Extension Calculators

Get a ballpark cost for your kitchen extension based on size, location, and specification.

Estimate how long your kitchen extension will take from planning to completion.

Estimate the total cost of extension foundations including concrete, groundworker labour, digger hire, and access premiums. Adjusts for ground conditions and site access.

Estimate architect, structural engineer, building control, and other professional fees for your extension.

Estimate your kitchen unit and worktop supply cost by supplier tier and worktop material. Calibrated against real UK project data.

Model your monthly payment at the lender's stressed interest rate (FCA MCOB 11.6.18R). Compare your headline payment to the reversion-rate and stressed-rate payments so you know what the lender is testing for before you apply.

Compare further advance, remortgage uplift, second charge, and personal loan side by side for the same target amount. Shows total interest over each route's term so you can see why the cheapest headline rate isn't always the cheapest borrowing.

Get a ballpark cost for your kitchen extension based on size, location, and specification.

Estimate architect, structural engineer, building control, and other professional fees for your extension.

Estimate how long your kitchen extension will take from planning to completion.

Answer a few questions about your property and proposed extension to find out whether you need planning permission, can use permitted development, or may qualify for prior approval.

Enter your extension dimensions to check each PD condition individually. See which limits you pass, which you fail, and what your options are.

Check whether your extension triggers the Party Wall Act 1996. Answer questions about your walls, boundaries, and foundation depth to find out which sections apply.

Generate a suggested six-stage milestone payment schedule for your extension project, aligned with UK industry guidance.

Is your builder’s quote realistic? Enter what it covers and see a traffic-light assessment against typical costs for your region and spec level.

Estimate the cost of moving gas, electric, and water meters before your extension build. Includes trenching and consumer unit moves.

Estimate the total waste volume from your extension project and how many skips you will need, based on floor area, demolition scope, and strip-out works.

Estimate how much ready-mix concrete you need for your extension foundations, how many mixer loads to order, and what it will cost delivered.

Estimate the total cost of extension foundations including concrete, groundworker labour, digger hire, and access premiums. Adjusts for ground conditions and site access.

Estimate how much spoil your extension dig produces (volume and weight) and how many grab lorry loads it takes to remove, from the topsoil strip and foundation trench dimensions.

Estimate the hardcore, sand blinding, DPM, PIR insulation, and concrete you need for a ground-bearing extension floor, by floor area and layer depths, with an all-in cost.

Estimate how many blocks, bricks, cement bags, and sand you need for your extension walls -- with a materials cost range.

Estimate the insulation thickness, board count, and material cost to aim for the Part L building regulations targets for your extension walls, roof, and floor. A budgeting estimate, not a U-value calculation.

Estimate steelwork costs for your extension based on the number and type of structural openings, whether a cantilever or ridge beam is needed, and your house age.

Estimate rafter count, ridge board length, wallplate lengths, and approximate timber supply cost based on your extension dimensions, roof type, and pitch.

Estimate tile counts, batten lengths, underlay rolls, and supply costs for your extension roof based on dimensions, pitch, roof type, and tile choice.

Estimate your extension windows and doors budget: windows by size, material, and opening style; bifold or sliding doors with optional integrated blinds; plus sealing costs. Reads graph-backed 2026 market pricing with bespoke-tier overrides for aluminium.

Compare the installed cost of bifold and sliding doors for your extension opening. Pick size, material, and tier; see both totals side-by-side with a width-based recommendation.

Estimate your kitchen unit and worktop supply cost by supplier tier and worktop material. Calibrated against real UK project data.

Estimate your total appliance supply budget by selecting what you need and your brand tier — from budget to premium.

Estimate how long your kitchen will take to fit and what it will cost — based on unit count, worktop type, island, and appliance connections.

Check whether your room dimensions work for your chosen layout — galley gap, island clearance, and work triangle checks against recommended minimums.

Estimate the cost of liquid or traditional floor screed — and optional underfloor heating system — for your extension floor area.

Calculate how long before you can walk on your screed, commission underfloor heating, and tile over it.

Estimate your total plumbing spend for a UK kitchen extension: first fix, second fix, boiler work, underfloor heating, and add-ons. Calibrated against a documented build's plumbing quote and what was finally paid.

Estimate the full electrical budget for your kitchen extension: first and second fix labour, fittings, consumer unit work, outdoor lighting, smart home additions, and certification.

Calculate how many tiles you need for floor and walls, plus adhesive, grout, and a fitting budget range — calibrated against real UK project data.

Estimate flooring supply and installation costs for your extension based on floor area and material choice — LVT, engineered wood, solid hardwood, carpet, polished concrete, or porcelain.

Calculate how many plasterboard sheets you need for your extension walls and ceiling, plus screws, jointing compound, and supply cost estimate.

Calculate how much paint you need for walls, ceilings, and woodwork in your extension — with a supply cost estimate for budget and mid-range brands.

Estimate the total cost of external works after your extension is complete — lawn, patio, driveway, fencing, and drainage reinstatement.

Track which completion certificates you have obtained and which are still outstanding before your building control final inspection.