In mining operations, ensuring the right number of personnel is available is critical for maintaining production targets while complying with roster and leave policies.
Unlike standard office environments, mining operations typically operate on a roster system. Employees alternate between working on site and taking scheduled time off, with additional entitlements such as periodic leave. Since every company may have different roster arrangements and HR policies, accurately calculating manpower requirements is essential to avoid understaffing or excessive headcount.
Why Calculate Manpower Requirement?
The objective is to determine how many employees are required to continuously cover operational positions after considering:
- Roster schedule
- Periodic leave
- Off-day cycle
- Attendance Rate (ATR)
- Other company-specific policies (such as induction days, mandatory training, or medical checks)
Without accounting for these factors, workforce planning can significantly underestimate the actual manpower required.
Variables Required
For this example, assume the following:
- Roster Cycle: 84 days
- Periodic Leave: 14 days
- Off Day Cycle: Every 14 days
- Attendance Rate (ATR): 95%
Step 1: Calculate Total Off Days Within One Roster Cycle
Formula:
Off Days = Roster Cycle ÷ Off Day Cycle
Example:
84 ÷ 14 = 6 off days
This means each employee receives 6 off days during one roster cycle.
Step 2: Calculate Off Days That Overlap with Periodic Leave
Some scheduled off days may occur during periodic leave and therefore should not be counted twice.
Formula:
Overlapping Off Days = ROUNDDOWN(Periodic Leave ÷ Off Day Cycle)
Example:
ROUNDDOWN(14 ÷ 14) = 1 day
If the result is a decimal (for example, 1.3), use the rounded-down value to represent the conservative assumption that only one off day overlaps with the leave period.
Step 3: Calculate Actual Off Days
Formula:
Actual Off Days = Total Off Days − Overlapping Off Days
Example:
6 − 1 = 5 days
Step 4: Calculate Effective Working Days
Formula:
Effective Working Days = Roster Cycle − Periodic Leave − Actual Off Days
Example:
84 − 14 − 5 = 65 days
If additional company policies reduce available working time, deduct them here.
For example, if employees must complete one day of safety induction after returning from periodic leave:
65 − 1 = 64 effective working days
Step 5: Apply Attendance Rate (ATR)
Employees are not expected to achieve 100% attendance due to various operational factors.
Formula:
Adjusted Effective Working Days = Effective Working Days × ATR
Example:
64 × 95% = 60.8 days
Step 6: Calculate the Manpower Ratio
Formula:
Manpower Ratio = Roster Cycle ÷ Adjusted Effective Working Days
Example:
84 ÷ 60.8 = 1.3816
This means that every operational position requires approximately 1.38 employees to maintain continuous coverage throughout the roster cycle.
Example Calculation
Suppose an operation has:
- 50 haul trucks
- 2 operating shifts
Total operational positions:
50 × 2 = 100 positions
Required manpower:
100 × 1.3816 = 138 employees
Therefore, at least 138 personnel are required to continuously cover 100 operational positions under the given roster arrangement.
Summary
A practical manpower requirement calculation should consider:
- Roster Cycle
- Periodic Leave
- Off Day Cycle
- Attendance Rate (ATR)
- Additional company-specific deductions (training, induction, medical examinations, etc.)
By incorporating these factors, organizations can estimate the minimum workforce required to sustain uninterrupted operations while complying with roster and leave policies.
Manpower Requirement Calculator
Estimate minimum manpower based on roster parameters.