What a labour-hour estimate is and why it beats a lump-sum guess
The unit-rate method rests on one observation: crews are far more consistent at rates than at totals. A drywall hanger who takes about 24 minutes to hang a sheet will take about 24 minutes a sheet whether the job has 80 sheets or 800. So you measure the quantity, multiply by the rate, and the hours fall out. The estimate is then auditable — anyone can challenge the quantity or the rate separately, which is exactly what you want in a bid review.
Three distinctions decide whether the number means anything.
Worker-hours versus crew-hours. A unit rate of 0.40 hours per sheet means 0.40 worker-hours. Three people working one hour burn three worker-hours. Confusing the two is the single most common error in labour estimating and it produces an answer off by the crew size — a factor of three or four, not a few percent.
Hours versus duration. Hours are a quantity of work; duration is how long that work occupies the calendar. Doubling the crew halves the duration and leaves the hours untouched, up to the point where people start queuing for the same wall. Beyond that, adding workers increases hours and may not shorten duration at all.
Wage versus cost. The wage on the pay stub is not what the hour costs you. Employer payroll taxes, workers compensation premium, general liability, benefits and paid leave all ride on top, and that load — the labour burden — is what turns a wage into a cost.
The formula, term by term
Hours are quantity times rate times a factor: H = Q × r × f.
Q is the takeoff quantity, in the same unit as the rate. Get this from measurement, not memory. Sheet counts come from a takeoff like the drywall sheet calculator; board quantities from the deck board calculator; concrete volumes from the concrete slab calculator.
r is the unit labour rate in worker-hours per unit. This is the one number in the whole calculation that must come from data. Divide the hours actually charged to a completed cost code by the quantity actually installed under it, and you have a rate that already contains your crews, your typical layout and your standard of finish. A published rate from a cost database is a reasonable starting point when you have no history, but it is a stranger's crew, not yours.
f is the productivity factor: a multiplier above 1.00 when conditions are worse than the conditions your rate came from, below 1.00 when they are better. Overhead work, tight access, occupied buildings, cold weather, small repetitive rooms, night shifts and heavy stop-start coordination all push it up. The discipline is to apply it once. If you have already picked a rate that reflects difficult work, do not then multiply it again — double counting difficulty is how bids get lost.
Crew days follow by division: D = H ÷ (n × s), where n is crew size and s is productive hours per shift. Use productive hours, not clock hours. A crew that clocks nine hours but loses time to mobilisation, breaks, toolbox talks and clean-up is not producing for nine hours, and an estimate built on clock hours runs late.
Cost is hours times the burdened rate, with a premium on the overtime share. The Fair Labor Standards Act requires non-exempt employees to be paid at least one and a half times their regular rate for hours worked beyond 40 in a workweek; the rules are set out in 29 CFR Part 778. This calculator applies the 1.5 multiplier to the fully burdened rate, which is the conservative treatment, because the largest components of burden — payroll taxes and workers compensation — are themselves assessed on gross wages and therefore rise with the premium.
Worked example: hanging 250 sheets of drywall
You have 250 sheets to hang. Your closed job costs put the crew at 0.40 worker-hours per sheet. Conditions are normal, so the productivity factor is 1.00. You will run three hangers on eight productive hours a day, five days a week. Average wage is $32.00 an hour and your burden is 35%.
- Labour hours. 250 sheets × 0.40 hr/sheet × 1.00 = 100 worker-hours.
- Crew-day capacity. 3 workers × 8 hr = 24 worker-hours per day.
- Crew days. 100 ÷ 24 = 4.17 crew days. Round up for scheduling: five days on site.
- Calendar weeks. 4.17 ÷ 5 = 0.83 weeks.
- Hours per worker. 100 ÷ 3 = 33.3 hours each — comfortably inside 40, so no overtime is required.
- Burdened rate. $32.00 × 1.35 = $43.20 per hour.
- Labour cost. 100 hr × $43.20 = $4,320.00.
- Cost per sheet. $4,320.00 ÷ 250 = $17.28 per sheet, labour only.
Now change one assumption. The ceilings are 10 feet, the rooms are small and cut-up, and you decide the factor is 1.25. Hours become 250 × 0.40 × 1.25 = 125, crew days become 125 ÷ 24 = 5.21, and cost becomes 125 × $43.20 = $5,400.00 — $1,080 more, or $4.32 a sheet. That is the whole value of carrying an explicit factor: the difficulty allowance is visible, arguable and adjustable instead of buried inside a rate nobody can audit.
And if 20 of those 100 hours land in overtime: 80 hr × $43.20 + 20 hr × $64.80 = $3,456 + $1,296 = $4,752. Twenty percent of the hours at time and a half adds ten percent to the cost.
How to read the result before you put it in a bid
Start with the cost per unit, not the total. It is the only output you can benchmark. If your file says drywall hanging has been landing at $16 to $18 a sheet and this estimate says $17.28, the estimate is behaving. If it says $31, either the quantity is wrong, the productivity factor is doing too much work, or the wage and burden are from a different crew than the one you will send.
Then read crew days against the schedule you have actually been given. Four and a fifth crew days is five days on site, because you cannot buy a fifth of a day of mobilisation. If the schedule allows three days, the honest options are more workers, longer shifts, or a later finish — and the crew-size table on this page shows what each of those buys. Note that it holds hours constant, which is optimistic at the top end: past the point where the work face is crowded, extra workers get in each other's way and the hours rise.
Watch the hours-per-worker output for a hidden overtime problem. If 100 hours are spread across three workers in one week, that is 33 hours each and no premium. Squeeze the same hours into two workers and it is 50 hours each — ten hours of overtime apiece under the FLSA, and a cost you did not carry.
Finally, remember what this is: direct field labour on one scope of work. It is not the job. Supervision, layout, protection, punch list, mobilisation, equipment, material handling and small tools all sit outside the unit rate unless you deliberately built them into it. Add them, then apply overhead and profit with the contractor markup vs margin calculator.
Hours, crew days and burdened cost for a 250-unit quantity
| Unit rate (hr/unit) | Labour hours | Crew days | Work weeks | Burdened cost | Cost per unit |
|---|---|---|---|---|---|
| 0.10 | 25.0 | 1.04 | 0.21 | $1,080 | $4.32 |
| 0.20 | 50.0 | 2.08 | 0.42 | $2,160 | $8.64 |
| 0.30 | 75.0 | 3.13 | 0.63 | $3,240 | $12.96 |
| 0.40 | 100.0 | 4.17 | 0.83 | $4,320 | $17.28 |
| 0.50 | 125.0 | 5.21 | 1.04 | $5,400 | $21.60 |
| 0.75 | 187.5 | 7.81 | 1.56 | $8,100 | $32.40 |
| 1.00 | 250.0 | 10.42 | 2.08 | $10,800 | $43.20 |
Cost per unit is simply the unit rate times the burdened hourly rate, which is why it scales exactly with the rate and is independent of quantity.
Building a labour burden you can defend
Burden is not a number you should guess, because most of it is on documents you already have. Work it out as a percentage of gross wages from your own payroll:
Employer FICA is fixed by statute at 7.65% of wages — 6.2% Social Security up to the annual wage base and 1.45% Medicare with no cap. IRS Publication 15 sets it out. Federal and state unemployment add a small further percentage that depends on your experience rating and your state's wage base. Workers compensation is the swing item: it is priced per $100 of payroll by classification code, and a roofing or steel-erection code costs a multiple of a carpentry code in the same state. General liability is often also rated on payroll. Then add whatever you provide in health insurance, retirement contributions, holiday and vacation pay, training and per diem.
Sum those, divide by gross wages, and you have a burden rate that belongs to your company rather than to a rule of thumb. It changes when your workers compensation experience modifier changes, so recalculate it every year at renewal. If you carry small tools and vehicle allowance inside burden rather than in overhead, be consistent about it, and be sure you are not also recovering them through your markup — recovering the same cost twice inflates a bid just as reliably as forgetting it once loses money.
Mistakes that make a labour estimate wrong
- Mixing worker-hours with crew-hours. A rate is per worker. Divide by crew size only when converting to duration, never when computing hours.
- Using clock hours as productive hours. Mobilisation, breaks, safety meetings and clean-up are real. Estimate on productive hours and the schedule holds.
- Double counting difficulty. Choosing a rate that already reflects tough conditions and then applying a productivity factor on top of it.
- Assuming duration scales without limit. Doubling the crew does not halve the duration once the work face is congested; it wastes hours.
- Pricing at the wage rate. An unburdened wage understates the cost of an hour by whatever your burden is — on the worked example above, by $11.20 an hour.
- Forgetting the FLSA threshold. Overtime is triggered by hours over 40 in a workweek, not by long days, so a compressed schedule can create premium pay you never carried.
- Leaving out non-installation labour. Layout, protection, material handling, stocking, clean-up and punch list are hours somebody works and somebody pays for.
- Never closing the loop. An estimate that is not compared with actual hours at the end of the job teaches you nothing and your unit rates never improve.
Where this method sits among the alternatives
The unit-rate approach used here is the most common in trade contracting because it needs only two inputs and both are auditable. Two neighbouring methods are worth knowing.
Crew-based daily output flips the arithmetic: instead of hours per unit, a published crew composition is credited with a daily output, and you divide quantity by that output to get crew days directly. Cost databases such as the RSMeans data are built this way. It handles mixed crews — two carpenters plus a labourer plus a lift — more naturally than a single blended rate, and converts to hours per unit by dividing crew hours per day by daily output.
Earned value is the method for tracking the work once it starts. You budget hours by cost code, record installed quantity and hours spent each week, and compare earned hours against actual. A productivity index below 1.00 tells you the job is burning hours faster than it is installing work, early enough to do something about it. Estimating and tracking with the same unit rates is what turns each job into better data for the next one.
For pricing the whole job rather than one scope, pair this with a parametric check from the construction cost per square foot calculator, and make sure the material side carries a proper order allowance from the construction waste factor calculator before the purchase orders go out.
Key terms
- Worker-hour (man-hour)
- One person working for one hour. The unit every labour rate is expressed in.
- Crew day
- One calendar day of one crew. Equal to crew size times productive shift hours in worker-hours.
- Unit labour rate
- Worker-hours required per unit of installed work. The inverse of productivity.
- Labour burden
- Employer costs that ride on top of wages: payroll taxes, workers compensation, liability insurance, benefits and paid leave, expressed as a percent of base wages.
- Productivity factor
- A multiplier applied to base hours to reflect conditions worse or better than those the unit rate came from.
- Regular rate of pay
- The FLSA term for the hourly figure that overtime is calculated from. It includes certain non-discretionary bonuses and shift differentials, not just the base wage.