Finance category

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Blended Mortgage Rate Calculator

The critical number when comparing a cash-out refinance against a HELOC on top of the current mortgage. This calculator produces the blended first + second rate so you can benchmark the refi offer fairly.

First mortgage balance

First mortgage rate

Second / HELOC balance

Second / HELOC rate

Blended rate

7.19%

Combined balance

$375,000

Combined monthly interest

$2,247

First mortgage share

86.67%

Second / HELOC share

13.33%

How the math works

Blended mortgage rate matters when evaluating piggyback loans, cash-out vs HELOC decisions, and consolidation refinances. A $325k first at 6.875% + $50k HELOC at 9.25% blends to about 7.19% — still below a typical cash-out refi that would require refinancing the entire balance.

When deciding between a cash-out refinance and a HELOC, the relevant comparison is not the new cash-out rate vs the old first-mortgage rate — it's the new cash-out rate vs the blended rate of (old first + HELOC).

Editorial noteMaintained by EveryCalc - Reviewed June 2026

EveryCalc calculators are designed for fast, practical estimates with transparent inputs and no required account. We use plain formulas, visible assumptions, and related tools so visitors can check the result from more than one angle.

Results are informational only. For financial, tax, legal, medical, construction, or other high-impact decisions, verify the output against primary sources or a qualified professional.

Learn more about our review process on the EveryCalc methodology page.

How this calculator works

What this page estimates

This Blended Mortgage Rate Calculator is built to give a quick, browser-based estimate for blended mortgage rate. The critical number when comparing a cash-out refinance against a HELOC on top of the current mortgage. This calculator produces the blended first + second rate so you can benchmark the refi offer fairly. The inputs stay on the page during normal use, and the result should be treated as an estimate for planning, comparison, or education rather than professional advice.

Calculation approach

The calculator applies the standard relationship implied by the inputs, then formats the answer so it can be checked and reused. For finance tools, the most important step is using consistent units, rates, time periods, and assumptions before comparing the result with another calculator or outside quote.

Example workflow

For example, start with a realistic value you already know, change one input at a time, and watch how the answer moves. That makes it easier to tell whether the result is being driven by the main amount, the rate, the time period, or a unit conversion.

Practical checks

Use current, real-world numbers when the result affects money, health, tax, or legal decisions.
Run a low, base, and high case when the inputs are estimates.
Check the related calculators below when the next decision depends on a different assumption.

How to interpret the blended mortgage rate result

Best use

Use the result as a planning number for comparing payments, rates, returns, tax reserves, or cash-flow choices before you request a quote or make a commitment.

Cross-check

Compare the answer with the contract, lender estimate, tax form, brokerage statement, payroll record, or invoice that will control the real-world outcome.

Watch for

Do not rely on a single optimistic rate, return, or fee assumption. Money pages work best when you run low, base, and high cases and keep professional advice separate from the estimate.

This page belongs to the Finance calculator library, so the answer should be read in the context of the decision you are modeling rather than as a universal rule.

Before relying on this blended mortgage rate estimate

Most calculator mistakes come from the inputs, not the arithmetic. Use this short audit before you reuse the answer in a spreadsheet, quote, application, or important conversation.

Confirm source numbers

Match balances, rates, fees, taxes, income, and payment dates against the lender quote, payroll record, tax form, statement, invoice, or contract.

Separate cash flow from total cost

A lower monthly payment can still cost more over time if fees, interest, taxes, or a longer term are hidden in the structure.

Run conservative cases

Test at least one higher-cost or lower-return case before using the output for a purchase, refinance, investment, loan, or tax decision.

Rerun this page when the rate, price, term, fee, tax rule, income, expense, or expected holding period changes.

How to Use

Enter first mortgage balance and rate.
Enter HELOC or second mortgage balance and rate.
Read blended rate and the portion split.

Frequently Asked Questions

When should I compare blended rate to a cash-out offer?

Any time you're deciding between adding a HELOC/second vs doing a cash-out refi of the full balance. The refi rate needs to beat the blended rate, not just the current first rate, to make sense.

Does term matter in this comparison?

Yes. A cash-out refi resets to a new 30-year amortization, while the HELOC adds incremental debt without changing the first mortgage schedule. Shortening term on the refi is worth considering in the comparison.

What about tax treatment?

Mortgage interest on the first is deductible up to $750k if used for acquisition/improvement. HELOC interest is deductible only if used to improve the home. Shift the math on effective rate after-tax accordingly.