How to Calculate Staff Costs Per Project Using Timesheet Data
Most businesses can tell you what they spent on payroll last month. Asking them what a specific project actually cost in labour? You'll get either a spreadsheet or a blank stare.
This gap—between what you spend overall and what specific work actually costs—is where profitability disappears. One project quietly kills your margins. Another looks bad on paper but actually printed money. You won't know which is which until you calculate staff costs per project.
If you run a service business, a trades company, a professional practice, or any operation where team members spend time on specific clients or projects, this is not optional. It determines your pricing. It reveals which work is worth pursuing. It shows you where to allocate resources. And it answers the question every small-business owner asks on Sunday night: "Are we actually making money on this?"
This guide explains how to use timesheet data to calculate accurate staff costs per project, and what to do once you have the numbers.
Why You Need to Know Project Costs
Pricing that reflects reality, not hope
If you don't know what past projects cost, your pricing is educated guessing. You win work because your quote is too low (and you regret it mid-delivery). Or you lose work because your quote is too high (based on assumptions that didn't hold up). Historical cost data—pulled from timesheet records—brings your estimates back to earth.
A web design firm quotes 120 hours at £50/hour for a rebrand. They win the job. Six months in, timesheets show it actually took 200 hours. Next rebrand quote includes that learning. That's how pricing gets smarter.
Knowing which work actually makes money
Revenue minus labour cost equals profit. If you know the revenue from a project but not the labour cost, you cannot calculate whether you made money. A project that billed £20,000 might have cost £18,000 in labour (respectable margin) or £22,000 (you paid to do it).
Timesheet data removes the guesswork.
Smarter resource planning
When you know which projects chew through the most hours, you can staff them differently. Maybe that high-labour task can be automated. Maybe it needs a junior team member instead of a senior one. Maybe you decline similar work altogether because the margin is not worth the distraction.
Timesheet data helps you forecast staffing needs exactly because it shows you what labour actually costs per task.
Talking to clients from a position of fact
When a client asks for a discount, or disputes a fee, or wants to know why the invoice is higher than expected, project cost data gives you a concrete answer. "This scope took 145 labour hours to deliver. At our fully loaded rate, that's £5,075 in labour cost alone. Here's the breakdown." That's not arbitrary. That's factual.
How to Calculate It
The formula is simple. The execution requires a bit of care.
Labour cost per project = Total hours worked × Fully loaded hourly rate for each person
Step 1: Track time by project
This is the foundation. Your timesheet system must let people record which hours went to which project. It might look like:
- A project code selected when clocking in
- A time split entered by end of day ("4 hours on Project A, 4 hours on Project B")
- Automatic allocation based on location (for businesses where each client site is a separate project)
The mechanism varies. The principle is the same: every hour must be tied to a specific project.
If your current system doesn't do this—if people clock in and you have no idea which project that time went to—you cannot calculate project costs. This is why setting up a proper timesheet system is the first step, not the last.
Step 2: Calculate the fully loaded hourly rate
Here's where most small businesses trip up. The cost of an hour of labour is not just the person's wage.
The fully loaded rate includes:
- Gross pay: Hourly rate, or salary divided by annual working hours
- Employer taxes: Employer's National Insurance contributions in the UK; FICA taxes in the US
- Pension contributions: If you match employee contributions, that's a cost
- Benefits: Health insurance, phone allowance, car allowance, gym membership—whatever you offer
- Holiday pay: Paid time off, spread across the hours actually worked
- Sick pay: Expected cost of paid sick leave
- Training: Professional development and upskilling
- Overhead allocation (optional, but realistic): A share of office rent, management, and administration
A common rule of thumb: the fully loaded cost is 1.3x to 1.5x gross pay, depending on your jurisdiction and benefits. A person earning £25/hour gross might actually cost you £33–£38/hour when everything is baked in.
Calculate this for each person or job category. (People in the same role at the same level usually have similar fully loaded costs.)
Step 3: Multiply, then add
For each person on the project, multiply their hours by their fully loaded rate. Then add them up:
| Person | Hours | Loaded rate | Cost |
|---|---|---|---|
| Alice | 40 | £35/hr | £1,400 |
| Bob | 25 | £28/hr | £700 |
| Carol | 10 | £45/hr | £450 |
| Total | 75 | — | £2,550 |
That's your labour cost. Compare it to what you charged (or budgeted), and you know your margin.
Step 4: Add non-labour costs
For a complete picture, include direct costs that are not labour:
- Materials and supplies
- Subcontractor fees
- Travel and site expenses
- Software licences specific to the project
- Equipment hire or rental
Labour is usually the biggest line item, but an honest project cost includes everything that would not exist if the project didn't happen.
What to Do With the Data Once You Have It
Compare estimates to actuals
For every project, line up what you estimated to cost against what it actually cost. If your actuals are consistently higher than your estimates, your pricing is too low or your estimates are too optimistic. If actuals are consistently lower, you may be over-pricing.
One plumbing firm found that emergency call-outs were running 30% over estimate. Next year, they quoted emergency work 30% higher. No customer complaints, slightly better margins.
Spot which types of work are actually profitable
Group projects by type—"new installations vs. maintenance", "large corporate clients vs. small", "recurring support vs. one-off builds"—and compare margins. You may discover that one category is 20% more profitable than another.
That changes what you pursue, what you charge, and how you staff it.
Optimise your labour mix
A project staffed entirely by senior people costs more than the same project done by a mix of senior and junior staff. If your quality standards allow, moving routine work to less experienced (and less expensive) team members improves margins without compromising output.
Timesheet data also helps you spot burnout when people are consistently overloaded, which is both a human issue and a cost issue.
Track efficiency gains
As your team gets better at a particular type of work, labour costs per project should fall. Timesheet data lets you verify this. Is the average cost per similar project trending down? If not, that's a signal to investigate.
Feed billing and invoicing
If you bill clients on a time-and-materials basis, timesheet data flows directly into the invoice—cleanly, and with an audit trail. If you bill on a fixed-fee basis, the data tells you whether the fixed price is viable or unsustainable.
Common Pitfalls
People who don't log time by project. If team members are haphazard about it, the data is worthless. Make it mandatory. Use a system that makes it easy—a dropdown at clock-in, a tag in the timesheet, or automatic allocation. And enforce it consistently.
Shared or overhead time. Some hours don't belong to a single project—team meetings, training, travel between sites, administrative work. Decide upfront how to handle it: allocate proportionally, charge to a general overhead code, or exclude it. Be consistent about whatever you choose.
Incomplete data sets. If some people use the system religiously and others skip it, your project costs are understated for projects they worked on. You need compliance across the team.
Scope creep that isn't tracked separately. Projects rarely stay on scope. Client requests, rework, and late-stage changes all pile on hours. If possible, log these under a different project code so you can distinguish planned costs from scope-related overruns. This matters for both billing disputes and next-time pricing.
Frequently Asked Questions
How do I account for time that's not directly tied to a project? Team meetings, training, administration—these are real costs. Most businesses allocate them proportionally across active projects based on the percentage of total time spent. Others charge them to a general "overhead" code. Pick one method and stick with it. Consistency matters more than which approach you choose.
What if we bill hourly but employees are salaried? Divide the annual salary by the number of working hours in a year (typically 1,960–2,000 hours in the UK, depending on holidays). That's your base hourly rate. Then apply the fully loaded multiplier. You're calculating the true cost-to-business, not what you bill out at.
Should I include my own time? Yes, unless you literally do no billable work. Calculate your fully loaded hourly rate (even if you don't write yourself a paycheck) and log time against projects the same way employees do. This is the only way to know whether a project is actually profitable.
How often should I calculate project costs? After each project ends, at minimum. As you get more comfortable with the data, monthly or quarterly reviews of in-progress projects help you spot overruns early and reprice future similar work.
What if a project has multiple phases and we want to cost each separately? Use a different project code for each phase. This lets you compare the cost of design work versus implementation work versus support, and optimise how you resource each phase.
Can I use this to bill clients? If you bill time-and-materials, timesheet data feeds directly into invoicing. If you bill fixed-fee, use project costs to validate whether the fixed fee is realistic. Don't bill clients based on fully loaded rates that include your overhead multiplier; bill based on your time rates or agreed fees.
What's a "good" margin on project work? It depends on your industry, but most service businesses aim for 40–60% gross margin on labour (revenue minus labour cost, divided by revenue). If you're consistently below 40%, either your pricing is too low or your delivery is inefficient. Both are actionable insights.
How do I handle subcontractors? Log subcontractor hours as line items in the non-labour costs section (or as separate workers if you want a granular view). Their cost is whatever you pay them, not their fully loaded rate.
The Compounding Value of Better Data
Project costing is not a one-time calculation. It is the foundation of every business decision that follows: what to price, who to hire, what work to pursue, how to allocate resources.
The habit starts with consistent time recording against projects. The analysis compounds over months and years as you build a library of actual costs. Each project costed accurately makes the next estimate more reliable. Each margin analysis makes the next resource plan smarter.
For businesses that sell time—directly as hourly billing, or indirectly as fixed-fee delivery—this is not back-office. It is the mechanism that turns effort into profit. Without it, you are flying blind.
Start with a timesheet system that makes time recording easy. The rest follows naturally. Explore Relentify's integrated time tracking to see how project-level costing works in practice.