How to Calculate Hours Worked on a Night Shift — and Why Saturday's 8-Hour Shift Was Really 9
The first time I filled in a timesheet for a night shift, my spreadsheet told me I had worked negative 15 and a half hours. I'd clocked in at 22:00 and out at 06:30, typed "end minus start", and got −15:30. This weekend I nearly made the opposite mistake: on the night the clocks went back, my "8-hour" shift was actually 9 hours long, and the extra hour landed straight in overtime.
This guide is for anyone who works shifts, from warehouse and hospital staff to bar and security workers, and anyone who checks their own time card. You'll learn how to calculate hours worked from clock-in and clock-out times, how to handle unpaid breaks and shifts that cross midnight, and how to spot the daylight saving night that throws everything off by an hour.
⚠️ Disclaimer
This article is for informational purposes only and does not constitute legal or financial advice. Break and overtime rules vary by country, state and employer. Always check your contract or consult a qualified professional for your specific situation.
How Do You Calculate Hours Worked?
Hours worked is the time between clocking in and clocking out, minus any unpaid breaks. It's usually recorded in hours and minutes, then converted to decimal hours (for example, 7 hours 30 minutes becomes 7.5) so payroll can multiply it by an hourly rate.
The safest method is to turn every time into minutes after midnight, do the subtraction in minutes, and only convert back at the end.
Here's a normal day shift. Clock in at 08:45, which is 8 × 60 + 45 = 525 minutes. Clock out at 17:15, which is 1,035 minutes. The time between is 1,035 − 525 = 510 minutes. Take off a 30-minute unpaid lunch and you're left with 480 minutes, or 8 hours exactly.
Working in minutes avoids the most common slip of all: treating 7:45 as 7.45 hours. Clock time counts in sixties, so 45 minutes is 0.75 of an hour. I've written about how much that one mistake cost me in My Timesheet Said 40.60 Hours, and the Time to Decimal converter does the conversion for you.
Which Breaks Do You Subtract?
Not every break comes off your hours. In the United States, the Department of Labor's rules under the Fair Labor Standards Act (FLSA) treat short rest breaks and meal periods differently.
| Break type | US federal rule | Subtract it? |
|---|---|---|
| Rest break, 5–20 min | Counts as work time (29 CFR 785.18) | No |
| Meal break, usually 30+ min, fully relieved | Not work time (29 CFR 785.19) | Yes |
| Meal break where you must stay on call | Counts as work time | No |
Under US federal rules, rest breaks of 5 to 20 minutes are counted as hours worked and must be paid, while a bona fide meal period, usually 30 minutes or more with the employee fully relieved of duty, is not work time.
Other countries set the minimum break rather than the pay rule. In the UK, the Working Time Regulations 1998 give most adult workers a 20-minute uninterrupted rest break when they work more than 6 hours a day; whether it's paid depends on the contract. Australian break entitlements are usually set by the relevant modern award.
💡 Pro Tip
If your lunch keeps getting interrupted by calls or customers, note it on your time card. A meal break where you're still working isn't a break under US federal rules, so it shouldn't come off your hours.
How to Calculate Hours Worked Across Midnight
This is where my negative 15 and a half hours came from. When a shift crosses midnight, the clock-out time is a smaller number than the clock-in time, so a plain subtraction goes negative.
The fix is to add 24 hours (1,440 minutes) to the clock-out time whenever it's earlier than the clock-in time.
For a 22:00 to 06:30 shift: 06:30 is 390 minutes, plus 1,440 makes 1,830. Clock-in at 22:00 is 1,320 minutes. The time between is 1,830 − 1,320 = 510 minutes. Subtract a 30-minute meal break and you get 480 minutes, or 8 hours.
The Time Duration Calculator handles this automatically. Enter your clock-in, clock-out and unpaid break, and if the end is earlier than the start it treats the shift as running into the next day. For shifts longer than 24 hours, such as an on-call weekend, add the start and end dates as well.
What Happens on the Night the Clocks Change?
Daylight saving time is the practice of moving clocks forward one hour in spring and back one hour in autumn. In most of the United States, clocks went back at 2:00 a.m. on Sunday, November 1, 2026, so the hour from 1:00 to 2:00 a.m. happened twice.
That means anyone working overnight on Saturday, October 31 worked an extra hour that their clock-in and clock-out times don't show. A 22:00 to 06:30 shift looks like 8 hours 30 minutes on the clock, but 9 hours 30 minutes actually passed. After a 30-minute meal break, that's 9 hours worked, not 8.
| Change | Date (2026) | Effect on a night shift |
|---|---|---|
| US clocks go back | Sun, Nov 1 | Add 1 hour |
| UK clocks go back | Sun, Oct 25 | Add 1 hour |
| US clocks go forward | Sun, Mar 8 | Subtract 1 hour |
| NSW, Victoria clocks go forward | Sun, Oct 4 | Subtract 1 hour |
The FLSA requires covered employers to pay for hours actually worked, so the extra hour on a fall-back night counts, and it can push you over the 40-hour overtime threshold. In spring, the reverse happens: your clock shows an hour more than you really worked.
⚠️ Note
Most calculators, including ours, measure wall-clock time. On the night the clocks change, add one hour (fall back) or subtract one hour (spring forward) yourself. Many payroll systems adjust automatically, but it's worth checking your payslip for that week.
A Full Week of Night Shifts, Worked Out
Here's my week, starting with the Saturday night the clocks went back. My workweek runs Saturday to Friday, I earn $21 an hour, and overtime is 1.5× ($31.50) after 40 hours, the FLSA default.
| Shift starts | Clock in–out | Break | Hours worked |
|---|---|---|---|
| Sat, Oct 31 | 22:00–06:30 | 30 min | 9:00 (clocks went back) |
| Sun, Nov 1 | 22:00–06:30 | 30 min | 8:00 |
| Mon, Nov 2 | 22:00–07:15 | 30 min | 8:45 |
| Tue, Nov 3 | 21:45–06:30 | 30 min | 8:15 |
| Wed, Nov 4 | 22:00–06:45 | 45 min | 8:00 |
Using clock times only: 480 + 480 + 525 + 495 + 480 = 2,460 minutes, which is 41.00 hours. That's 40 regular hours and 1 overtime hour: $840.00 + $31.50 = $871.50.
Counting the extra daylight saving hour: 2,520 minutes, which is 42.00 hours. That's 40 regular hours and 2 overtime hours: $840.00 + $63.00 = $903.00.
The difference is $31.50 for a single hour, because it's an overtime hour. The same slip in the UK at £14 an hour is £14 at the basic rate, and in Australia at A$32 an hour it's A$32, before any shift or overtime loading.
Key Takeaway
Do every shift in minutes, add 24 hours when you cross midnight, subtract only unpaid meal breaks, and adjust by one hour on daylight saving nights. Convert to decimal hours once, at the end of the week.
Frequently Asked Questions
How many hours is 9 to 5 with a 30-minute lunch?
9:00 to 17:00 is 8 hours. Subtract a 30-minute unpaid lunch and you've worked 7 hours 30 minutes, which is 7.5 decimal hours.
How do I calculate hours worked for a shift that starts before midnight?
Add 24 hours to the clock-out time, then subtract the clock-in time. 22:00 to 06:00 is (6 + 24) − 22 = 8 hours.
Do 15-minute breaks come off my hours?
Not in the US. Rest breaks of 5 to 20 minutes count as hours worked under 29 CFR 785.18. Only bona fide meal periods, usually 30 minutes or more, are unpaid. Rules differ in other countries.
Which day does an overnight shift count toward for overtime?
It depends on how your employer defines the workweek. Under the FLSA, a workweek is a fixed, recurring 168-hour period chosen by the employer, so check where yours starts before splitting a shift across two weeks.
Should I convert each shift to decimals or the weekly total?
Add everything in minutes and convert once. Rounding each shift to two decimal places can drift by a minute or two over a week.
Try It Yourself
Calculating hours worked comes down to one subtraction in minutes, with three adjustments: add 24 hours across midnight, take off only unpaid meal breaks, and correct by an hour on the night the clocks change. Check your own shifts with the Time Duration Calculator, which handles overnight shifts and breaks and gives you decimal hours.
For a full week with rounding and overtime, use the Time Card Calculator, then see what your extra hours are worth with the Overtime Pay Calculator. For one-off conversions, the Time to Decimal converter turns hours and minutes into the number payroll expects.
