The reliable method keeps gross shift time, break time, and worked time separate. That makes the total easy to audit when one break changes.
Find gross shift minutes first
For a 09:00–17:30 shift, the gross duration is 8 hours 30 minutes, or 510 minutes. Keeping the arithmetic in integer minutes avoids rounding while times are being combined.
Subtract only the entered break
A 30-minute unpaid break changes 510 gross minutes into 480 worked minutes, displayed as 8:00. WorkHours does not invent a default break or decide whether a break should be paid.
Add worked minutes, then format
Combine the net minutes from all shifts before converting the final value to H:MM or decimal hours. This preserves an exact minute total. Confirm workplace break rules separately because the calculator applies only the values entered.