The lost time rate is the percentage of total available working time that is lost due to absence. It tells you how much productive capacity your workforce has forfeited to sickness, unplanned leave, or other authorised absences over a given period.
Unlike the absence rate — which measures the proportion of employees absent on a given day — the lost time rate quantifies the cumulative impact of absence across the entire workforce over time. It is a core metric for HR teams measuring the operational and financial cost of absence.
Key Takeaways
- The lost time rate measures the percentage of total available working hours lost to absence over a defined period.
- The formula is: (Total hours lost to absence ÷ Total available working hours) × 100.
- A lost time rate above 3% signals significant absence that warrants investigation.
- Lost time rate and absence rate measure different things — use both for a complete picture.
- Track the lost time rate monthly to identify trends, seasonality, and departmental patterns.
What Is the Lost Time Rate?
The lost time rate answers a simple question: out of all the hours your workforce was scheduled to work, how many were lost to absence?
This metric captures the full impact of absence — not just how many people were off, but how long they were off. An employee absent for three weeks has a far greater operational impact than one absent for a day, and the lost time rate reflects that.
How It Differs from Absence Rate
| Metric | What It Measures | Best For |
|---|---|---|
| Lost time rate | Percentage of total working hours lost to absence | Measuring cumulative impact and cost |
| Absence rate | Percentage of employees absent on a given day or period | Spotting workforce-wide patterns |
| Frequency rate | Number of absence episodes per employee | Identifying short-term absence problems |
| Bradford Factor | Impact of absence based on frequency and duration | Triggering absence management reviews |
You need more than one metric to understand absence fully. The lost time rate gives you the cost picture. The frequency rate tells you whether absence is driven by a few chronic cases or many short episodes.
The Lost Time Rate Formula
The formula is straightforward:
Lost Time Rate (%) = (Total hours lost to absence ÷ Total available working hours) × 100
Where:
- Total hours lost to absence = Sum of all hours absent across all employees during the period
- Total available working hours = Number of employees × Standard working hours per employee × Number of working days in the period
How to Calculate Lost Time Rate: Worked Example
Here is a practical example for a UK-based company.
| Data Point | Value |
|---|---|
| Number of employees | 50 |
| Standard working hours per week | 37.5 |
| Period measured | 4 weeks (one month) |
| Total available working hours | 50 × 37.5 × 4 = 7,500 hours |
| Total hours lost to absence | 225 hours |
Lost Time Rate = (225 ÷ 7,500) × 100 = 3.0%
A lost time rate of 3% means that for every 100 hours your workforce was scheduled to work, 3 were lost to absence. The CIPD Health and Wellbeing at Work survey (2024) reports the UK average lost time rate is approximately 2.6% — so this example sits slightly above average.
Interpreting the Result
| Lost Time Rate | Assessment | Action |
|---|---|---|
| Under 1.5% | Low | Maintain current practices |
| 1.5% – 2.5% | Average | Monitor trends and review policies |
| 2.5% – 4% | High | Investigate root causes, consider OH referrals |
| Over 4% | Very high | Urgent action needed — absence management review |
These are general benchmarks. What matters most is the trend over time and how your rate compares to your own historical data and industry norms.
How to Collect the Data
You need two data points for the calculation:
Total Hours Lost to Absence
For each employee, sum the hours they were absent during the period. This includes:
- Sickness absence (certified and uncertified)
- Authorised leave beyond statutory entitlement
- Unauthorised absence
- Any other absence that results in lost working hours
Do not include:
- Annual leave (planned, statutory entitlement)
- Public holidays
- Approved study leave or time off in lieu
The distinction matters. Annual leave is planned and expected. The lost time rate is about unplanned or extended absence that disrupts operations.
Total Available Working Hours
Multiply the number of employees by their standard contracted hours and the number of working days in the period. For part-time employees, use their actual contracted hours — do not use full-time hours and understate the available capacity.
Using Lost Time Rate for Action
A number without context is useless. The lost time rate becomes actionable when you break it down.
By Department
Compare lost time rates across departments. If one team consistently runs at 5% while the rest are at 2%, the problem is localised — possibly a management issue, workplace condition, or specific health risk.
By Absence Cause
Segment the data by cause. If 60% of lost time is due to musculoskeletal issues, the fix is ergonomic assessment, not a general absence policy tightening.
By Trend
Track monthly. A rising lost time rate signals a worsening problem. Seasonal spikes (e.g., winter flu) are normal, but a sustained increase requires investigation.
By Employee
Use the lost time rate alongside the Bradford Factor to identify individual cases that may need formal absence management. A high Bradford Factor score combined with a rising individual lost time rate is a clear signal.
Frequently Asked Questions
What is a good lost time rate?
A lost time rate under 2% is generally considered good. The UK average sits around 2.6% according to CIPD data. Rates above 3% indicate absence levels that are costing your organisation measurably and warrant investigation.
How is lost time rate different from absence rate?
The absence rate measures the proportion of employees absent on a given day. The lost time rate measures the total hours lost to absence over a period. An employee off for three weeks will barely affect the daily absence rate, but it will significantly increase the lost time rate.
How do we calculate lost time rate for part-time employees?
Use each employee’s actual contracted hours in the calculation. A part-time employee working 20 hours per week contributes 20 hours to the total available working hours, not 37.5. This ensures the rate accurately reflects your workforce’s actual capacity.
Should we include annual leave in the lost time rate?
No. Annual leave is a planned, contractual entitlement — not lost productive time. Including it would inflate the rate and obscure the actual problem. Only include unplanned or extended absence that disrupts operations.
How often should we calculate the lost time rate?
Monthly is the standard cadence. This gives you enough data points to spot trends without the noise of weekly fluctuations. Calculate it by department and organisation-wide, and review quarterly to assess whether absence management interventions are working.
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