How to Calculate Labour Cost for a Trade Job

Labour cost is the number most tradespeople get wrong when quoting. Not by accident — by omission. The basic sum (workers × hours × rate) is straightforward. What goes missing is everything built around it: National Insurance, travel, tool wear, and the time you spend on admin you cannot bill.

This guide walks through every component of labour cost calculation with worked examples. For quick calculations, use the labour cost estimator which handles the maths automatically.

The Labour Cost Formula

Total labour cost = (workers × hours/day × days × hourly rate) + employer NI + travel + overhead

Each component has a real value. Leaving any of them out means quoting a number that looks right but loses money.

Step 1: Basic Labour

The foundation is straightforward:

Basic labour = number of workers × hours per day × number of days × hourly rate

A 2-person team working 8 hours/day for 5 days at £42/hour: 2 × 8 × 5 × £42 = £3,360

This is the floor, not the ceiling. Everything below gets added on top.

Step 2: Employer National Insurance

If you employ workers on PAYE, employer NI must be included. In 2026 the rate is 13.8% on earnings above £175/week (the secondary threshold).

For a worker earning £42/hour × 40 hours/week = £1,680/week:

• Earnings above threshold: £1,680 − £175 = £1,505
• NI cost: £1,505 × 13.8% = £207.69/week per employee

On a 5-day (1-week) job with 2 employees: 2 × £207.69 = £415

This is real money that disappears from your margin if you forget it. On a 2-week job with 3 employees, employer NI alone can add £1,200–£1,500 to your cost base.

Note: Self-employed subcontractors do not attract employer NI. If you are using CIS subbies, this step does not apply — but CIS deduction rules still govern what you pay them.

Step 3: Travel

Travel costs are chronically underestimated on longer jobs. A crew of 3 driving 20 miles each way in one van:

• 40 miles/day × 45p/mile (HMRC approved rate) = £18/day just in fuel allowance
• Plus 1–1.5 hours of driving time at your team's hourly rate

On a 2-week job that is £180+ in mileage alone, before the time cost. Use a daily travel allowance in your quote — the labour cost estimator has a field for this.

Step 4: Overhead Markup

The 15–25% markup applied to labour is not profit — it is overhead recovery. It covers:

• PPE replacement (helmets, gloves, boots, harnesses)
• Tool wear and replacement (power tools, hand tools, consumables)
• Public liability and employer's liability insurance allocated to the job
• Training and CSCS renewals
• Sick pay and holiday pay (for PAYE employees)
• Pension contributions (minimum 3% employer contribution under auto-enrolment)
• Your time managing the team, handling issues, and communicating with the customer

A 20% markup on labour is not excessive. It is often the minimum required to break even on real employment costs. Many tradespeople underprice this because these costs feel invisible until they are not.

Worked Example: Kitchen Refurb in Bristol

A sole trader with 2 employed plasterers and tilers:

• 3 workers, 8 hours/day, 4 days
• Hourly rate: £40
• Travel: £30/day total
• Include employer NI: yes

Quoting just "3 workers for 4 days at £40/hour" gives £3,840 — a £1,309 shortfall before the customer even questions a single line.

Labour vs Materials: Separating the Quote

Labour and materials should always be separate line items. This makes it clear what the customer is paying for the work versus what they are paying for the materials, and protects you if material prices change between quote and job.

For materials pricing, a 20–35% markup is standard. The material markup calculator shows your true margin after VAT and handles the markup vs margin distinction that trips up most tradespeople.

Labour Cost Per Square Metre

For area-based work (plastering, tiling, flooring, painting), customers often ask for a price per m². To calculate:

Labour cost per m² = total labour cost ÷ total area (m²)

Using the example above: £5,149 ÷ say 120 m² = £42.91/m² labour charge

Add materials separately, and you have a clean, defensible per-m² quote.

The Fastest Way to Get This Right

Manual calculation is accurate but slow. For every job over 2 days, the time spent working through workers × hours × days × rate × NI × travel × markup exceeds what an automated tool saves you.

The labour cost estimator calculates all four components in real time as you adjust sliders. Once you have the labour figure, combine it with the material markup calculator to build the full job quote — or use the AI quoting tool to generate a complete itemised quote from a job description in minutes.

Frequently Asked Questions

What is the difference between labour cost and labour charge? Labour cost is what it costs you — basic wages, NI, travel, overhead. Labour charge is what you invoice the customer — cost plus markup. The gap between the two is your margin.

Should I include admin time in my labour cost? Yes, but typically as part of the overhead markup rather than as a billable line item. If a job requires significant management time (coordinating subbies, dealing with planning issues, multiple site visits), add a management fee line to the quote explicitly.

How do I calculate labour cost if I am a sole trader? For sole traders, the NI calculation is different — you pay Class 4 NI on profits rather than employer NI per worker. The basic labour cost formula still applies: your day rate multiplied by the number of days. Add a 20% overhead allowance for tools, insurance, vehicle, and admin, and that is your labour charge before materials.