RIO Mortgage Calculator — See the Payment That Never Grows

A retirement interest-only mortgage — RIO — lets you borrow against your home and pay back only the interest, every month, for as long as you own the property. There's no fixed term the way there is with a standard 25-year mortgage; it continues until you die, move into permanent long-term care, or choose to sell.

This calculator does two things at once: it shows your actual monthly payment, and it puts that flat, unchanging balance next to what the same debt would become if it compounded instead — which is exactly what happens with equity release. Our fuller guide to RIO mortgages explained covers the product itself in depth; this page is the numbers.

RIO mortgages carry lower LTV caps than a standard residential mortgage, reflecting the specialist, later-life nature of the product. Most UK lenders cap borrowing somewhere between 50% and 65% of your property's value — noticeably below the 85-90% you might see on a typical first-time-buyer mortgage.

Beyond the LTV cap, your actual maximum also depends on whether your retirement income — pension, annuity, rental income, investment income — can sustainably cover the monthly interest payment, tested by the lender at application.

Compare that against equity release, where 2026 rates typically sit between 6% and 8.3% MER. RIO mortgages are usually cheaper on the headline rate too — and the difference in how the balance behaves is even larger, covered next.

The trade-off is genuinely simple: a RIO mortgage costs you a real, ongoing monthly payment. Equity release costs nothing monthly but considerably more over the life of the loan. If your retirement income can comfortably cover the monthly interest, the numbers tilt heavily toward the RIO mortgage — our guide to RIO mortgages explained walks through this trade-off with more worked examples.

Most UK lenders set a minimum age of 55, though some go as low as 50. There's genuinely no maximum age at the other end — some lenders will lend well into your 80s, provided your retirement income comfortably covers the monthly interest indefinitely, since there's no fixed end date to plan around. Every retirement interest only mortgage calculator worth using should reflect this age-banded LTV structure, which is exactly what this one does.

Affordability is assessed almost entirely on retirement income sources — state pension, private pension, annuity income, rental income — rather than employment income, even if you're still working part-time.

You're 68, your home is worth £350,000, and you want to borrow £140,000 — a 40% LTV, comfortably inside typical lender limits. At 5.5%, your monthly interest payment is roughly £642.

Twenty years later, at 88, you still owe exactly £140,000 — not a penny more, because you've been paying the interest the whole way through. The same £140,000, left to compound as an equity release lifetime mortgage at 6.5% with no payments, would have grown to roughly £490,000 over the same 20 years.

That's a genuine £350,000 difference in what's ultimately owed — the real, tangible cost of choosing to service the interest rather than letting it roll up.

Official sources & further reading: read general guidance at MoneyHelper, and verify any lender or adviser on the FCA register. Read our full guide to RIO mortgages, or compare against equity release with our equity release calculator.