How It Works
The hours calculator computes the elapsed time between two clock readings and subtracts any break time. The core formula is:
Work Hours = (End Time - Start Time) - Break Minutes
Both times are first converted to minutes since midnight. If the end time is numerically smaller than the start time (indicating an overnight shift), 1,440 minutes (24 hours) are added to the end time before subtraction. The break is then deducted from the gross elapsed minutes, and the result is converted to both hours:minutes and decimal formats.
In MathML notation:
The decimal conversion divides total net minutes by 60. For example, 7 hours and 45 minutes becomes 465 minutes, and 465 / 60 = 7.75 decimal hours. This decimal form is what most payroll systems require when multiplying by an hourly wage.
Variable Definitions
Start Time is the clock reading when you begin work. This should reflect the actual moment you start performing duties, not the time you arrive at the building or park your car. Most time-tracking systems record this to the nearest minute. If your employer rounds to the nearest quarter hour, you may see slight differences between this calculator and your official timesheet. Typical start times for day shifts range from 6:00 AM to 9:00 AM, while evening shifts commonly begin between 2:00 PM and 4:00 PM. A common mistake is entering PM times incorrectly -- if you start at 2:30 PM, make sure your time picker shows 14:30 in 24-hour format.
End Time is the clock reading when you stop working. If you end after midnight (for example, a shift from 10 PM to 6 AM), enter the end time as 06:00. The calculator detects that 06:00 is earlier than 22:00 and automatically adds 24 hours. This allows correct computation of overnight, graveyard, and swing shifts without any special configuration. A common mistake is forgetting to account for daylight saving time transitions, which can add or subtract one hour on transition days.
Break Minutes represents the total number of minutes of unpaid break during the shift. Federal law (FLSA) does not require meal or rest breaks, but many states mandate a 30-minute meal break for shifts over a certain length (commonly 5 or 6 hours). Short rest breaks of 5 to 20 minutes are generally considered compensable work time under federal law. Enter only the unpaid portion. For example, if you took a 30-minute lunch and two 10-minute paid rest breaks, enter 30 (not 50). Typical values are 0, 15, 30, or 60 minutes. Setting this incorrectly is the most common source of timesheet discrepancies.
Edge Cases and Advanced Scenarios
Overnight and graveyard shifts: When the end time is earlier than the start time, the calculator assumes the shift crosses midnight exactly once. For example, 11:00 PM to 7:00 AM computes as (7:00 + 24:00) - 23:00 = 8 hours gross. If your shift spans more than 24 hours (a rare but possible scenario for on-call medical staff), this single-crossing assumption will not produce the correct result. In that case, break the calculation into two segments or manually add 24 hours to the result.
Multiple breaks throughout the day: The break field accepts a single total number. If you took a 30-minute lunch, a 15-minute coffee break, and a 10-minute rest, enter 55 as the total break minutes (assuming all three were unpaid). The calculator does not track individual break start and end times -- it simply subtracts the total from the gross elapsed time. For more granular tracking, consider using this calculator once per work segment and summing the results.
Daylight saving time transitions: On the day clocks "spring forward," a shift from 1:00 AM to 3:00 AM is actually only 1 hour of elapsed time, not 2. On the "fall back" day, the same span is 3 hours. This calculator uses clock time only and does not account for DST. If your shift spans a DST transition, manually adjust the result by adding or subtracting one hour as appropriate.
What to Do with Your Result
Verify against your official timesheet. Compare the decimal hours from this calculator to what your employer's system records. Small discrepancies (a few minutes) often result from rounding rules. If the difference is more than 15 minutes, investigate whether break times or clock-in/out times were recorded differently.
Calculate your gross pay. Multiply the decimal hours by your hourly rate to estimate earnings before taxes. For example, 7.75 hours at $22.50/hour = $174.38 gross pay. This is useful for freelancers who invoice by the hour or employees who want to project their paycheck.
Track weekly totals for overtime. Under the FLSA, non-exempt employees earn 1.5x pay for hours exceeding 40 in a workweek. Use this calculator daily and keep a running total. If you hit 40 hours by Thursday, every hour on Friday is overtime. Some states (like California) also require daily overtime after 8 hours.
Plan your schedule around target hours. If you need to work exactly 7.5 hours and want to take a 45-minute lunch, work backward: 7.5 hours + 0.75 hours break = 8.25 hours total span. Starting at 8:00 AM means you should plan to leave at 4:15 PM.