To calculate person months, we first need to understand what this term means. Person months are a unit of measurement used to express the amount of work done or the effort required to complete a task or project. It represents the number of months one person works full-time on a project.
The formula to calculate person months is straightforward:
Person Months = Total Effort in Hours / Hours in a Month (assuming a full-time worker)
A standard full-time schedule is often considered to be approximately 160 hours per month (assuming a 40-hour workweek). However, this can vary depending on the specific work environment, country, or organizational standards.
Example Calculation
Let’s say we want to calculate the person months for a project that requires 1,920 hours of effort.
- Determine the total effort in hours: 1,920 hours
- Determine the hours in a month for a full-time worker: 160 hours/month (for simplicity)
Person Months = Total Effort in Hours / Hours in a Month Person Months = 1,920 hours / 160 hours/month Person Months = 12 months
This means the project requires 12 months of effort from one person working full-time.
Considerations
- Part-time Work: If the person is not working full-time, you’ll need to adjust the hours in a month accordingly. For example, if someone works 20 hours a week (80 hours a month), you would use 80 hours/month in your calculation.
- Multiple Workers: If multiple people are working on the project, you would divide the total effort by the number of workers to find out how many person months each contributes, assuming they work the same amount of time.
- Variability in Work Hours: Different industries, countries, or companies may have different standards for what constitutes a full-time schedule. Always use the relevant standard hours for your specific context.
Calculation Tool
For those who prefer a more interactive approach, here’s a simple calculation tool you can use:
- Total Effort in Hours: _______
- Hours in a Month (for a full-time worker in your context): _______
Person Months = (Total Effort in Hours) / (Hours in a Month)
Just fill in the numbers and calculate.
Real-World Applications
Person months are particularly useful in project management for estimating the resources needed for a project, planning timelines, and allocating tasks to team members. It helps in understanding the scale of a project and in making informed decisions about staffing and resource allocation.
In summary, calculating person months involves dividing the total effort required for a project by the monthly hours worked by one full-time employee. This metric is crucial for project planning, ensuring that tasks are realistically timed and resourced.
