Sometimes a very rough high level direct labour man-hour calculation is needed for initial planning, site man-power resourcing, camp sizing or other contracting strategy discussions.
Key quantities for the project could be utilised to quickly estimate the overall direct labour man-hours. Detailed Material take-offs (MTOs) would generally be produced during the FEED (Front End Engineering Design) stage as an input to the detailed estimate. The below high level key quantities could easily be extracted from the MTOs. (If the MTOs are not prepared, then rough quantities from similar project could be used).
The following rough “hours/ key quantity” could be utilised to calculate the total direct man-hours for a major onshore project, based on all site fabrication and installation. Any pre-fabrication in a shop will increase productivity and reduce total direct hours.
This might also be helpful for cross-checking if the overall man-hours being calculated by the estimating team is in the right ball park.
Key Quantities & Direct Labour Hours (Excel Version) – free estimating resource
These rough “Hours / Key Qty” are very much high level anecdotal numbers to just help with a quick calculation of the total direct labour hours. The estimated hours for individual projects will depend on several design parameters, plot layout, location, labour productivity and many other factors. Individual estimators on the project should still do the more detailed work. If no estimating resource is available then this can be used as a rough guide.
Indirect hours could be calculated as a percentage of the direct hours, roughly say 30-40% of the direct hours.
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