I multiplied the decimal hours by the rate myself and got 45 halalas less than the calculator. Which is right?
The calculator is. The decimal column is rounded to two places for display only: 7 hours 20 minutes is 7.3333 hours and shows as 7.33. Multiply 7.33 by the rate and you lose a sliver of every day. The calculator multiplies the exact total minutes by the rate and rounds once, at the end.
Where the 45 halalas went
An employee works three days, each from 09:00 to 16:20 with no break, at 45.5 SAR an hour. Each row shows 7:20 in the hours column and 7.33 in the decimal column. The usual hand calculation: 7.33 x 3 x 45.5 = 1,000.545, so about 1,000.55 SAR.
The calculator shows 1,001.00 SAR, because it never uses 7.33 in the arithmetic. It adds the minutes: 440 x 3 = 1,320 minutes, exactly 22:00 hours. Then 22 x 45.5 = 1,001, with no rounding on the way.
The whole gap is the dropped decimal. 7.33 is short of 7.3333 by about a third of a hundredth of an hour, a fifth of a minute each day. Over three days that is about 0.01 hours, and at 45.5 an hour roughly 45 halalas. Small, but it compounds: over six days the hand figure is 2,001.09 instead of 2,002.00, 91 halalas short.
When the gap appears and when it does not
- It does not appear when the minutes are a clean fraction of an hour: 15, 30 and 45 minutes become exactly .25, .50 and .75.
- It appears with minutes that do not divide cleanly by 60, such as 20, 40, 10 and 50, because their decimals run on.
- It grows with a higher hourly rate, with more days, and with more staff if you do the whole team by hand this way.
A second, much smaller gap: adding daily pay
There is another reason figures can differ, far smaller. Work out each day's pay on its own and round it: 7:20 at 45.5 is 333.67 SAR a day. Three days at that rounded figure make 1,001.01, one halala above the total. That is why the calculator notes that adding up per-day amounts by hand can differ from the total by one unit in the last place. The total on screen is rounded only once, so it is the closest to the true value.
How to check it yourself
- Open the Timesheet calculator, enter the days, and read the total hours in h:mm, here 22:00.
- Turn the total into hours: whole hours plus minutes divided by 60. 22:00 is exactly 22 hours.
- Multiply that by the rate. If the minutes are not clean, such as 36:40, keep the full fraction, 36 + 40 / 60, and do not round before multiplying.
- Round the result once to the halala. It should match the calculator's total pay.
If your payroll system asks for decimal hours, give it the total hours from the summary rather than the sum of the decimal column, and use the calculator's amount when you compare.
Common questions
Why not show the decimal column with four places, then?
Two places are easier to read and compare. The column is for display; the arithmetic does not rely on it.
Does the calculator round minutes?
No, never. Every minute counts as it is; the only rounding is on the final amount.
Which figure goes on the payslip?
Total pay as the calculator shows it, because it is worked out from whole minutes.