How Builders Should Calculate Costs for a Job: Pricing Guide UK (2026)

If you ask ten builders how they price a job, you will get ten different answers. Some work off square metre rates. Some use day rates. Some just "know" what a job should cost based on experience. And some guess and hope for the best.

The problem with guessing is that it works until it does not. One underpriced extension or loft conversion and you are working for weeks at a loss. One overpriced kitchen and you lose the job to a builder who actually did the maths.

This guide walks through a proper method for calculating building costs. It is not complicated, but it is thorough. And thorough pricing is what separates builders who make good money from builders who just stay busy.

The Five Cost Categories

Every building job, no matter how big or small, has five categories of cost. Miss any one of them and your price will be wrong.

1. Labour. This is your time and, if applicable, your team's time. It includes the hours on site, plus travel time, time spent buying materials, and time spent on admin for the job.

2. Materials. Everything from bricks and cement to screws and dust sheets. The actual cost of the physical stuff that goes into the build.

3. Plant and equipment. Anything you need to hire or run for the job. Mini diggers, cement mixers, scaffolding, skip hire, generators. If you own the equipment, you should still factor in depreciation and running costs.

4. Overheads. Your ongoing business costs that exist whether you are on a job or not. Van, insurance, accountant, phone, tools, workwear, advertising, and admin time.

5. Profit. The money you actually keep after all costs are covered. This is not your wage. Your wage is part of labour. Profit is the return on running a business and taking the risk.

Step 1: Work Out Your Labour Costs

Start by knowing your own day rate. If you are a sole trader, your day rate needs to cover your personal income, your National Insurance, your pension contributions, and a buffer for quiet periods and holidays.

Let us say you want to take home 40,000 pounds a year. After tax and NI (roughly 25% for a sole trader at this level), you need to earn about 53,000 gross. Divide that by your working days. Most builders realistically work 230 to 240 days a year once you subtract weekends, bank holidays, a couple of weeks off, and the odd weather day. That gives you a personal day rate of about 220 to 230 pounds.

But that is just your wage. If you employ labourers or subcontractors, add their day rates too. A general labourer in the UK typically costs 120 to 160 pounds per day. A skilled subcontractor (bricklayer, plasterer, roofer) will cost 200 to 350 depending on the trade and region.

For our example, let us say you are pricing a single-storey rear extension. You estimate 15 days on site with one labourer for 10 of those days. Your labour cost is: 15 days x 230 (you) + 10 days x 140 (labourer) = 3,450 + 1,400 = 4,850.

Use our day rate calculator to get your exact figure based on your actual overheads and income target.

Step 2: Price Up Materials

This is the part that requires the most homework. You cannot price materials from memory because prices change constantly, and guessing is the fastest route to losing money.

For a single-storey extension, your materials list will typically include: foundations (concrete, rebar, membrane), blockwork and brickwork (blocks, bricks, cement, sand, lintels, DPC), roof structure (timber, felt, tiles or slate, fascias, soffits, guttering), insulation, windows and doors, internal finishes (plasterboard, plaster, floor screed), and first fix carpentry (stud walls, door liners).

Get actual quotes from your merchants for the main items. Use builder's merchant trade accounts for accurate pricing. Do not use retail prices from B&Q or Wickes as your baseline.

For our example extension (roughly 4m x 5m), a realistic materials budget in 2026 might look like: foundations and groundwork materials 1,800, blockwork and brickwork 2,400, roof structure and covering 3,200, windows and bifold door 2,800, insulation 600, plasterboard and plaster 500, sundries and fixings 400. That is a materials total of roughly 11,700.

Add a markup of 10 to 15 percent on materials. This covers your time sourcing, ordering, collecting, checking deliveries, and managing any returns. On 11,700, a 12% markup adds 1,404, giving you 13,104 for materials.

Step 3: Include Plant, Skip, and Scaffolding

These are the costs that builders often forget or underestimate. For our extension example: mini digger hire for foundations (2 days at 150) is 300, scaffolding for the full build (4 to 5 weeks) is 900, skip hire (2 skips) is 500, and a cement mixer hire (3 weeks) is 200. That gives a plant and equipment total of 1,900.

Always get actual hire quotes. Do not guess. And remember to factor in delivery and collection charges, which can add 50 to 100 per item.

Step 4: Add Your Overheads

Your overheads are the costs of running your business. Some builders absorb these into their day rate. Others charge them as a percentage on top. Either way, they need to be accounted for.

Typical annual overheads for a self-employed builder: van finance or depreciation 3,000 to 5,000, fuel 3,000 to 5,000, van insurance 1,200 to 2,000, public liability insurance 400 to 800, tool replacement and maintenance 1,000 to 2,000, accountant 600 to 1,200, phone and admin 500 to 800, workwear and PPE 300 to 500, advertising and website 500 to 1,500.

That totals roughly 10,500 to 18,800 per year. If you work 235 days, that is 45 to 80 pounds per day in overheads. For simplicity, many builders roll this into their day rate. If your personal day rate is 230 and your daily overhead is 60, your effective rate is 290 per day.

If you have already included overheads in your day rate calculation (as we did in step 1), you do not need to add them again here. Just make sure they are covered somewhere.

Step 5: Add Contingency

Building work always throws up surprises. Bad ground conditions, hidden asbestos, rotten timber that was not visible before stripping out. A contingency of 5 to 10 percent on the total job cost is standard for new build work. For renovation work on older properties, go higher at 10 to 15 percent.

Some builders include this in their profit margin rather than showing it separately. Others show it as a provisional sum that is only charged if needed. The advantage of showing it separately is that if you do not use it, the customer sees a lower final invoice and feels they got a good deal.

Step 6: Add Your Profit

Profit is not your wage. Your wage was covered in the labour calculation. Profit is the reward for running a business, managing the job, taking financial risk, and dealing with all the hassle that comes with being self-employed.

A reasonable profit margin for building work is 10 to 20 percent on top of all costs. On our example extension, the costs so far are: labour 4,850, materials (with markup) 13,104, plant and equipment 1,900. That is a subtotal of 19,854. A 15% profit margin adds 2,978, bringing the total to 22,832.

If you are VAT registered, add VAT on top: 22,832 + 20% = 27,398 including VAT.

That is a properly costed price. Not a guess, not a rough figure, not "what the last one cost plus a bit." Every pound is accounted for, and you know exactly what your margin is. Check your margins with our profit margin calculator.

Step 7: Present It Properly

You have done all this work to calculate a fair, profitable price. Do not undermine it by scribbling it on a bit of paper or texting "22k plus VAT for the extension."

Send a professional PDF document. Include your business name and contact details, the customer's details, a detailed scope of work describing exactly what is included, an itemised price breakdown (you do not need to show your raw costs, but separate labour, materials, and plant at minimum), a clear timeline, payment terms, and your validity period.

For a full guide on structuring building quotes, read our guide to quoting for building work or download our free builder's quote template.

If you want to speed this up, QuoteSmith generates professional, branded building proposals in minutes. Enter the job details, and it creates a detailed PDF with scope, pricing, terms, and your branding. See some example proposals to understand the quality.

Common Pricing Mistakes Builders Make

Not pricing your own time for quoting. If you spend 3 hours surveying, measuring, and pricing a job, that is time you could have been on site earning. Factor a percentage of your quoting time into your overheads or markup.

Using last year's material prices. Timber, steel, and insulation prices can shift significantly in a matter of months. Always get fresh merchant quotes for any job over 5,000 in materials.

Forgetting subcontractor costs. If the job needs an electrician, plumber, or plasterer, get their quotes before you price the job. Do not estimate what they will charge. Ask them.

Not accounting for Building Control fees. Building Regulations approval for an extension typically costs 400 to 900 depending on your local authority. Include it in your quote or clearly state it is excluded.

Competing on price. If you are always the cheapest quote, you are underpricing. The customer who picks the cheapest builder is not the customer you want. Price fairly, present professionally, and let the quality of your quote do the selling.

Frequently Asked Questions

How much do builders charge per day in the UK in 2026?

Self-employed builders in the UK typically charge between 200 and 350 pounds per day. In London and the South East, day rates commonly run from 300 to 450 pounds. Experienced builders running their own projects may charge 350 to 500 pounds per day when their overhead and management time is factored in.

What markup should builders add to materials?

Most builders in the UK add a markup of 10 to 20 percent on materials. This covers the time spent sourcing, ordering, collecting, and managing deliveries, as well as the risk of price increases between quoting and purchasing. Some builders pass materials through at cost and charge a separate management fee instead.

How much contingency should a builder add to a quote?

For standard building work, a contingency of 5 to 10 percent is normal. For renovation work on older properties where hidden issues are more likely, 10 to 15 percent is more appropriate. If you show it as a separate line, explain to the customer that it is only used if unforeseen issues arise and any unused contingency is not charged.

Should builders give a fixed price or a day rate?

For clearly defined work like extensions, loft conversions, or new builds with approved plans, customers strongly prefer a fixed price because it gives them budget certainty. For less predictable work like renovations of older properties, a day rate with an estimated duration may be more appropriate. Fixed price quotes generally win more work because customers feel more in control.