Move or extend in London? 2026 cost comparison calculator

Your numbers

Adjust the inputs to see your scenario. The page updates instantly as you adjust the inputs.

Your result

Moving is £29,668 cheaper than extending

An extension of this type and size could add roughly £83,200 (≈13%) to your home's value — Nationwide Building Society, October 2025.

Your tipping line

Where moving starts costing more than the extension you selected. The chart follows your inputs above.

Up to about £1,285,000 of target price, moving is the cheaper route in London; beyond that line, extending wins.

Find your borough

All 33 London boroughs covered. Each borough page has local median prices, local council planning portal links, conservation-area notes and a live calculator.

• Barking and Dagenham

  Median £360,000

  Trade-up SDLT from ~£18,750

• Barnet

  Median £590,000

  Trade-up SDLT from ~£38,250

• Bexley

  Median £410,000

  Trade-up SDLT from ~£22,750

• Brent

  Median £575,000

  Trade-up SDLT from ~£36,000

• Bromley

  Median £480,000

  Trade-up SDLT from ~£28,500

• Camden

  Median £920,000

  Trade-up SDLT from ~£90,750

• City of London

  Median £850,000

  Trade-up SDLT from ~£79,750

• Croydon

  Median £420,000

  Trade-up SDLT from ~£23,500

• Ealing

  Median £575,000

  Trade-up SDLT from ~£36,000

• Enfield

  Median £465,000

  Trade-up SDLT from ~£27,250

• Greenwich

  Median £470,000

  Trade-up SDLT from ~£27,500

• Hackney

  Median £650,000

  Trade-up SDLT from ~£47,750

• Hammersmith and Fulham

  Median £880,000

  Trade-up SDLT from ~£84,750

• Haringey

  Median £620,000

  Trade-up SDLT from ~£42,750

• Harrow

  Median £520,000

  Trade-up SDLT from ~£31,500

• Havering

  Median £415,000

  Trade-up SDLT from ~£23,250

• Hillingdon

  Median £455,000

  Trade-up SDLT from ~£26,500

• Hounslow

  Median £530,000

  Trade-up SDLT from ~£32,500

• Islington

  Median £720,000

  Trade-up SDLT from ~£58,750

• Kensington and Chelsea

  Median £1,450,000

  Trade-up SDLT from ~£192,250

• Kingston upon Thames

  Median £595,000

  Trade-up SDLT from ~£38,750

• Lambeth

  Median £615,000

  Trade-up SDLT from ~£42,250

• Lewisham

  Median £475,000

  Trade-up SDLT from ~£28,000

• Merton

  Median £565,000

  Trade-up SDLT from ~£35,250

• Newham

  Median £385,000

  Trade-up SDLT from ~£20,750

• Redbridge

  Median £460,000

  Trade-up SDLT from ~£26,750

• Richmond upon Thames

  Median £760,000

  Trade-up SDLT from ~£65,250

• Southwark

  Median £590,000

  Trade-up SDLT from ~£38,250

• Sutton

  Median £445,000

  Trade-up SDLT from ~£25,500

• Tower Hamlets

  Median £555,000

  Trade-up SDLT from ~£34,500

• Waltham Forest

  Median £520,000

  Trade-up SDLT from ~£31,500

• Wandsworth

  Median £685,000

  Trade-up SDLT from ~£53,250

• Westminster

  Median £1,180,000

  Trade-up SDLT from ~£140,500

No boroughs match.

How the comparison works

Frequently asked questions

Is it cheaper to extend or move in London in 2026?

At London's median family-home value of around £640,000, moving up by 60% to £1,025,000 costs roughly £77,225 all-in — driven mainly by £46,250 of HMRC Stamp Duty. A typical 22 m² mid-spec rear extension runs about £106,893 in 2026. For most homes above £900,000, extending undercuts a like-for-like trade-up.

How much is stamp duty when moving to a more expensive London home?

Stamp Duty Land Tax scales steeply above £925,000 (10%) and £1.5 million (12%) for a main residence. Moving from a £900,000 home to a £1,440,000 one triggers about £67,000 of SDLT — significantly more if you'll still own another property or are a non-UK resident. Verify any figure against HMRC's calculator at tax.service.gov.uk.

How much does a house extension cost in London?

Build rates vary by location: a single-storey rear extension runs around £3,300/m² in outer London, £3,800/m² in inner London and £4,400/m² in prime central boroughs at high specification; side returns and basements cost more per m², lofts and garage conversions less. Add 15% professional fees, 20% VAT and 10% contingency on top of the build cost. Each borough page prices the extension types suited to its housing stock.

Does an extension add value to a London home?

Nationwide Building Society reported in October 2025 that adding a double bedroom can lift a home's value by about 13%, and a full loft plus extension by up to 24%. On a £640,000 London family home that is roughly £83,200 to £153,600 of capital uplift — actual figures depend on the local market and specification.

Do I need planning permission to extend in London?

Some extensions qualify for permitted development (PD) under the GPDO 2015, but London boroughs frequently impose Article 4 directions that withdraw PD rights in specific zones — especially conservation areas. Always check the planning portal of your borough council and the Article 4 status for your address before relying on PD for any extension.

How do I find the rules for my specific borough?

Use the borough index below — every London borough has a dedicated page with local median prices, council planning portal links, conservation-area lists and Article 4 status. The calculator updates live as you adjust the inputs, so you can model your own scenario with borough-specific defaults rather than the London-wide figures shown here.