How to Calculate Work Hours
Calculating work hours comes down to three steps: find the span between your start and end time, subtract any unpaid break, and add the daily totals into a weekly figure. This guide walks through each step, including overnight shifts and decimal-hour conversion.
Start time and end time
For each day, record the time you started work and the time you finished. The difference between the two is the gross length of your shift before breaks are removed. If you work a normal daytime shift, the end time is simply later than the start time on the same day, so the span is end time minus start time.
Write times in a consistent 24-hour format when you can — for example, 09:00 and 17:30 — because it removes any ambiguity between morning and evening. If you use a 12-hour clock, always note AM or PM so a 7:00 start is not mistaken for a 19:00 start.
Subtracting unpaid breaks
Many shifts include an unpaid break, most commonly a lunch break. Because that time is not paid, it should be removed from the gross shift length to get your net work time. Enter the break as a number of minutes and subtract it from the shift span.
Paid rest breaks usually count as work time and should not be subtracted. Whether a particular break is paid or unpaid depends on your employer and your local rules, so check your employment terms rather than assuming.
Net work time = (end time − start time) − unpaid break (in minutes)
Shifts crossing midnight
Overnight shifts are the most common source of calculation mistakes. If your shift starts in the evening and ends after midnight, the end time is numerically smaller than the start time — for example, 22:00 to 06:00. Subtracting 06:00 from 22:00 would give a negative number, which is wrong.
The fix is to treat the end time as occurring on the following day. Add 24 hours to the end time before subtracting, or simply add 24 to the result whenever the end time is earlier than or equal to the start time. The WorkHoursHQ calculators do this automatically.
If end ≤ start, shift length = (end + 24 hours) − start
Adding daily hours into a weekly total
Once you have the net work time for each day, add the daily figures together to get your weekly total. It is easiest to work in minutes while adding, then convert back to hours and minutes at the end. This avoids rounding errors that creep in when you convert each day separately.
For overtime, most employers apply a weekly threshold — often 40 hours — and pay hours above that threshold at a higher rate. Total the week first, then split the total into regular hours and overtime hours against your threshold.
Weekly total = sum of daily net work times Overtime hours = max(weekly total − threshold, 0)
Converting minutes correctly
When you add up daily hours you often end up with a minutes value of 60 or more. Because 60 minutes equals one hour, any minutes total of 60 or above should be carried into the hours column. For example, 7 hours 90 minutes is really 8 hours 30 minutes.
Payroll systems and invoices usually want time in decimal hours rather than hours-and-minutes, because decimals are easier to multiply by an hourly rate. To convert, divide the minutes by 60 and add the result to the whole hours.
Decimal hours = hours + (minutes ÷ 60)
Decimal hours
Decimal hours express the minutes part of a time as a fraction of an hour. Thirty minutes is 0.50 hours, not 0.30 — a mistake people make often. Forty-five minutes is 0.75 hours, and fifteen minutes is 0.25 hours. See the Decimal Hours Explained guide for the full breakdown.
Worked example
You work Monday to Friday, 09:00 to 17:00, with a 30-minute unpaid lunch each day. Each day is 8 hours minus 30 minutes, so 7 hours 30 minutes. Across 5 days the week totals 37 hours 30 minutes. In decimal form that is 37.50 hours (30 ÷ 60 = 0.50). At $20 per hour with no overtime, gross pay is 37.50 × $20 = $750.00.