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Lease Extension & Freehold Calculator 2026

Estimate the premium to extend your lease or buy the freehold — including the marriage value that bites once your lease falls below 80 years.

Your Lease Details

Enter your flat's value, the years left, and the ground rent

The Property

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yrs
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Surveyor Assumptions (advanced)

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Your lease extension estimate

Enter your lease details and click Estimate Premium to see the likely cost of extending your lease or buying the freehold.

Estimated Premium

£300,000 flat, 75 years remaining
Estimated Premium
—
to the freeholder
Premium + Fees
—
total cost
ComponentEstimated value

This is an illustrative estimate only — not a valuation or legal advice. Lease extension premiums are negotiated and depend on a professional valuation. Always instruct a RICS surveyor and a specialist solicitor before serving notice. See our Disclaimer.

Extending Your Lease: What It Costs and Why the Clock Matters

If you own a leasehold flat, there's a number quietly working against you: the years left on your lease. Every year that ticks down, your flat is worth a little less and the cost to put it right goes up. And there's one threshold — 80 years — where the maths turns genuinely nasty. This calculator estimates what you'd pay to extend, and the guide below explains where that figure comes from.

How the Premium Is Calculated

The premium you pay the freeholder is built from three parts:

  • Capitalised ground rent. When you extend, your ground rent drops to a peppercorn (effectively zero). The freeholder is compensated for the income they lose, valued in today's money over your remaining term.
  • Reversion. At the end of the lease the flat would return to the freeholder. Extending pushes that decades into the future, so they're paid for the value of that lost "reversion", discounted to today.
  • Marriage value (only below 80 years). Extending makes the flat worth more. Below 80 years the law makes you hand the freeholder half of that uplift. Above 80 years, marriage value is legally zero.
The 80-year trap. Marriage value is why advisers shout about the 80-year mark. On a £300,000 flat, the difference between extending at 81 years and waiting until 79 can be thousands of pounds — for the sake of doing nothing. If your lease is anywhere near 85 years, get moving: the application itself can take months, and it's the date you serve notice that counts.

A Worked Example

Take a £300,000 flat with 75 years left and £250/year ground rent, using typical rates (6% capitalisation, 5% deferment):

  • Capitalised ground rent: ~£4,100
  • Reversion: ~£7,700
  • Marriage value: ~£1,600
  • Estimated premium: ~£13,400, plus £2,000–£4,000 in combined legal and valuation fees.

Drop the same flat to 60 years and the premium climbs to around £28,000 as marriage value and the reversion both grow. That's the cost of delay in one line.

Reform is coming — but isn't here yet. The Leasehold and Freehold Reform Act 2024 will abolish marriage value and extend new lease terms to 990 years. As of 2026, however, those valuation changes are not yet in force — the government is still consulting on the rates, with implementation expected late 2026 at the earliest. Until then, the traditional calculation above (including marriage value below 80 years) still applies. If your lease is comfortably above 80 years, it may be worth watching the reform; if it's near or below 80, waiting is a gamble.

Buying the Freehold (Houses and Flats)

Buying your freehold uses the same building blocks. For a house, you buy out the freeholder's interest directly (capitalised ground rent + reversion, plus marriage value if the lease is short). For a flat, buying the freehold means collective enfranchisement — you and the other leaseholders club together to buy the building's freehold, and each flat's share is valued on the same basis. The premium per flat is broadly comparable to a lease extension; the difference is you also gain control of the building.

Fees You'll Also Pay

  • Your valuation: £400–£800 for a RICS lease extension valuation.
  • Your legal fees: £1,000–£2,000 for a specialist solicitor.
  • The freeholder's reasonable costs: on a statutory claim you also pay their valuation and legal fees — budget another £1,000–£2,000.

Frequently Asked Questions

How much does it cost to extend a lease in the UK?
It depends on the flat's value, years remaining and ground rent. A £300,000 flat with 75 years left and £250 ground rent might cost around £13,000–£14,000 in premium, plus £2,000–£4,000 in combined fees. Below 80 years the premium rises sharply because of marriage value. Use the calculator above for your figures, then get a RICS valuation.
What is the 80-year rule for lease extensions?
Once a lease falls below 80 years, you must pay marriage value — 50% of the uplift the extension creates — on top of the other components. The cost keeps climbing the shorter the lease gets, so leaseholders are usually advised to extend before hitting 80 years. The date that counts is when you serve formal notice, not when you start the process.
What is marriage value in a lease extension?
It's the increase in the combined value of the lease and freehold created by extending. The law currently splits it 50/50 between leaseholder and freeholder, but only on leases under 80 years. The Leasehold and Freehold Reform Act 2024 will abolish marriage value — but that change is not yet in force as of 2026.
Is it cheaper to extend my lease now or wait for the reforms?
It depends on your lease length. The reforms (which will abolish marriage value) are not in force as of 2026 and have no confirmed date. If your lease is well above 80 years, waiting carries little risk and could save money. If it's near or below 80 years, every year of delay adds marriage value now — and the reform might not arrive before you'd be forced to act. Take advice on your specific lease.
How accurate is this lease extension estimate?
It's a guide, not a valuation. Real premiums depend on the precise capitalisation and deferment rates a surveyor applies, the "relativity" used for marriage value (which is contested), and negotiation. Treat the result as a ballpark to budget around, and always commission a RICS lease extension valuation before serving notice.