How to Calculate Hours Worked: Breaks, Decimals, Overtime
Calculate hours worked from clock-in and clock-out times: subtract unpaid breaks, handle overnight shifts, convert to decimal hours and work out overtime.
By Awais, Founder and editor-in-chiefPublished
To calculate hours worked, subtract the start time from the end time, then subtract any unpaid break. Someone who works from 8:52 a.m. to 5:31 p.m. with a 30-minute unpaid lunch has worked 8 hours 39 minutes, minus 30 minutes, which is 8 hours 9 minutes, or 8.15 hours in decimal form for payroll.
The two steps people get wrong are converting minutes to decimal hours and handling shifts that cross midnight. Both are covered below, along with a full weekly time card and overtime. The hours calculator does one shift at a time; the time card calculator does a whole week with overtime and pay.
Step 1: Convert to 24-hour time
Subtraction is easiest in 24-hour time. Add 12 to any p.m. hour except 12 p.m.:
| 12-hour | 24-hour |
|---|---|
| 8:52 a.m. | 08:52 |
| 12:15 p.m. | 12:15 |
| 5:31 p.m. | 17:31 |
| 11:45 p.m. | 23:45 |
| 12:10 a.m. | 00:10 |
Step 2: Subtract start from end
Subtract the minutes first. If the end minutes are smaller, borrow an hour (60 minutes).
Example: 17:31 − 08:52.
- Minutes: 31 − 52 can’t be done, so borrow: 91 − 52 = 39 minutes, and the end hour becomes 16.
- Hours: 16 − 8 = 8 hours.
- Result: 8 hours 39 minutes.
An easier way is to turn both times into minutes after midnight: 17:31 = 1,051 minutes; 08:52 = 532 minutes; 1,051 − 532 = 519 minutes = 8 h 39 min.
Step 3: Subtract unpaid breaks
Subtract meal breaks that are unpaid. 519 − 30 = 489 minutes = 8 h 9 min.
In the US, the Fair Labor Standards Act (FLSA) treats short rest breaks of about 5 to 20 minutes as paid working time. Bona fide meal periods, usually 30 minutes or more, when you’re completely relieved from duty, can be unpaid. If you have to answer phones or watch a machine during lunch, it counts as work. Other countries and some US states have their own break rules, so check your contract and local law.
Step 4: Convert to decimal hours
Payroll multiplies hours by a pay rate, so it needs hours as a decimal. Divide the minutes by 60:
8 h 9 min = 8 + 9 ÷ 60 = 8 + 0.15 = 8.15 hours.
| Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|
| 5 | 0.08 | 35 | 0.58 |
| 10 | 0.17 | 40 | 0.67 |
| 15 | 0.25 | 45 | 0.75 |
| 20 | 0.33 | 50 | 0.83 |
| 25 | 0.42 | 55 | 0.92 |
| 30 | 0.50 | 60 | 1.00 |
The classic mistake: writing 8 hours 9 minutes as “8.09”. That’s 8 and 9 hundredths of an hour, about 8 hours 5 minutes. On a $22 hourly rate, the difference is small for one day but adds up across a payroll. The same mistake on 7 h 45 min (“7.45” instead of 7.75) loses 18 minutes of pay.
A full weekly time card
| Day | In | Out | Unpaid break | Hours worked | Decimal |
|---|---|---|---|---|---|
| Mon | 8:52 | 17:31 | 30 min | 8:09 | 8.15 |
| Tue | 9:05 | 18:10 | 45 min | 8:20 | 8.33 |
| Wed | 8:58 | 17:02 | 30 min | 7:34 | 7.57 |
| Thu | 9:00 | 19:15 | 30 min | 9:45 | 9.75 |
| Fri | 8:45 | 16:30 | 30 min | 7:15 | 7.25 |
| Total | 41:03 | 41.05 |
Add the minutes first (2,463 minutes in total), then convert once at the end: 2,463 ÷ 60 = 41.05 hours. Adding rounded daily decimals can be off by a hundredth or two.
Overtime
Under the FLSA, non-exempt employees in the US must be paid at least one and a half times their regular rate for hours over 40 in a workweek. Overtime is based on the week, not the day, under federal law; a few states, such as California, also have daily overtime rules.
With a $22 hourly rate and 41.05 hours:
| Hours | Rate | Pay | |
|---|---|---|---|
| Regular | 40.00 | $22.00 | $880.00 |
| Overtime | 1.05 | $33.00 | $34.65 |
| Gross pay | 41.05 | $914.65 |
The time card calculator applies the 40-hour rule automatically. To see what’s left after tax, use the paycheck calculator.
Outside the US, overtime rules differ. Many countries set a weekly limit and an overtime premium in law or in the employment contract, so check yours.
Overnight shifts
When a shift crosses midnight, the end time is “smaller” than the start time. Add 24 hours to the end time before subtracting.
Example: a night shift from 22:00 to 06:30 with a 30-minute unpaid break.
- 06:30 + 24:00 = 30:30
- 30:30 − 22:00 = 8 h 30 min
- Minus break: 8 h 00 min (8.00 hours)
For payroll, the hours usually belong to the day the shift started, but employers can set their own rule as long as it’s consistent. The time calculator also adds and subtracts times across midnight.
Rounding punch times
Some employers round clock-in and clock-out times to the nearest 5 minutes, tenth of an hour (6 minutes) or quarter hour (15 minutes). US regulations allow this only if it averages out over time and doesn’t consistently favour the employer. For example, rounding to the nearest quarter hour means 8:07 becomes 8:00 but 8:08 becomes 8:15.
If you’re an employee and your time is always rounded down, keep your own record of actual times. The Department of Labor’s guidance on hours worked explains what counts.
Quick checks
- Total under 24 hours per day? If not, you’ve added rather than subtracted somewhere.
- Minutes under 60? A total like 8:75 means a carrying mistake; it should be 9:15 (9.25 hours).
- Breaks subtracted once? It’s easy to subtract lunch twice when the clock-out for lunch is already recorded.
- Overtime by week? Under federal US rules, a 10-hour day isn’t overtime by itself; only the weekly total over 40 counts.
FAQ
How do I calculate hours worked in a day?
Subtract the clock-in time from the clock-out time, then subtract any unpaid break. Convert the minutes to decimals by dividing by 60 if you need decimal hours.
How do I convert minutes to decimal hours?
Divide the minutes by 60. 15 minutes is 0.25, 30 minutes is 0.5, 45 minutes is 0.75 and 20 minutes is 0.33.
Are breaks counted as hours worked?
Under US federal law, short breaks of about 5 to 20 minutes are paid and counted. Meal breaks of 30 minutes or more, where you’re fully relieved from work, can be unpaid. Rules elsewhere vary.
How is overtime calculated?
In the US, hours over 40 in a workweek are paid at 1.5 times the regular rate for non-exempt employees. Multiply overtime hours by the hourly rate and by 1.5, and add that to pay for the first 40 hours.