Get an initial illustration
Use your long-lease flat value, remaining years and annual ground rent. Check the assumptions against your lease.
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Lease extension
calculator
A lease extension calculator estimates the premium a flat leaseholder in England and Wales may pay to extend a lease. The figure depends mainly on unexpired term, ground rent and property value. Lease Extension Pro provides a simplified educational estimate with visible assumptions—not a RICS valuation or legal advice. Instruct a solicitor and valuer before any Section 42 notice.
✓Free to use✓No sign-up needed✓England & Wales
Your home. A longer future.Start with a little more clarity.
Your starting point
A little more certainty.
A better next step.
Enter your flat’s details to see an illustrative premium and a transparent breakdown.
Your inputs have changed. Recalculate to update this result.
- Ground rent component
- —
- Reversion component
- —
- Marriage value
- Not assessed yet
Premium only. Legal fees, valuation fees and other costs are not included.
A guide, not a valuation. This is a simplified illustration, not a Section 42 notice figure. For leases of 80 years or fewer, we show components only and withhold a full premium. Read the limitations.
Independent guidance. Official sources for context.Not affiliated with either organisation
From estimate to informed decision
Understand your next steps.
The calculator is a starting point—not the whole journey. Here’s how to put your result in context.
Look at the whole budget
The premium is one part of the cost. Allow for valuation, legal work and any applicable landlord’s costs.
Explore lease extension costsSpeak to the right professionals
A specialist valuer and solicitor can assess your actual lease, legal route and proposed notice figure.
Choosing a solicitorNo black box. Just clear assumptions.
How the calculator
works.
Lease Extension Pro models two elements for an England & Wales flat: the present value of ground rent lost, and the value of delaying the landlord’s reversion. These are educational assumptions, not a professional valuation model.
- Flat value means its assumed long-lease value in £.
- Default rates: 7% capitalisation and 5% deferment; both are editable assumptions, not verified market rates.
- The model uses an additional 90 years and constant rent. Rent reviews, intermediate interests, development value and reforms are excluded.
- A full estimate is withheld at 80 years or fewer: marriage value and lease relativity require specialist assessment.
Formula: rent × [1 − (1 + c)−t] ÷ c + value × [(1 + d)−t − (1 + d)−(t + 90)], where t is years, c capitalisation and d deferment as decimals.
Read the statutory valuation context: Schedule 13 ↗The statutory source is context; it does not validate our simplified formula. Check current commencement and amendments with your advisers.
A worked example
Let’s put some numbers to it.
Long-lease flat value£300,000Remaining term85 yearsGround rent£200 / year
- Ground rent component at 7%
- About £2,850
- Reversion component at 5%
- About £4,680
- Marriage value
- Excluded in this model
Illustrative premiumAbout £7,530
Rounded to the nearest £10. Not an actual transaction, market quote or all-in budget. The calculator displays rounded components; totals are calculated before rounding.
A little knowledge goes a long way
Make sense of your lease.
Lease extension, explained
Understand the basics, the statutory route and how an informal agreement differs.
Read the guide ↗What does it really cost?
Look beyond the premium. Get a clearer picture of the costs to ask about.
Understand the costs ↗From first step to completion
Follow the process, from checking your lease to valuation and legal completion.
See how it works ↗Good questions. Clear answers.
A few things
worth knowing.
Some common questions before you take your next step.
Read our full disclaimer ↗How much does a lease extension cost?
The total includes the premium plus valuation and legal work, and may include certain landlord costs. Lease Extension Pro illustrates the premium only, not a complete budget. See the cost breakdown and LEASE guidance.
What happens if my lease is under 80 years?
Short-lease valuation can involve marriage value under the traditional statutory framework. Our simplified model cannot assess this reliably, so it withholds a full premium at 80 years or fewer. Ask a specialist to check the applicable valuation rules and current reforms.
Is this the official LEASE calculator?
No. Lease Extension Pro is an independent educational project, not the Leasehold Advisory Service (LEASE), a government service or a law firm. For independent official guidance, visit LEASE.
Can I use this figure on a Section 42 notice?
No. Do not use this illustration as your proposed notice premium. Instruct a specialist valuer and solicitor to determine the appropriate figure and check your eligibility before serving a notice.
Does this apply in Scotland?
No. This tool concerns flats in England and Wales only; Scotland has a different property-law framework.