage refinance calculator.
Should I recast or keep paying the same amount?
Keeping the payment saves more interest and ends the loan sooner. A recast lowers the payment, which helps if you want more spare cash each month. The calculator shows both so you can weigh them.
Why does a recast save less interest than paying early?
After a recast you pay less principal each month, so the balance falls more slowly than if you had kept the old payment, and interest keeps building on it for longer.
Can every mortgage be recast?
No. Some lenders and loan types do not offer it, and minimum lump sums and fees vary by lender and country. Ask your lender what applies, or speak to a mortgage adviser before paying a large sum in.