Lease Extension Calculator

Years remaining
Ground rent
Value of the flat on long lease
Your Lease Extension Cost

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Things to Note When Using Lease Extension Calculator

Please bear in mind that this lease extension calculator is just for indication purposes and should not be relied on for serving Section 42 or Section 45 notices under Leasehold Reform, Housing and Urban Development Act 1993 or taken as advice.

To obtain accurate costs you should always seek advice from an experienced surveyor who can produce reliable property valuation. 

When you insert the requested variables this leasehold extension calculator will return the premium range in form of low, average and high values.

This calculator does not take into account any rising ground rents and therefore if you have doubling or rising ground rents you should take an average of all increases and add it in the calculator to get the most accurate premium calculation.

When you put in the years remaining on your lease, the calculator will automatically calculate any marriage value interest if it is applicable based on the location you selected and the long lease value of the property.

The location of the property is important and if your property is located in any of the following areas you will need to select the prime central London tab.

Belgravia, Chelsea, Fitzrovia, Holland Park, Kensington, Knightsbridge, Marylebone, Mayfair, Maida Vale, Notting Hill, Pimlico, Regents Park, St John’s Wood.

Frequently Asked Questions

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How Accurate Is Lease Extension Calculator?

A lease extension premium is provided in the form of a range. The valuation is not an exact science and is subject to constantly changing case law and chartered surveyor’s interpretation of evidence. The premium can differ greatly between chartered surveyors due to the subjective nature of the Leasehold Reform Act valuations.

Although we do our best to update the lease extension calculator to reflect changes in the market and case law which has a heavy bearing on lease extension valuation. We cannot fully guarantee the accuracy of this online calculator.

The actual premium agreed might be outside the range quoted by this lease extension calculator.

For accurate assessment of the premium, we always recommend seeking advice from a specialist lease extension surveyor.

We do not recommend using this calculator to serve Section 42 or Section 45 notices. This lease extension calculator should be used as an indication for budgeting purposes only.


How Long Does It Take To Extend The lease?

It depends on whether you are going for an informal or statutory lease extension route.

The informal route is when premium negotiated outside Leasehold Reform Act between leaseholder and landlord and can be agreed to within a matter of days but can also take months. There is no way to guarantee the exact time it will take as it is informal and statutory deadlines do not apply. If informal extension expected to drag on for months it is better to proceed via statutory route forcing the landlord to adhere to set deadlines.

Informal lease extensions are not subject to statutory processes and the landlord can offer an unfair premium or unfavourable lease terms.

Also, when you proceed via informal route landlord will request you to pay his valuation fees. If for some reason you cannot reach the informal agreement. You will need to prepare for a statutory lease extension process where you will once again incur the landlord’s valuation and legal fees.

A statutory process on average takes 8 months from start to finish but can be prolonged if agreement cannot be reached due to parties disputing premium.

If you require more information you can read more about the technical side of the lease extension process in our blog post.

Is Using Surveyor To Extend Your Lease Worth It?

If you are looking to obtain an accurate lease extension valuation, Erikas Grig Chartered Surveyors can prepare a specialist lease extension valuation report which will entail information explaining pitfalls, potential settlement outcomes and lease extension premium for the purpose of serving a statutory Section 42 notice or Section 45 counter-notice.

We have longstanding experience in leasehold valuation matters and can help you save tens of thousands of pounds via negotiation with the landlord or tenant advisors.


If you own a property that has a lease the shorter it becomes the more expensive it will be to extend the lease.

Also, property with short lease tends to fetch less on the market and people are more cautious when leases are below 90 years.

If the lease is approaching 80 years or has dipped below it gets exponentially more expensive to extend the lease and mortgage lenders will be reluctant to lend.


If lease you are going for statutory lease extension then under Leasehold Reform, Housing and Urban Development Act 1993 you are automatically entitled to 90 year extension on top of the existing term.

If lease extension is approached informally then there are no set rules and lease extension term can be anything.



When extending lease via statutory terms upon extension any ground rent becomes obsolete.

The landlord is always compensated for a loss of ground rent and compensation forms part of the total lease extension premium.

If you have onerous ground rent then it may be worth it to extend early instead of waiting for it to increase at the next review date.

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