Mortgage Assumption Calculator
Calculate exactly how much you save by assuming a seller's existing mortgage instead of taking out a new loan at today's higher rates. Compare assumed vs new loan payments side by side, see total interest savings over the remaining term, and find out the cash you need to cover the equity gap — free, private, no sign-up required.
| Metric | Assumed Mortgage | New Mortgage (Market Rate) | Difference |
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What Is a Mortgage Assumption and How Does It Work?
A mortgage assumption is a transaction in which a home buyer takes over the seller's existing mortgage, including its original interest rate, remaining balance, and remaining term. Instead of applying for a brand-new mortgage at today's rates, the buyer "assumes" the seller's loan and continues making the same monthly payments. The seller is released from liability (with lender approval), and the buyer steps into the borrower role.
According to the Consumer Financial Protection Bureau (cfpb.gov), mortgage assumptions are most valuable when the seller's rate is significantly below current market rates. With 30-year fixed rates at or above 6.5%–7% in 2025–2026, a seller who locked in a 3%–4% rate in 2020–2021 can offer a buyer savings of $500–$1,000+ per month simply by allowing assumption of their loan. The buyer typically pays the seller's accrued equity as a cash payment at closing (the "equity gap"), plus an assumption fee set by the loan servicer.
Which Loan Types Allow Assumption in 2026?
Not all mortgages are assumable. Federal law and HUD guidelines (hud.gov) determine which loan types permit assumption:
- FHA loans — Assumable: All FHA-insured loans originated after December 1, 1986 are assumable with lender approval. The buyer must qualify through standard FHA underwriting. HUD caps the assumption fee at 0.5% of the loan balance (or $900 minimum). The seller can request release of liability once the buyer is approved.
- VA loans — Assumable: VA-guaranteed loans are assumable by both veterans and non-veterans, though a non-veteran assuming a VA loan does not restore the seller's VA entitlement. The VA (va.gov) sets a maximum funding fee of 0.5% for assumptions. The buyer must meet creditworthiness standards set by the loan servicer.
- USDA loans — Assumable: USDA single-family housing loans are assumable with Rural Development approval. The buyer must meet income and property eligibility requirements. USDA charges a guarantee fee on the assumed balance.
- Conventional loans — Usually NOT assumable: Most conventional mortgages backed by Fannie Mae or Freddie Mac contain a "due-on-sale" clause that requires the loan to be paid off when the property is sold. Rare exceptions exist for adjustable-rate mortgages (ARMs) and portfolio loans held by local banks.
Before pursuing an assumption, verify with the loan servicer whether the specific loan is assumable. Request the mortgage note and check for a due-on-sale clause. The servicer must process assumption requests and cannot unreasonably deny them for eligible FHA, VA, or USDA loans.
How to Calculate Remaining Balance (Amortization Math)
The remaining loan balance after any number of payments is calculated using the standard amortization formula. For a loan with principal P, monthly interest rate r, total payments n, and payments already made k, the remaining balance is:
Remaining Balance = P × [(1+r)^n − (1+r)^k] ÷ [(1+r)^n − 1]
This formula accounts for the fact that early payments are mostly interest, so the balance declines slowly at first. For example, a $400,000 loan at 3.25% over 30 years, after 36 payments, has a remaining balance of approximately $375,000 — the principal has only decreased by $25,000 despite 3 years of payments. This calculator applies this exact formula to determine the balance you would assume.
The monthly savings are then computed by comparing: (a) the monthly payment on the assumed balance at the original rate for the remaining term, versus (b) a new loan for the same assumed balance at today's market rate for the same remaining term. The difference is your monthly cash-flow savings from assumption.
The Equity Gap — Cash You Need at Closing
The biggest challenge in mortgage assumptions is the equity gap: the difference between the home's purchase price and the assumed loan balance. If the seller is asking $500,000 for a home with a $375,000 remaining mortgage, the buyer must pay $125,000 in cash (or through a second mortgage) at closing, plus the assumption fee.
Several strategies exist to bridge the equity gap:
- Cash payment: The simplest approach — buyer brings the full equity gap to closing. Works well when the gap is modest relative to buyer savings.
- Second mortgage / piggyback loan: Buyer takes a separate second mortgage to cover part of the equity gap. The combined rate of the assumed first mortgage plus the second mortgage should still be lower than a new first mortgage for this to make financial sense.
- Seller financing: The seller "carries back" part of the equity gap as a promissory note, effectively acting as the second lender. This is negotiable and common in assumption transactions.
- Gift funds: For FHA assumptions, gift funds from family members may be used toward the equity gap, subject to standard FHA gift documentation requirements.
This calculator shows the exact cash needed at closing (equity gap plus assumption fee) so you can plan your financing strategy before making an offer. Sources: hud.gov, cfpb.gov, va.gov. Last updated: May 2026.