Reverse Mortgage Line of Credit Calculator

Same Numbers, Two Meanings: Debt Owed vs. Credit Available

It's worth pausing on this before anything else, because it trips people up more than any other part of a HECM. If you draw $120,000 from a reverse mortgage and never pay it down, the calculator shows that $120,000 compounding into a larger and larger balance owed— that's debt, and it reduces the equity left in the home. But if you instead open a line of credit for $120,000 and draw nothing at all, the exact same compounding math shows that $120,000 growing into a larger and larger amount you're allowed to borrow— that's available capacity, and until you actually draw against it, no debt exists and no equity has been spent.

The formula doesn't know or care which interpretation applies; it just compounds a rate against a number every month. What determines whether that growing number is a liability or an asset-in-waiting is simply whether the money has been withdrawn yet. That distinction is the entire reason a HECM line of credit is treated as a standalone planning tool rather than just a slower way to take a lump sum.

How the Undrawn Portion of a Line of Credit Grows

Per the Consumer Financial Protection Bureau, "whatever you don't use in your credit line will keep growing, allowing you to borrow up to a maximum amount stated in your mortgage." The rate that growth compounds at is the same rate used elsewhere in a HECM: your loan's note rate plus the ongoing mortgage insurance premium, applied monthly and compounded — not simple interest, and not tied in any way to your home's appraised value. Only the unused portion of the line grows this way; once you draw an amount, it stops contributing to future growth and instead becomes part of your outstanding balance, accruing interest as debt from that point forward.

Because the rate is monthly compounding, growth accelerates the longer a line sits untouched — the same acceleration our reverse mortgage calculator page describes for a growing balance owed, just working in your favor here instead.

Why This Isn't the Same as a HELOC

A home equity line of credit looks superficially similar — draw what you need, pay interest only on what's drawn — but the two products behave very differently once you look at what happens to the unused portion, and what a lender can do to it:

The growth feature and the FHA-backed protection against reduction are the two pieces that make a HECM line of credit fundamentally different from a HELOC, not just a slower-moving version of the same product.

Worked Example: Undrawn Credit Growth Over 10 and 20 Years

Take a borrower who opens a HECM with a $120,000 line of credit against their home and draws nothing from it. Their combined growth rate is a 5.75% note rate plus 0.5% ongoing MIP — 6.25% compounding monthly. Here's what the untouched, available line looks like over time:

At this combined rate, the rule of 72 (72 ÷ 6.25) suggests the line should roughly double in a little over 11 years if left completely untouched — and running the actual monthly compounding confirms it, with the balance surpassing double the original $120,000 by year 12. None of this $297,485 in growth by year 20 is money owed; it's simply how much more this borrower could choose to draw at that point than they could on day one, with zero interest accrued because nothing was withdrawn.

Strategic Uses for a Growing Line of Credit

Delaying Social Security

Some retirees draw living expenses from a HECM line of credit for a few years specifically to put off claiming Social Security, since benefits increase through delayed retirement credits for every year claiming is postponed up to age 70. The CFPB has examined this strategy directly and cautions that for many borrowers, the interest, mortgage insurance, and fees that accrue on whatever is actually drawn can end up costing more than the extra lifetime Social Security income gained — the bureau generally found that homeowners relying mainly on their home and Social Security are often better off simply claiming benefits rather than borrowing to delay. This approach tends to make more sense for borrowers with substantial home equity relative to their needs, who plan to stay in the home long term, and who've run the actual numbers rather than assumed the strategy pays for itself.

A Standby Emergency Fund That Grows

Others open a line of credit specifically to leave it alone — a reserve set aside for a medical expense, a home repair, or a period when investment markets are down and they'd rather not sell assets at a loss. Because the undrawn line keeps growing regardless of market conditions, it functions as a standby buffer that gets larger the longer it goes unused, unlike a cash reserve sitting in a low-interest savings account. Financial planners sometimes describe this as using home equity to reduce the risk of having to sell investments during a downturn, rather than as a source of everyday spending money.

Risks and Considerations

A growing credit line isn't free money, and it isn't without conditions:

• The loan can still become due.While a lender can't reduce or freeze your line because home values fall or markets shift, the loan itself becomes due — a "maturity event" — if you stop occupying the home as your primary residence, fall behind on property taxes or homeowners insurance, or fail to maintain the property. Any of those ends your access to the line, growth and all.
• A portion may be set aside and unavailable to draw freely.If a lender's required financial assessment finds a borrower's income or credit history doesn't clearly support paying ongoing property taxes and insurance, HUD rules can require setting aside part of the proceeds specifically to cover those costs, which reduces how much of the line is available for discretionary use even though it's still part of the loan.
• Upfront costs still apply. Opening any HECM — whether you plan to draw immediately or leave it untouched to grow — carries the same upfront mortgage insurance premium, origination fee, and closing costs as a standard reverse mortgage. Those costs are worth weighing against the value of the growth feature itself, not just against cash you might have drawn.
• It's still a lien against your home.You retain ownership, but the growing line of credit represents equity the lender is prepared to lend against, not equity that's risk-free to leave outstanding indefinitely — it still reduces what's left for you or your heirs if it's ever drawn down.

Methodology and Sources

The calculator above compounds your entered rate plus ongoing MIP monthly against a starting balance — identical to the growth model on our reverse mortgage calculator, since a HECM uses the same combined rate to grow a drawn balance as debt and an undrawn line as available credit. The worked example above uses that same formula at a 5.75% note rate plus 0.5% MIP. Payment-option details, including the line-of-credit growth feature and the ability to combine a line of credit with monthly payments or a lump sum, come from the CFPB's guidance on reverse mortgage payment options, and general HECM eligibility and borrower-responsibility rules come from the CFPB's reverse mortgage basics guidance. If you're instead planning to draw a lump sum right away, see our standard reverse mortgage calculator and reverse mortgage purchase calculator if you're financing a new home purchase instead of tapping equity you already have. For the math behind a normal, amortizing loan that shrinks toward zero instead of growing — like the one most homeowners under 62 are paying down — see our standard mortgage amortization calculator or our standard amortization methodology page.