Assumable Mortgage Calculator
Calculate your monthly payment and savings when assuming a seller's below-market mortgage. See the cash needed at closing and compare to buying at current rates.
$
$
%
yrs
$
%
Payment on Assumed Loan
$1,602
vs. $2,854/mo on a new 6.8%, 30-yr loan
Assumed Rate
3.3%
Market Rate
6.8%
Cash Needed at Closing
$230,000
LTV on Assumed Loan
58.2%
Monthly Savings vs New Loan
$1,252
Interest Savings vs New Loan
$446,106
High cash requirement ($230,000). Consider a second mortgage (HELOC or second lien) to bridge the gap.
Advanced
Advanced Calculator
Rate savings comparison, cash gap strategies (second mortgage, personal loan)
Your rate savings: 3.3% assumed vs 6.8% market (3.5% differential) on $320,000 balance.
Assume Seller's Loan
$1,602/mo
3.3% rate · 24-yr remaining
Total interest: $141,274
Cash needed: $230,000
New 30-Year Loan (20% Down)
$2,854/mo
6.8% rate · 30-yr
Total interest: $587,379
Down payment: $110,000
Monthly Payment Savings
$1,252
Assumed vs new loan
Total Interest Savings
$446,106
Lifetime interest difference
Annual Savings
$15,026
Monthly savings × 12
5-Year Savings
$75,131
Monthly savings over 5 years
Rate Advantage
3.5%
Lower rate on assumed loan
Cash Gap
$230,000
Needed at closing
Pro
Professional Simulator
Qualification analysis, blended rate calculator, credit score impact
$
$
pts
Monthly Income
$10,000
Max DTI Allowed
43%
Most lenders
Max Housing Payment
$3,800
43% DTI minus existing debts
DTI with Assumption
43.7%
Assumed + 2nd mortgage payment
DTI with New Loan
33.5%
New 30-year loan
Can Qualify (Assumption)
Tight
Credit Score
740
Good
Credit Rate Adjustment
+0.3%
Added to market rate
Your New Loan Rate
7.0%
Market + credit adjustment
Your New Loan Payment
$2,927
With credit-adjusted rate
Your DTI with the assumption (43.7%) exceeds the 43% guideline. Consider: a larger down payment to reduce second mortgage size, paying off existing debts first, or a co-borrower.
How to Use This Assumable Mortgage Calculator
Enter the seller's Original Loan Amount, Current Balance (what you'd assume), and their Original Rate and Years Remaining. Then enter the Home Sale Price and today's Market Rate to compare against taking out a new loan at current rates.
The calculator shows your assumed payment, the cash you'll need at closing (purchase price minus assumed balance), and how much you'd save monthly and over the remaining loan life compared to a new market-rate loan.
Assumable Mortgage Math
Assumed Payment = Monthly Payment(Balance, Seller's Rate, Remaining Term)
Cash Needed = Sale Price − Current Balance (assumed)
LTV on Assumed Loan = Current Balance ÷ Sale Price
New Loan Alternative (for comparison):
New Down Payment = Sale Price × 20%
New Loan = Sale Price × 80%
Monthly Savings = New Payment(Market Rate) − Assumed Payment
Lifetime Interest Savings = Total Interest(New Loan) − Total Interest(Assumed)
Cash Needed = Sale Price − Current Balance (assumed)
LTV on Assumed Loan = Current Balance ÷ Sale Price
New Loan Alternative (for comparison):
New Down Payment = Sale Price × 20%
New Loan = Sale Price × 80%
Monthly Savings = New Payment(Market Rate) − Assumed Payment
Lifetime Interest Savings = Total Interest(New Loan) − Total Interest(Assumed)
Example: Assuming a 3.25% FHA Loan
$550,000 Home — Assuming Seller's Low-Rate Mortgage
| Seller's Rate | 3.25% |
| Balance to Assume | $320,000 |
| Years Remaining | 24 |
| Assumed Monthly Payment | $1,727 |
| Cash Needed at Closing | $230,000 (gap) |
| Market Rate (comparison) | 6.75% |
| New 30-yr Payment at Market | $2,862 (80% LTV) |
| Monthly Savings vs New Loan | $1,135/month |
| Lifetime Interest Savings | ~$285,000 |
The payment savings are dramatic — but the $230,000 cash gap is the challenge. Buyers often need a second mortgage or bridge loan to cover this gap, which partially offsets the rate advantage.
Frequently Asked Questions
An assumable mortgage lets a buyer take over the seller's existing loan — including the original interest rate, remaining balance, and loan terms. This is particularly valuable when the seller has a rate significantly below current market rates, as the buyer inherits that lower rate for the remainder of the loan.
FHA, VA, and USDA loans are assumable with lender approval. Conventional loans (Fannie Mae, Freddie Mac) are generally not assumable — they have due-on-sale clauses requiring full repayment when ownership transfers. Most mortgages originated in 2020–2022 at low rates are FHA or VA, making this most relevant for those loan types.
The cash gap between the assumed balance and the purchase price. If a home sells for $550,000 but the assumed balance is $320,000, you need $230,000 in cash (or a second mortgage) at closing. This is the primary barrier — many buyers can't cover a gap this large, limiting who can take advantage of assumable mortgages.
VA loans can be assumed by non-veterans, but doing so ties up the veteran seller's VA entitlement until the loan is fully paid off. This means the veteran can't use that entitlement for a new VA loan until the assumed loan is satisfied — unless the assuming buyer is also a veteran who substitutes their entitlement.
FHA assumptions typically take 45–90 days because the lender must approve the buyer's creditworthiness. VA assumptions can take 3–6 months due to additional documentation. This is longer than a standard home purchase (30–45 days), so plan accordingly when making offers with assumption contingencies.