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.
Fact-checked by Surrayya Afzal, Principal Broker, FSRA #M14001433· Last reviewed October 2026 · Reviewed monthly
A blend-and-extend mixes your current rate with today's rate and resets you into a new term — so you can lower your rate or lock a new term mid-term. This shows your new blended rate and payment. Compare it against simply breaking and refinancing: when today's rates are much lower than yours, breaking can win even after the penalty.
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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 take the extension rate your lender offers; 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 at an assumed new rate of 4.59% (illustrative rates, not a quote). 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 the 4.59% new rate, with no separate penalty payable to get there. In this example blending is cheaper than breaking because the extension rate is higher than the old rate. Breaking tends to win only when market rates fall well below your contract rate or the lender pads the blend. Compare the written offers and fees.
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 100+ lenders and recommend the genuinely cheaper path — not the one your bank prefers.
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