Use our lease extension calculator to generate a rough estimate of your potential premium.
While calculators can provide a useful starting point, they rely on simplified assumptions and cannot account for the full range of factors considered in real-world negotiations and tribunal decisions.
LeaseIntel helps leaseholders go beyond generic formulas by benchmarking quotes against comparable tribunal outcomes.
Estimate your premium
Estimated lease extension premium
£27,000 – £36,600
This estimate is generated using simplified assumptions and should not be relied upon as a valuation. Actual premiums can vary materially depending on valuation assumptions, negotiation outcomes and tribunal evidence.
What happens after you use the calculator?
A lease extension calculator — sometimes called a lease extension premium calculator — provides a mathematical estimate using generic valuation assumptions. It is a useful way to estimate lease extension cost quickly, but the output only reflects the inputs and the assumptions embedded in the formula.
LeaseIntel adds the missing layer. Once you have a lease extension estimate from a calculator — or, more importantly, an actual quote from your freeholder — LeaseIntel helps you understand whether that figure appears broadly consistent with comparable tribunal outcomes from similar properties.
Illustrative Example
LeaseIntel Benchmark Preview
Calculator estimate
£31,000 – £36,000
Freeholder quote
£37,900
Comparable tribunal outcomes
from similar properties
£32,400 – £35,500
Assessment
🟠 Above the typical tribunal range
Potential negotiation opportunity
Up to ~£2,400
Confidence
High
Matched against 34 comparable tribunal decisions
Why this matters
Two calculators using different assumptions may produce different estimates for the same flat. LeaseIntel adds another layer by showing how similar cases have actually been resolved at tribunal, helping you understand whether a proposed premium appears broadly within the range supported by comparable decisions.
Illustrative example only. Not based on a real property or tribunal decision.
Why calculators and real outcomes differ
Every lease extension premium calculator applies the same statutory framework, but the numbers behind that framework are matters of professional judgement. Small changes to the assumptions can move the final figure by thousands of pounds.
- Relativity assumptions — the relationship between the short-lease and long-lease value is drawn from different graphs of relativity, each producing different numbers.
- Deferment rates — usually around 5%, but small adjustments have a large effect on the reversion value, particularly on shorter leases.
- Capitalisation rates — used to value the ground rent stream; different rates can meaningfully change the premium where ground rent is high.
- Negotiation between valuers — in practice, freeholder and leaseholder surveyors negotiate on assumptions before any figure is agreed.
- Tribunal discretion — where cases reach the First-tier Tribunal, panels apply their own judgement to the same evidence.
This is why two reputable lease extension calculators can legitimately produce different estimates for exactly the same property — and why comparing an actual quote against comparable tribunal decisions provides context that a formula alone cannot. It is particularly relevant for leases approaching the 80-year threshold where marriage value becomes payable, or where you want to sense-check the total lease extension cost before negotiating.
Already have a lease extension quote?
You do not need to rely on estimates alone. If your freeholder has already proposed a premium, LeaseIntel can benchmark that actual quote against comparable tribunal outcomes — helping you understand whether it appears broadly reasonable before you accept, counter-offer or serve a Section 42 Notice.
Need more than a formula?
A calculator can provide a rough estimate. LeaseIntel compares your quote against comparable tribunal decisions to help you understand whether a proposed premium is within a typical range.
Check My QuoteNot legal or financial advice · Independent benchmarking
How accurate are lease extension calculators?
Calculators are useful as a starting point but they have meaningful limitations.
- They depend on assumptions about deferment rates, relativity and capitalisation that may not match your property.
- They cannot account for all property-specific factors such as condition, location nuances or unusual lease terms.
- Different calculators often produce different answers for the same inputs.
- They do not reflect how negotiations or tribunal decisions actually resolve disputed valuations.
What factors affect lease extension costs?
The premium for a lease extension is driven by several inputs:
- Remaining lease length — the most significant single factor, with a sharp inflection at the 80 year threshold.
- Property value — higher values produce larger premiums in absolute terms.
- Ground rent — capitalised into the premium based on the rent profile.
- Marriage value — an additional element triggered below 80 years. Read more.
- Negotiation outcomes — agreed deferment rates and relativity move the figure materially.
- Tribunal evidence — comparable decisions shape what each side can credibly argue.
Calculator estimate vs tribunal benchmarking
| Calculator | LeaseIntel | |
|---|---|---|
| Method | Formula-based | Tribunal-data-informed |
| Inputs | Generic assumptions | Comparable outcomes |
| Output | Estimate only | Context around whether a quote appears reasonable |
When should you get a more detailed assessment?
A calculator estimate is rarely enough on its own when material money is at stake. Consider a more detailed review in any of the following situations:
- Your lease is below 80 years and marriage value applies.
- There is significant disagreement between you and the freeholder on the premium.
- The figure quoted feels unusually high relative to comparable cases.
- You are preparing for or responding to a Section 42 Notice.
See our lease extension cost guide for a deeper breakdown of the drivers. If you already have a quote, you can check whether your lease extension quote is too high by benchmarking it against comparable tribunal outcomes.
Don't Negotiate Blind
A calculator tells you what the maths might say. LeaseIntel helps you understand what comparable tribunal cases suggest.
Get LeaseIntel ReportNot legal or financial advice · Independent benchmarking
Frequently asked questions
Move from estimate to evidence
A calculator gives you a number. LeaseIntel shows you how that number compares to outcomes in similar real-world cases — so you can negotiate from a position of evidence rather than assumption.
Is My Lease Extension Quote Too High?Independent · Not a valuation or legal advice · Tribunal outcomes, not formula estimates