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Key takeaways
- Assuming a loan means taking over the seller’s rate and balance, but you must pay the difference between the price and that balance.
- In the default example, a $400,000 home with a $280,000 loan at 3% has a $120,000 equity gap.
- Paying that gap with $20,000 cash and a $100,000 second loan at 8.5% still gives a payment $123.57 a month lower than a new 6.5% loan, and about $66,942 lower total cost over 7 years.
- The saving comes mostly from the low-rate balance, not from a big monthly difference, so test the second loan rate carefully.
What this assumable mortgage calculator does
It compares two ways to buy the same home. In the first you assume the seller’s existing loan and cover the equity gap with your cash plus, if needed, a second loan. In the second you take a new loan at today’s rate. The calculator shows the equity gap, the second loan you would need, the payment on each route, the cash needed at closing, and the total cost over the number of years you plan to own the home.
How the equity gap works
The assumed loan replaces only what the seller still owes. If the home costs more than that balance, you owe the seller the difference at closing. That gap is paid with cash, a second loan, or both. A large gap is the main reason an assumption can be less attractive than the low headline rate suggests. Use the affordability calculator to check that the cash and the combined payment fit your budget.
How it is calculated
Each loan’s payment is the standard fixed-rate payment M = L × r × (1 + r)n ÷ ((1 + r)n − 1). The assumed loan uses its remaining balance, its rate and the years left. The total cost over your holding period adds the payments made, the balance still owed on every loan at the end, and the cash paid at closing. The loan with the lower total is cheaper for that time frame. The calculator shows the full working under “show the math”.
Worked example: $400,000 home, 7 years
| Assume the loan | New loan | |
|---|---|---|
| Loans | $280,000 at 3.00%, 26 years left, plus $100,000 at 8.50%, 15 years | $380,000 at 6.50%, 30 years |
| Monthly principal & interest | $1,293.55 + $984.74 = $2,278.29 | $2,401.86 |
| Cash at closing | $23,500 ($20,000 plus $3,500 fees) | $29,500 ($20,000 plus 2.5% closing costs) |
| Balance owed after 7 years | $293,019 ($224,597 + $68,422) | $343,582 |
| Total cost over 7 years | $507,895 | $574,838 |
The assumed route is about $66,942 cheaper over seven years, even though the monthly payment is only $123.57 lower. Most of the saving is in the balance: at 3% less of each payment goes to interest, so you owe about $50,000 less after seven years. The second loan at 8.50% eats part of the benefit. The rates and fees here are illustrations, not quotes.
What can go wrong
The loan may not be assumable
Many conventional loans have a due-on-sale clause. FHA, VA and USDA loans are the usual candidates. Ask the servicer, and ask whether the seller can be released from liability.
You still have to qualify
The servicer will generally review your credit and income, and the process can take longer than a normal purchase loan. Build that into your contract dates.
The loan keeps its original terms
That includes any mortgage insurance and the remaining years, so a loan with 26 years left ends in 26 years, not 30. See the main mortgage calculator for taxes, insurance and PMI on top, and the refinance calculator if you might refinance later.
The second loan can be expensive or unavailable
Rates and rules vary, and some loans restrict additional liens. Get a real quote before you rely on one.
Estimate only, for principal and interest. It leaves out taxes, insurance, mortgage insurance and other costs. Rules, fees and approval depend on the loan type and servicer. Not a loan offer or financial advice.
Frequently asked questions
What is an assumable mortgage?
An assumable mortgage lets a buyer take over the seller’s existing loan, keeping its rate, remaining term and balance, instead of getting a new loan. The lender or servicer must approve the buyer first.
Which loans can be assumed?
FHA, VA and USDA loans can generally be assumed with lender approval. Most conventional loans contain a due-on-sale clause that prevents it, though there are exceptions such as some adjustable-rate loans. Check the seller’s loan documents or ask the servicer.
What is the equity gap?
It is the difference between the home’s price and the balance of the loan you are assuming. If a home sells for $400,000 and the loan balance is $280,000, the gap is $120,000. You must cover it with cash, a second loan, or a mix of both, because the assumed loan only replaces the seller’s balance.
Do I need to qualify to assume a loan?
Usually yes. For FHA, VA and USDA loans the servicer reviews your credit, income and debts much as it would for a new loan. The process often takes longer than a new purchase loan, so ask for the timeline early.
What happens to the seller on a VA loan?
The seller’s VA entitlement can stay tied to the assumed loan unless the buyer is an eligible veteran who substitutes their own entitlement. Sellers should ask for a release of liability. VA also charges a funding fee on assumptions, so confirm the current amount.
Can I use a second mortgage for the equity gap?
Often, but not always. Some servicers or loan types limit extra liens, and second loans usually carry a higher rate than first mortgages. Enter your quoted second-loan rate in the calculator so the blended cost is realistic.
Is assuming always cheaper than a new loan?
No. It depends on how low the old rate is, how big the equity gap is, and what a second loan costs. With a large gap financed at a high second-loan rate, the advantage can shrink or disappear. Change the inputs to test your own case.