Blended Mortgage Calculator

Assumable first lien + gap financing

Blended Mortgage Calculator

Model a purchase where the buyer assumes the seller's existing first mortgage and covers the equity gap with cash plus a second lien. Compare the blended payment against a new loan at today's rate.

Enter your own numbers. Nothing is pre-filled, and every result is an estimate for discussion, not a loan offer.

Listing

Purchase price

Buyer cash toward equity

Assumable first mortgage

From the listing: rate, balance, and monthly payment. Confirm with the servicer before writing an offer.

Loan type

Interest rate

Unpaid principal balance

Listed P&I (optional)

Cross-check against the term

Time left on the loan

Payments remaining until payoff. Origination date + original term, or the servicer's statement.

Annual MIP / MI

Carries over with the loan

Assumption transaction fee

Upfront

Due at servicer's Clear to Close

VA funding fee

Of assumed balance; confirm exemption status

Second lien (gap financing)

Covers whatever part of the equity gap the buyer's cash doesn't. Amount is calculated.

Interest rate

Term

Interest-only period

0 for fully amortizing

Second-lien closing costs

Carrying costs

Property taxes

Per year

Homeowners insurance

Per year

HOA dues

Per month

Compare: new loan

Same price, same buyer cash, one new first mortgage.

Market rate

Enter a lender quote.

Term

PMI above 80% LTV

Annual, on loan balance

New-loan closing costs

Enter your numbers to see results

Add the purchase price, the assumable loan's rate, balance and time left, and a market rate for the new-loan comparison. If the buyer's cash doesn't cover the equity gap, add the second lien's rate and term.

Blended rate–

Blended PITI–

vs. new loan–

Capital stack

Layer	Amount	% of price	Rate	Term left

Monthly payment

First payment month. Taxes, insurance and HOA are the same in both columns.

	Assume + 2nd	New loan

Lifetime savings

The assumed loan has fewer than 30 years left, so it pays off sooner and carries less total interest than a new 30-year loan.

Interest saved–

Debt-free–

Total cost saved–Interest + insurance + fees

	Assume + 2nd	New loan	Difference

Cost over a holding period

What each structure costs if the buyer sells or refinances at the end of the period. Borrowing cost = interest + mortgage insurance + closing costs.

	Assume + 2nd	New loan	Difference

Cash to close

	Assume + 2nd	New loan

How the numbers work. Blended rate is the balance-weighted average of the two note rates. Cash-flow rate is the monthly yield that equates combined loan proceeds with every scheduled payment on both liens, so it reflects each loan's term. Payment-equivalent rate is the rate a single new loan of the same term would need to produce the same starting P&I on the combined balance.

Modeling assumptions. MIP/MI on the assumed loan is charged monthly on the current balance until payoff. Lifetime figures run every scheduled payment to payoff with no prepayment or refinance. PMI on the new loan drops when the scheduled balance reaches 78% of the purchase price. Prepaids, escrow reserves, lender credits and seller concessions are excluded. Recording, title and transfer taxes are the same for both structures and are left out of cash to close.

Estimates only. Listing-portal rate and balance figures are estimates. Get a payoff/assumption statement from the servicer and a written second-lien quote before relying on these results.

PMMSDATA|7.40|6.71|Oct 15, 2026