Free estimate based on your property value, lease length and ground rent.
The property type determines which legislation applies.
1993 Act. 90-year extension. Ground rent to peppercorn.
1967 Act. Right to buy freehold at a modest premium.
Enter the freehold value — what the property would sell for with a long or 999-year title.
Enter the unexpired term and current annual ground rent.
Your lease extension premium is the sum of three components, calculated using the same RICS deferment-rate methodology a professional valuer would apply:
Premium = capitalised ground rent + reversion value + marriage value. See our full step-by-step calculation guide and methodology page for the underlying formulas.
Three real calculations using the formula above, shown component by component so you can see exactly where the number comes from:
| Component | Ex. 1: £400k, 75yrs, £150 GR | Ex. 2: £750k, 68yrs, £300 GR |
|---|---|---|
| Capitalised ground rent | £2,923 | £5,783 |
| Reversion value | £412 | £1,766 |
| Marriage value | £4,333 | £16,850 |
| Total premium | £7,667 | £24,400 |
Notice how marriage value dominates the second example — shorter remaining lease terms mean a bigger gap between the short-lease relativity and the near-full relativity 90 years later, which is exactly what the 80-year comparison below illustrates directly.
This is the single most important number on this page. Take the exact same property — £400,000 value, £150 ground rent — and compare it at 75 years remaining versus 85 years remaining:
| Lease length | Marriage value payable? | Total premium |
|---|---|---|
| 75 years (below 80) | Yes — £4,333 | £7,667 |
| 85 years (above 80) | No — £0 | £3,079 |
The only difference between these two rows is 10 years of lease length — yet the premium is 149% higher below the 80-year threshold, purely because marriage value kicks in. See our full 80-year rule guide for why this cliff-edge exists and when to act before you cross it.
The premium itself is only part of the total cost. UK law requires you to pay your own professional costs and the freeholder's reasonable professional costs:
Budget roughly £2,200–4,500 in professional costs on top of whatever premium this calculator estimates. See our full solicitor fees breakdown for a complete cost picture.
This calculator uses the RICS methodology currently in force. Here's exactly where reform stands as of this writing:
See our full 2024 Act guide and should I wait or extend now? analysis for the complete picture, including the Court of Appeal risk in detail.
This calculator uses the official RICS deferment rate methodology and should be within 10–20% of a professional valuation for most straightforward properties. Actual premiums depend on local comparable evidence that only a registered surveyor can access, so always get a formal valuation before serving a Section 42 notice or agreeing a figure with your freeholder.
Nothing — they're the same thing. "Lease extension" and "leasehold extension" are used interchangeably to describe the same statutory process of extending a long residential lease under UK law, and this calculator covers both.
This calculator uses the RICS methodology currently in force. The Leasehold and Freehold Reform Act 2024 already provides for abolishing marriage value and extending leases to 990 years, but as of this writing only around 10 of its 125 sections have been commenced, and there's no confirmed date for the rest. We'll update this calculator the moment any relevant provision actually takes effect.
You'll need your property's current market value, the exact number of years remaining on your lease (check your lease document or ask your solicitor), and your current annual ground rent, including whether it's fixed, doubles periodically, or is linked to RPI.
No. This calculator gives a genuinely useful estimate to budget with and sanity-check a figure you've been quoted, but it can't access the local comparable evidence a RICS surveyor uses for a formal valuation. Treat the result as a strong starting point, not a final number to negotiate or litigate with.
This calculator's methodology is reviewed by James Norton MRICS, a Chartered Surveyor and Registered Valuer, against current RICS guidance and reported tribunal determinations. Legal and process content is reviewed by Sarah Mitcham, a property solicitor. See our full calculator methodology and editorial policy.