Use this leasehold calculator to estimate a potential lease extension premium, including term value, reversion value, and marriage value. It is designed as an educational planning tool for UK-style leasehold properties.
Lease Extension Premium Estimator
Enter your figures below. All currency values are in GBP (£).
What this leasehold calculator helps you estimate
This tool gives you a practical estimate of lease extension cost. It combines three major components commonly discussed in leasehold valuation: loss of ground rent (term value), loss of future reversion, and marriage value when the lease has dropped below 80 years. You can also include legal and valuation costs to see a broader “all-in” number for planning.
How the calculation works
1) Term value (ground rent loss)
The freeholder gives up some or all of the future ground rent stream. The calculator discounts those future payments back to today using your selected capitalisation rate.
2) Reversion value
Without an extension, the freeholder would receive the property back sooner. With an extension, that reversion is delayed. The calculator estimates the present value of this delay using a deferment rate.
3) Marriage value (if under 80 years)
When a lease is below 80 years, extending it often creates additional value. Under statutory assumptions, part of that uplift can be shared with the freeholder. This estimator applies a simplified 50% share of eligible uplift where appropriate.
Inputs explained
- Property value: the current market value of the flat/house with a long lease assumption.
- Current annual ground rent: your existing yearly ground rent amount.
- Years remaining: critical for value and especially important around the 80-year mark.
- Extension years: useful for exploring statutory vs informal deals.
- Capitalisation & deferment rates: valuation assumptions that strongly influence premium estimates.
- Relativity: if left blank, the calculator uses an automatic estimate based on years remaining.
Why the 80-year threshold matters
Crossing below 80 years is often the biggest jump point in lease extension pricing because marriage value can be triggered. If your lease is close to 80 years, running scenarios at 79, 80, and 81 years can be very useful. This helps you see how timing might affect total cost.
Practical tips before you rely on any estimate
- Use this as a planning range, not a final legal valuation.
- Get a specialist leasehold surveyor for a formal premium opinion.
- Ask your solicitor to review statutory rights and deadlines.
- Compare statutory route vs informal offer terms carefully.
- Model different rate assumptions to understand sensitivity.
Frequently asked questions
Is this calculator legally binding?
No. It is an educational estimate. Official premium outcomes depend on negotiated evidence, valuation reports, and legal process.
Can I use this for any leasehold property?
You can use it for broad guidance on many leasehold scenarios, but complex rent review clauses, unusual lease terms, or local market conditions may materially change results.
What should I do after calculating?
Print or save your results, then share them with a solicitor and valuer. Ask for a professional lease extension strategy based on your lease terms and timeline.
Final thought
A good leasehold calculator helps you ask better questions before spending money on the process. Use it to prepare, compare options, and move forward with professional advice when you are ready.