Job Profit & Margin Calculator

Understanding Job Costs and Profits

Many self-employed tradespeople fall into the trap of looking at their bank account or gross invoice value and assuming they are highly profitable. However, true profit represents what is left over after paying all expenses associated with that job. If you do not track materials cost and your own billable labour hours, you could be working for less than minimum wage.

To calculate the true profitability of a job, you must subtract both materials costs and labour costs from your final invoice quote. The formulas we use to determine this are:

A Worked Example

Suppose you quote a client **£3,000.00** to rewire a small kitchen extension. Your materials (conduit, cable, sockets, consumer unit components) cost **£800.00**. You allocate **24 hours** of work to the job, and you build in a target labor rate of **£25.00 per hour**:

• Built-in Labour Cost: 24 hours × £25.00/hr = **£600.00**
• Total Job Expenses: £800.00 materials + £600.00 labour = **£1,400.00**
• Leftover Job Profit: £3,000.00 quote − £1,400.00 expenses = **£1,600.00**
• Profit Margin: (£1,600.00 ÷ £3,000.00) × 100 = **53.3%**
• Effective Hourly Rate: (£1,600.00 profit + £600.00 labour) ÷ 24 hours = **£91.67 per hour**

This job is highly profitable. You are taking home £600.00 in built-in labour plus £1,600.00 in business profit, yielding a true return of £91.67 for every hour on site.

Three Common Job Costing Mistakes

• Ignoring Small Materials and Consumables: Leaving screws, tapes, sealant, or conduit fittings off your materials budget drains your profits. These small costs are known as "profit leakage."
• Not Tracking Slipped Hours: If you quote for 16 hours but the job takes 24 hours due to unexpected site problems, your effective hourly rate drops. You must log actual hours on site.
• Confusing Revenue with Margin: A £5,000 job with £4,000 in material costs is far less profitable (20% margin, £1,000 profit) than a £2,000 job with £400 in materials (80% margin, £1,600 profit).