Blend-and-extend mortgage calculator.
Blend-and-extend lets you lock a longer term early by blending your existing rate with today's rate — with no prepayment penalty. See your blended rate and payment, then weigh it against breaking your mortgage and paying the IRD.
Your inputs
Lender-ready summary, your assumptions baked in, and a personalized note from an advisor at Mortgage Squad Advisors.
Blend, break, or stay?
Blend-and-extend exists to solve one problem: you want to change your rate or lock a longer term before your current term ends, but you don’t want to pay a prepayment penalty to do it. The lender blends your existing rate with today’s rate and you sign a new, longer term at that average — and because you never technically break the mortgage, there’s no Interest Rate Differential to pay.
How the blended rate is built
It’s a time-weighted average. The months remaining on your current term keep your old rate; the additional months of the extension take today’s rate; the blend is the weighted average across the whole new term. So the more time left on your current (cheaper) rate, the lower the blend — and the longer the extension you add at today’s rate, the more the blend drifts toward current pricing. The calculator shows the exact blended rate for your inputs.
A worked example: $450,000 with 20 months left
Say you’re at 2.79% with 20 months left on a $450,000 balance, and you blend into a new 5-year (60-month) term where today’s rate is 4.59%. Twenty months keep the 2.79%; the other 40 months take 4.59%. The blended rate is (2.79 × 20 + 4.59 × 40) ÷ 60 ≈ 3.99% — below today’s 4.59%, with no penalty to get there. The catch: a clean break-and-switch to a sharp 4.59% might still beat 3.99%-for-five-years once you do the full-term math, or the lender may quote a blend above this fair number. That’s why you compare, never assume.
The honest caveat
Lenders set the blended rate, and they don’t always set it generously. A padded blend can quietly cost more than breaking the mortgage and switching to a sharply discounted new rate, even after the penalty. So the right move is always to compare all three paths on real numbers: the blended rate here, the cost to break in the penalty calculator, and the savings from a clean switch in the refinance calculator. We run that comparison across 50+ lenders and recommend the genuinely cheaper path — not the one your bank prefers.