Calculating work hours is based on a simple subtraction: end time minus start time, minus unpaid breaks. The method seems obvious, but the discrepancies between theoretical calculations and actual counts on a pay month generate the majority of disputes in companies. Which parts of the calculation concentrate the most errors, and how can they be identified before they appear on a payslip?
Minutes, hundredths, and decimals: where pay discrepancies arise
The conversion between minutes and hundredths of an hour is the technical point that most homemade Excel spreadsheets manage poorly. An employee who finishes at 5:45 PM after starting at 8:30 AM with a one-hour break has worked 8 hours and 15 minutes. Translated into decimal for payroll, this amounts to 8.25 hours, not 8.15.
The confusion arises from the fact that one minute does not equal one hundredth of an hour. 15 minutes correspond to 0.25 hours, not 0.15. The error, repeated over twenty working days, produces a significant discrepancy in the monthly total.
| Actual Minutes | Correct Decimal Value | Common Error (Raw Minutes) | Discrepancy per Occurrence |
|---|---|---|---|
| 10 min | 0.17 h | 0.10 h | +0.07 h |
| 15 min | 0.25 h | 0.15 h | +0.10 h |
| 20 min | 0.33 h | 0.20 h | +0.13 h |
| 30 min | 0.50 h | 0.30 h | +0.20 h |
| 45 min | 0.75 h | 0.45 h | +0.30 h |
Over a full month, an incorrect rounding of 30 minutes per day accumulates a discrepancy of several hours. A full-time employee whose quarter hours are consistently recorded as 0.15 instead of 0.25 loses the equivalent of two hours of monthly pay. A seemingly minor detail, a potential dispute.
To apply this conversion without error, the Ecostart site for calculating hours details a step-by-step method suitable for non-specialists.
Breaks and actual working time: what the calculation must include or exclude
The Labor Code defines actual working time as any period during which the employee is available to the employer without being able to freely attend to their own activities. This definition has a direct consequence on the calculation: a break during which the employee must remain reachable or on-site is not a true break in the legal sense.
In practice, three situations pose problems:
- The “on-site” lunch break where the employee remains available by phone or must monitor a position. If the employer requires availability, this time may be reclassified as actual working time.
- Changing clothes time when imposed by the job. It does not always appear in the count, but it must be compensated.
- Travel between two job sites on the same day. This is not rest time and must be accounted for, unlike the commute from home to work.
Deducting a break from the total without verifying if the employee was actually free remains the most common error in manual timekeeping files. It fuels a significant portion of labor disputes related to overtime.
Proof of hours worked: what case law requires in 2025
Many employers believe that a timekeeping software is sufficient to close any discussion. The legal reality is more nuanced. The Court of Cassation has reminded, notably in decisions from April 2, 2025, and September 24, 2025, that the burden of proof for overtime is shared between employee and employer.
In practical terms, an employee who provides a sufficiently precise record (dates, start and end times, breaks, overtime) compels the employer to provide their own control elements. A handwritten log kept daily may suffice on the employee’s side. However, on the employer’s side, a badge system or tracking software does not automatically serve as proof: the system must be reliable and tamper-proof.
A modifiable tool without traceability, poorly configured, or incomplete can be challenged in court, even if it is used daily in the company. This point changes the game for SMEs that rely on shared Excel sheets or unsecured time clocks.
Daily rest and overtime: two distinct calculations to be conducted in parallel
Checking that the weekly total does not exceed the legal duration of 35 hours per week is not enough. The minimum daily rest of 11 consecutive hours between two working days is a separate obligation. An employee who leaves their post at 10 PM and resumes at 7 AM the next day only benefits from 9 hours of rest, violating the legal threshold.
This control is not deducted from the total weekly hours. It requires comparing the end and start times of each consecutive day. A tracking table that adds hours without checking daily amplitude allows this type of non-compliance to slip through.
For employees on an annual contract in days, the logic is different but vigilance remains the same. The annual contract does not exempt the employer from monitoring the workload, the days and half-days worked, as well as compliance with rest times. A contract without real monitoring can be annulled by a judge, leading to a retroactive recalculation of hours based on common law.
The calculation of work hours is not just an arithmetic formula. The reliability of the result depends on decimal conversion, the legal qualification of breaks, and the traceability of the tracking system. A well-constructed spreadsheet that integrates these three parameters protects both the employee’s pay and the employer’s compliance.
