How I price

The sources, by name

The UK ranges are validated against public national cost guides. On 26 August 2026 every guide behind every project was opened and re-checked, and each cost guide page on this site now lists its own sources with their published figures, dates and VAT treatment, so you can compare my range against theirs on the page itself. The four source families:

• Checkatrade cost guides
• MyJobQuote pricing guides
• MyBuilder pricing guides
• HomeOwners Alliance guides

Where a guide states its prices exclude VAT, I add 20% VAT and say so next to that source. Where a guide does not state its VAT treatment, that is shown too, instead of a silent assumption. Most guides do not say, so I cannot promise that a range includes VAT: ask each trade whether VAT comes on top. A trade under the £90,000 VAT threshold is often not registered and then charges none. The US planning ranges are validated separately against US cost guides, with metro factors on top; the UK planning permission rules follow Planning Portal (planningportal.co.uk) and the HomeOwners Alliance permitted development guide, checked 3 August 2026.

The method

• Each project type gets a national mid-range band from the guides above (data set last verified 26 August 2026).
• Your finish level changes that band. The guides price each finish level only for bathroom renovation, so there I use their bands. For every other project no guide splits cleanly by finish, so the levels are my own assumption, kept inside the spread the guides publish.
• Your region scales it again: 9 regional factors, from London (+25%) down to Northern Ireland (-20%), also taken from the guides.
• One data file drives the calculator, every cost guide page, the quote check and the budget planner, so no two pages on this site can disagree about the same project.

Finish levels, project by project

• Kitchen renovation (my assumption): Checkatrade splits kitchens into budget, mid-range and bespoke, but the three overlap so much that they cannot carry a level on their own. I keep my levels inside the overall spread of both guides.
• Bathroom renovation (from the guides): MyJobQuote prices budget, standard and premium bathrooms separately, and Checkatrade's basic refresh, low to medium and high end land in the same places. I use those bands as they are.
• Wet room (my assumption): The guides split wet rooms by size, not by finish.
• Loft conversion (my assumption): Checkatrade gives a low, average and high price per loft type, not per finish. Budget runs from low to average, mid-range is the full band, and premium runs from average to high plus up to £3,000 for premium finishes, the figure MyJobQuote names.
• Rear extension (my assumption): Both guides split extensions into levels. My budget and premium stay inside what they publish for those levels, but my mid-range follows Checkatrade's wider rule of thumb of £1,800 to £3,000 per m² plus VAT.
• Side return extension (my assumption): One guide covers this project, and it gives a single band per m² with no split by finish.
• Garage conversion (my assumption): The guides split garage conversions by type and size, not by finish.
• Full house renovation (my assumption): MyBuilder runs from basic cosmetic updates to a high-end remodel: one sliding scale, not three levels.
• Rewiring (3-bed reference) (my assumption): The guides price rewiring by house size. One MyJobQuote quote calls itself a basic rewire, too thin to build a level on.
• New boiler / central heating (my assumption): MyJobQuote names a mid-range combi band, but no guide gives a full split by finish.
• Windows & doors (my assumption): The guides split windows by material and style, not by finish level.
• Damp proofing (my assumption): The guides split damp work by treatment, from injection to tanking, not by finish.
• Driveway & patio (my assumption): The guides split surfaces by material, not by finish level.
• Painting & decorating (my assumption): The guides give a band per m² and prices per room, not a split by finish.

What this is not

An estimate here is a planning range, not a quote. It cannot see your property, your access, your ground or your taste. Use it to set a realistic budget, to sanity-check quotes and to compare options; then let itemised quotes from local trades decide. What you enter stays in your browser unless you send it yourself, and no one pays to influence the numbers.

Start with the cost calculator, or put a quote you already have through the quote check.