Type "reverse mortgage calculator" into a search bar and you will get dozens of tools returning different answers for the same house. The spread comes from what each one quietly assumes.
What a real estimate requires
- Age of the youngest borrower or eligible non-borrowing spouse. Not the oldest. FHA's tables are driven by the youngest.
- Appraised home value, capped at the FHA lending limit for a HECM.
- The expected rate — 10-Year CMT plus the lender's margin — not the initial rate.
- Existing mortgage payoff and liens, which come off the top as mandatory obligations.
- Closing costs, including the upfront mortgage insurance premium.
A calculator that only asks for age and home value is showing you a gross principal limit, not money you can actually use.
Principal limit is not cash in hand
The sequence is: home value → Principal Limit Factor → principal limit → subtract closing costs → subtract mortgage payoff and other mandatory obligations → what remains is available to you. On a home with an existing mortgage, that final figure can be a fraction of the headline number.
The first-year 60% rule
FHA limits what you can draw in the first 12 months to 60% of the principal limit, or your mandatory obligations plus 10%, whichever is greater. Any calculator ignoring this will overstate your year-one cash. Ours applies it. Read the detail in mandatory obligations and initial disbursement limits.
Why our calculator differs from most
Our reverse mortgage calculator uses the actual published FHA Principal Limit Factor tables with interpolation between age and rate points, pulls the current 10-Year CMT daily, and nets out an itemized cost estimate. It also runs 5-, 10-, and 15-year projections so you can see the balance trajectory, not just today's snapshot.
Reading the output honestly
- Look at net available proceeds, not principal limit.
- Check the year-one available figure against what you actually need now.
- Look at the projected balance at year 10 against a conservative appreciation assumption.
- If you are choosing a line of credit, note the credit line growth rate — the unused portion grows.
An estimate is not an offer
Every calculator output depends on an appraisal that has not happened yet and a rate that is not locked. Treat it as a planning range. When the number looks workable, request a formal quote and we will run it against a locked expected rate.
