Labour Days and Crew Calculator
Man-days, crew size and labour cost from output rates.
Quick answer
With the default inputs: Quantity 100 · Output per man-day 8 per man-day · Planned duration 10 days etc.Total man-days 12.5 man-days
Edit the inputs below to recalculate.Inputs
Result
Total man-days
12.5man-days
| Quantity | 100.00 |
| Output per man-day | 8.00per man-day |
| Crew required (exact) | 1.32persons |
| Crew required (rounded up) | 2persons |
| Duration with that crew | 6.6days |
| Labour cost | 4375CNY |
| Output per man-day | 8.00per man-day |
| Man-days per unit | 0.1250man-days |
Output rates come from local estimating standards or your own records, and vary 30% or more between regions and crews. Dividing by attendance is essential: 100 man-days needed, but ten men at 95% attendance deliver only 95. Rounding the crew up changes the duration, so check the result against the programme.
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Man-days | quantity ÷ output per man-day |
| Crew | man-days ÷ (duration × attendance) |
| Rounding | round up to a whole person |
| Actual duration | man-days ÷ (crew × attendance) |
| Cost | man-days × rate |
| Unit labour | man-days ÷ quantity |
100 m² at 8 m² per man-day over 10 days at 95% attendance and 350 per man-day: 12.5 man-days, 1.32 people rounded to 2, an actual 6.6 days and 4375 in labour.
How to work it out
- Total labour days = quantity ÷ output norm, where the output norm is how much one labour day produces, say 8 m³ of brickwork.
- Confirm which norm you have: output and time norms are reciprocals. A time norm of 0.125 labour days per m³ is an output of 8 m³ per day, and mixing them is a 64-fold error.
- Labour required = total labour days ÷ (programme duration × attendance rate). Attendance covers sickness and leave, normally 90-95%.
- Labour cost = total labour days × daily rate, banded by general, skilled and specialist.
- Sanity-check the headcount: a work face holds a limited number of people, so a computed 200 on a 50 m² face means the programme is unrealistic and needs more faces or more time.
Where it goes wrong
- Confusing output and time norms — 8 m³ per day against 0.125 days per m³, and getting the direction wrong changes the answer 64-fold.
- Ignoring attendance — 100 on the books is not 100 on site every day, and assuming full attendance loses the programme.
- Ignoring productive days — rain, wind, heat and inspections mean outdoor work typically gets 75-85% of calendar days.
- Sizing the crew without the work face — a masonry face takes 15-20 people at once, so a computed 100 is theoretical.
Material and cost
General labour 200-300 CNY per day, skilled trades 350-500, specialists 500-800. Labour is normally 20-30% of construction cost with materials included.
On site
- Output norms vary by region and contractor; your own historical data beats the published norm, which is only a reference.
- Distinguish day rate from measured rate: measured work is 20-30% more productive but quality varies more.
- Crashing is not linear — doubling the crew typically buys 60% more output because the face is congested and materials lag.
Basis
- GB 50500-2013 Code of bills of quantities and valuation for construction works
- GB/T 50502-2009 Code for design of construction organisation
- National consumption quotas for building and decoration works (MOHURD)
FAQ
Are output and time standards reciprocals?
Yes. The output rate says how much one man-day completes, in m² per man-day; the time standard says how many man-days a unit needs, in man-days per m². 8 m² per man-day is 0.125 man-days per m². Quotes read better in time standards, crew planning in output rates — take the reciprocal.
Why does 1.32 people become a crew of 2?
Because people do not split. Rounding up cuts the duration to 6.6 days but leaves idle time; one person alone takes 13.2 days and misses the date. In practice you crew one and add help on the critical days, or borrow from an adjacent trade. The decision compares the deadline against the cost of idle time, not the arithmetic.
Is man-days times rate an accurate labour cost?
Only as a baseline. Real settlement works three ways: daywork against attendance, piecework against measured quantity, and supply-and-fix. Piecework rates already carry the efficiency risk and typically run 15-30% above the computed man-day cost. Estimate the floor from standards, quote from piecework rates, and the gap is your margin.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Labour Days and Crew Calculator. 2026-10-25. https://jianzhujisuan.com/en/labor-productivity
Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.