Lease Extension Calculator — Estimate Your Premium (2026)

Estimate what a statutory lease extension would cost under the Leasehold Reform, Housing and Urban Development Act 1993. Enter three figures — years remaining, the flat's long-lease value, and your ground rent — and this calculator returns a likely premium RANGE (a surveyor never quotes a single number, so neither do we), shows whether the 80-year marriage-value cliff applies, and lets you check the building's tribunal dispute history before you serve notice. Instant, no email wall.

Value after extending / with share of freehold

Typical ground rent: ~£304 mean / £120 median (EHS).

Instant estimate. Statutory LRHUDA 1993 method — an estimate, not a RICS valuation.

Instant tool. The full property report is £9.99 Lite / £24.99 Complete — one report, one price, no subscription.

How this lease extension calculator works

Enter your unexpired lease years, the flat's value with a long lease (or share of freehold), and your annual ground rent. The tool applies the statutory valuation under Schedule 13 of the Leasehold Reform, Housing and Urban Development Act 1993 (LRHUDA 1993) and returns a premium as a low–central–high range. Every top lease-extension calculator on the web shows a single number; a surveyor never would, because the answer turns on negotiated relativity and the exact lease terms. We show the range, the marriage-value treatment, and the assumptions behind every figure.

Your result explained

The premium is built from three parts. Term loss is the ground rent the freeholder gives up, capitalised at roughly 7%. Reversion loss is the value of the freeholder eventually getting the flat back, deferred to today at the 5% Sportelli deferment rate. Marriage value is half the value created by extending — and it is added only when the lease is below 80 years. If your lease is above 80 years the result will say so and exclude marriage value; if it is below, the marriage-value line lights up red, because that is the number that grows the longer you wait.

The 80-year cliff — why every year counts

The single most important fact in lease extension is the 80-year cliff. At 80 years and above, marriage value is deemed nil. The moment the lease falls below 80 years, you must pay the freeholder 50% of the value uplift, and that figure rises steeply as the term shortens. The calculator draws this as a premium-versus-years curve with your position marked, so you can see exactly how much a delay costs.

Unexpired term£200,000 flat (no ground rent)£500,000 flat (no ground rent)
90 years~£3,000–£5,000~£7,000–£12,000
82 years~£6,000–£9,000~£14,000–£22,000
79 years (just below cliff)~£9,000–£14,000~£22,000–£34,000
70 years~£14,000–£22,000~£34,000–£55,000

Illustrative ranges from the calculator's own method (deferment 5%, ground-rent yield 7%, graph relativity); your figure depends on ground rent and the negotiated relativity. An estimate, not a valuation.

What this means for your purchase

If you are buying a flat, a short lease is both a cost and a negotiating lever: the premium you'll pay to extend should come off your offer. A lease under 80 years also narrows the pool of lenders willing to mortgage it. Work out the likely premium here, then read whether the lease is short enough to walk away from in our guide to whether a lease is too short to buy — and run a HouseCheckup Snapshot on the address to see the wider picture.

Check this building's dispute history before you extend

A freeholder or managing agent with a history of First-tier Tribunal (Property Chamber) disputes can be harder to negotiate a lease extension with — and the same building often shows up across service-charge and management cases. HouseCheckup holds 16,880 published tribunal decisions keyed to postcode and building, something no other lease-extension calculator links to. Before you serve a Section 42 notice, check whether your building has a tribunal dispute history.

Is there an official government lease extension calculator?

No — there is no lease-extension calculator on gov.uk. The widely-cited free tool belongs to LEASE (lease-advice.org), a government-funded charity, not a government service. Northern Ireland publishes an Excel template for its own (different) scheme. So while many searchers look for a "government" or "gov" calculator, none exists; treat every online estimate — including this one — as a guide and confirm with a RICS valuation.

Land Registry & registration fees

Beyond the premium and professional fees, the extended lease must be registered at HM Land Registry, which charges a scale fee based on the property value (commonly £20–£150 for a registered title under the standard scale). Your solicitor handles this as part of completion. See our buying costs calculator for how registration and legal fees fit the wider cost of a purchase.

How the process works (Section 42 to tribunal)

The statutory route: own the flat for two years, obtain a RICS valuation, serve a Section 42 notice on the freeholder proposing a premium, then negotiate. If you can't agree within the statutory window, either side can apply to the First-tier Tribunal to determine the premium — a process that adds a few months. Most cases settle by negotiation; the published tribunal decisions exist precisely because some don't, which is why a freeholder's dispute history is worth knowing.

The law is changing — Leasehold and Freehold Reform Act 2024

The Leasehold and Freehold Reform Act 2024 will, once commenced, abolish marriage value, standardise the valuation rates, and let leaseholders take a 990-year extension at a peppercorn rent — materially cheaper for most. However, the key valuation provisions are not yet in force and, given the secondary legislation and consultation still required, are unlikely to commence before 2027. Until then, the LRHUDA 1993 method this calculator uses remains the law. We will update the engine when the new rules take effect.

Get the full picture for the address

Lease length is one factor among many. The HouseCheckup Complete report pulls the leasehold context — alongside true running costs, flood, EPC, crime and 70+ other checks — for a specific address, so you go into the purchase or the extension knowing exactly what you're taking on. This estimate is an estimate, not a RICS valuation — instruct a surveyor before serving notice.

Frequently asked questions

It depends on the flat's value, the unexpired lease length and the ground rent. A flat worth £300,000 with just over 80 years left might run to roughly £8,000–£15,000 of premium; once the lease falls below 80 years, marriage value (50% of the value uplift) is added and the figure climbs steeply. On top of the premium, budget £3,000–£5,000 of professional fees. This calculator returns a low–central–high range rather than a single false-precise number.
When a lease drops below 80 years, the statutory formula adds 'marriage value' — the increase in value created by extending — and you must pay the freeholder 50% of it on top of the basic premium. This is the '80-year cliff': the premium jumps as the lease crosses 80 years and keeps rising the shorter it gets. Extending before 80 years is almost always cheaper.
No. There is no calculator on gov.uk. The most-cited free tool is run by LEASE (lease-advice.org), a government-funded charity, not a gov.uk service. Northern Ireland publishes a spreadsheet for its own scheme, but that is NI-only and uses different rules. Any 'gov' lease-extension calculator you find online is a third party's, so always treat the output as an estimate and instruct a RICS surveyor before serving a Section 42 notice.
Under LRHUDA 1993 Schedule 13 the premium has up to three parts: the term loss (the ground rent the freeholder gives up, capitalised), the reversion loss (the value of getting the flat back at lease end, deferred to today at the deferment rate — typically 5% under Sportelli), and — only below 80 years — half of the marriage value. Relativity (the short lease's value as a percentage of the freehold) drives the marriage-value figure and is the most contested input, which is why the result is a range.
You generally must have owned the flat for two years. The route is: get a RICS valuation, serve a Section 42 notice on the freeholder, negotiate (or, if you can't agree, apply to the First-tier Tribunal), then complete. It typically takes around 6–12 months and costs £3,000–£5,000 in your and the freeholder's reasonable professional fees, on top of the premium itself.
Use the figure in your lease or your service-charge statements — it is property-specific and not available as open data, so never guess wildly. As a benchmark, the English Housing Survey puts leasehold ground rent at around £304 mean and £120 median per year. Enter £0 if you pay a peppercorn (nominal) rent, which makes the term-loss component nil.
The Leasehold and Freehold Reform Act 2024 is set to abolish marriage value, standardise the rates and allow a 990-year extension, which would cut costs for many leaseholders — but the relevant provisions are not yet in force and are unlikely to commence before 2027. Until then the LRHUDA 1993 method above still applies. We will update this calculator when the new rules take effect.

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Service Charge Dispute CheckHouse Valuation CheckTrue Cost of Owning a House

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