Resources

Lease extension calculator

This free calculator estimates a statutory lease extension premium for flats in England and Wales using the Deritend blended relativity methodology established in tribunal case law — paired with Schedule 13 of the 1993 Act (and a standard 5% deferment rate following Sportelli).

No account is required: enter your years left, an estimated long-lease value, and ground rent, then get an instant ballpark figure to support planning conversations with a surveyor or neighbours.

If your building has already exercised Right to Manage, you are in a strong position to coordinate extensions as a group — sharing professional fees and aligning timing, while day-to-day building spend stays under transparent self-management rather than a distant landlord or agent. For tenure basics, see leasehold vs freehold explained; browse the full resources hub for tools alongside this one.

Legislative changes proposed under the Leasehold and Freehold Reform Act 2024 may alter premiums in future — read our summary for timings.

Years remaining on your lease

Check your lease document or the Land Registry title register.

Estimated property value

The current open market value of your flat as if it had a long lease.

Annual ground rent

Enter 0 if your lease has a peppercorn (zero) ground rent.

New to leases and tenure? Read leasehold vs freehold explained · Leasehold and Freehold Reform Act 2024 · resources hub.

Frequently asked questions

Short answers for orientation — not tailored to your lease or building.

How accurate is this estimate?

This calculator uses the Deritend blended relativity methodology endorsed by the Upper Tribunal, combining two relativity curves whose methodology was established in tribunal proceedings. It gives a reliable ballpark figure but the actual premium depends on professional valuations from both parties and may be negotiated or determined by the First-tier Tribunal. Use it as a starting point, not a final figure.

What is marriage value and why does it matter?

Marriage value is an additional component that applies when a lease has fewer than 80 years remaining. It represents the increase in your property's value that results from extending the lease. Under the 1993 Act, leaseholders must share 50% of this uplift with the freeholder. This is why premiums rise sharply below 80 years — and why extending before you reach 80 years can save thousands of pounds.

Should I extend my lease or do Right to Manage first?

They are not mutually exclusive. RTM gives you control over building management and does not directly affect your lease length. However once your RTM company is in place, leaseholders can coordinate lease extensions collectively — sharing professional costs and negotiating from a stronger position. Many leaseholder groups do RTM first, then address lease extensions together. Read what is the Right to Manage?.

What is the deferment rate?

The deferment rate of 5% is the standard used by the vast majority of valuers and tribunals in England and Wales following the Sportelli case [2007] 1 EGLR 153. It represents the annual return the freeholder is assumed to require from holding the freehold interest.

Will the Leasehold and Freehold Reform Act 2024 change the cost?

Yes — but the new rules are not yet in force. The 2024 Act is expected to change the valuation methodology in ways that reduce premiums for most leaseholders. However the detailed valuation rules depend on secondary legislation that has not yet been made. This calculator uses the current rules which remain in force. See our guide on the Leasehold and Freehold Reform Act 2024 for what has and has not yet changed.

Explore Right to Manage while you plan lease decisions — eligibility takes about two minutes.

Check eligibility