On a construction site, a site manager records 7 h 45 min for a team. The payroll service reads 7.45 and calculates the gross salary based on this. Result: a difference of a few euros per day, which accumulates over an entire month.
This type of confusion between sexagesimal format and decimal format still fuels disputes over pay slips. Switching to hundredths of an hour at work addresses this issue at the source, because time becomes a number directly usable by a calculator or spreadsheet.
Conversion errors between minutes and hundredths: what causes issues on the ground
The most common trap can be summed up in one line: 7 h 30 is not 7.30 but 7.50 in decimal. Thirty minutes represent half an hour, so 0.50, not 0.30. When manually handling time entries or using a poorly configured spreadsheet, this confusion generates discrepancies on each pay line.
Feedback varies on this point, but most managers who switch to the centesimal format report that salary calculation errors decrease from the very first month. The reason is mechanical: in decimal base, multiplying a number of hours by an hourly rate works without intermediate steps.
Let’s take a concrete case. An employee works 7 h 45 min during the day. In hundredths, 45 minutes divided by 60 gives 0.75. We get 7.75 hours. Multiplied by the hourly rate, the result directly converts to euros, without any additional conversion. This is precisely why using hundredths of an hour at work is essential in payroll and project management services.
Conversion formula for minutes to hundredths and practical benchmarks
The formula can be summed up in three words: minutes divided by 60. This is the only operation needed to convert from the classic hourly format to decimal format. No secret coefficient, no mandatory correspondence table.
Some benchmarks speed up daily reading:
- 15 minutes = 0.25 hour (a quarter of an hour, the most intuitive)
- 30 minutes = 0.50 hour (half, often well understood)
- 45 minutes = 0.75 hour (three quarters, the least problematic)
- 10 minutes = 0.17 hour (common rounding, a frequent source of micro-discrepancies)
- 20 minutes = 0.33 hour (one third, a recurring value in time tracking)
With these five values memorized, most cases encountered in daily time tracking are covered. For intermediate durations (37 min, 52 min), dividing by 60 remains the reflex to keep.
Why the sexagesimal base complicates duration calculations
Our hourly system inherited from the Babylonians divides the hour into 60 minutes. This is convenient for reading a clock but incompatible with standard arithmetic operations. Adding 3 h 50 and 2 h 40 in base 60 gives 6 h 30, not 6.90. The decimal format eliminates this mental gymnastics and aligns time with the same system as euros, percentages, and hourly rates.
Dual display hh:mm and decimal: the method that reduces payroll disputes
A practice that has been generalizing for a few years is to keep two separate columns on time tracking reports. The first displays time in hours and minutes, immediately readable by the employee. The second translates this same time into decimal format, usable by the payroll service to calculate overtime, bonuses, and caps.
This dual format serves two distinct functions. The employee checks their hours without having to convert anything. The payroll manager works with decimal values that can be added, multiplied, and integrated into software without the risk of rounding errors.
Single rounding at the end of the period: what SaaS tools change
Online time tracking solutions have begun to modify their calculation logic. Instead of rounding each time entry individually (which accumulates micro-discrepancies over the month), several tools now apply a single rounding at the end of the period. The gross time remains stored with its maximum precision, and only the monthly total is rounded.
This approach limits discrepancies between the time actually worked and the time paid. In a team of several dozen people, the cumulative difference between daily rounding and monthly rounding can represent a significant fraction of an hour.
Configuring a spreadsheet for automatic conversion to hundredths
Many companies do not use dedicated payroll software for daily tracking. The spreadsheet remains the tool on the ground, and its configuration determines the reliability of the data transmitted to the payroll service.
The basic manipulation consists of formatting the cells as decimal numbers rather than in hour format. In a standard spreadsheet, a cell displaying 7:30 actually stores a fraction of a day (0.3125 for 7 h 30). To obtain the decimal value in hours, this fraction is multiplied by 24. The result, 7.50, is directly usable for salary calculation.
- Column A: start time in hh:mm format
- Column B: end time in hh:mm format
- Column C: gross duration (B – A), formatted in hh:mm for visual verification
- Column D: duration in decimal, formula = (B – A) * 24, formatted as a number with two decimal places
This setup reproduces the principle of dual display. The employee or team leader reads column C. The manager exports column D to the payroll software.
Common error to avoid in the spreadsheet
Entering 7.30 in a cell thinking it represents 7 h 30 is the most common mistake. The spreadsheet interprets 7.30 as seven hours and thirty hundredths, or 7 h 18 min. Always enter in hh:mm format and then let the formula convert. This reflex eliminates the main source of error even before the data reaches payroll.
Converting to hundredths is not an administrative whim. It is a technical choice that aligns working time with the decimal system used everywhere else in accounting. The real gain is measured less in abstract productivity than in hours of verification and correction saved each month, both for employees and managers.
