Free Shift Length Calculator
Find the exact length of a day, night or overnight shift. Enter your shift start and finish, account for breaks, and see the complete shift duration alongside credited hours and decimal time. Advanced options also help you calculate required clock-in or clock-out times.
Calculate your shift length
Enter the beginning and end of one shift. Your result updates automatically.
Enter the hours you want to work, excluding unpaid breaks. The calculator finds the missing shift boundary.
Unpaid breaks reduce credited hours, but not the full elapsed shift length. Paid breaks are included in credited hours.
One-shift calculation · No automatic time rounding · Clear validation for invalid inputs.
Advanced Options & Exports Reverse time planning, daylight saving, extra breaks, saved shifts and downloads ⌄
Formula and shift validation
Shift duration formula
Elapsed shift duration minus unpaid breaks equals credited shift hours.
Time boundary review
Browser-local autosave is available when permitted. The tool calculates shift durations; it does not verify attendance or determine legal working-time requirements.
Calculate a single shift in three straightforward steps.
Measure the complete time between shift boundaries, inspect break-adjusted hours, and review any unusual overnight or daylight-saving conditions.
Choose shift boundaries
Enter the start and finish dates and times. A following-day finish handles ordinary overnight work.
Record break durations
Enter unpaid and paid breaks separately. Additional break types are available under Advanced Options.
Read the shift duration
See the full elapsed shift length first, with credited hours, decimal hours and other figures underneath.
A shift's full duration and its credited hours are not always the same.
A scheduled shift from 9:00 AM to 5:30 PM has an elapsed duration of eight hours and thirty minutes. With thirty minutes of unpaid lunch, its credited work duration is eight hours.
The Shift Length Calculator places the complete shift interval first. Break-adjusted figures appear separately, so an unpaid break does not change the meaning of the scheduled shift's start-to-finish span.
One continuous 8-hour-30-minute interval
Illustrative example; your live result is shown in the calculator.
Understand every boundary behind your shift duration.
Learn the difference between elapsed and credited hours, calculate night shifts and long duty periods, work with break deductions, and identify situations where daylight-saving changes affect actual elapsed time.
How to calculate the length of a shift
Shift length is the time span between a scheduled starting boundary and finishing boundary. For work occurring on one date, subtract the starting clock time from the finishing clock time. If the shift continues past midnight, account for the appropriate following-day date.
Suppose a shift begins at 7:15 AM and finishes at 3:45 PM. The interval is eight hours and thirty minutes, equivalent to 510 elapsed minutes. If the shift includes thirty unpaid minutes, the credited working duration is eight hours.
These are two distinct results. Elapsed shift length = finish boundary − start boundary. Credited duration is then calculated by subtracting the unpaid break minutes from that elapsed length. Paid breaks remain within the credited figure.
The calculator measures time in whole minutes. Decimal representations are derived afterward, rather than being used as rounded intermediate values.
Calculate night shifts that cross midnight
An overnight shift crosses from one calendar date into the next. For example, a shift starting Monday at 10:00 PM and ending Tuesday at 6:00 AM spans eight hours when no daylight-saving change occurs.
The finish reading, 06:00, is smaller than the starting reading, 22:00. Without its date, this can be mistaken for a negative duration. Entering the actual end date removes that ambiguity.
Use the calculator's Set next day shortcut for a normal overnight shift. If the shift spans more than one calendar day, use the date fields directly.
A thirty-minute unpaid break does not make this an eight-hour-fifteen-minute shift; it remains an eight-hour scheduled interval with seven hours and thirty minutes of credited time.
Why wall-clock hours can differ from actual elapsed time
Clocks sometimes move forward or backward for daylight-saving time. During a spring transition, a local clock hour can disappear. During an autumn transition, an hour can happen twice.
Consider London on 29 March 2026. Its clocks move forward from 1:00 AM to 2:00 AM. A shift starting at 12:30 AM and finishing at 3:30 AM displays a three-hour wall-clock difference, but only two actual hours elapse.
In the autumn transition on 25 October 2026, a local time such as 1:30 AM occurs twice. The two occurrences refer to different instants. Choosing the earlier or later occurrence matters for calculating actual elapsed shift time.
The advanced mode uses an IANA time zone and verifies that entered local clock readings exist. It requires a choice for repeated hours and rejects nonexistent local times rather than silently replacing them.
Actual elapsed minutes are a mathematical result. How an organization treats clock changes for compensation or scheduled paid hours may require separate policies or employment-law guidance.
Find a required clock-out or clock-in time
Sometimes the required working duration is already known. For example, you may need eight credited hours but only know when the shift starts.
In that case, calculate the full span by adding unpaid breaks to the credited target. If the target is eight credited hours with a thirty-minute unpaid lunch, the full shift must cover eight hours and thirty minutes.
Starting at 8:30 AM gives a projected clock-out of 5:00 PM. Conversely, if the required finish is 6:00 PM and an eight-hour credited target includes forty-five unpaid minutes, the start must be 9:15 AM.
The advanced reverse-planning modes calculate the missing boundary. You can then apply it to the ordinary shift-length view for a final review.
This is a single-shift time calculation—not a full employee rota, a determination of rest entitlement, or a check for staffing coverage.
Understand shift length before and after breaks
The elapsed duration between clock-in and clock-out does not change simply because a break occurs inside the interval. A nine-hour shift remains a nine-hour scheduled span, whether it includes a paid rest break, an unpaid meal break, or both.
However, break classification changes how many of those hours are counted as credited time. If the nine-hour shift includes thirty unpaid minutes and fifteen paid minutes, credited time is eight hours and thirty minutes. Time excluding all recorded breaks is eight hours and fifteen minutes.
The calculator distinguishes all three figures: elapsed shift duration, credited duration after unpaid deductions, and time excluding both paid and unpaid break minutes.
You can add separately named break durations under Advanced Options. The total of all paid and unpaid breaks cannot exceed the elapsed shift length. Whether a break is legally paid is not established by this tool.
Measure 12-hour, 24-hour and longer shift intervals
Some organizations schedule shifts that last twelve hours or more. Twenty-four-hour duty windows are also used in certain services and operations. These are simply longer date-and-time intervals from the calculator's perspective.
A duty interval beginning Monday at 8:00 AM and finishing Tuesday at 8:00 AM lasts twenty-four wall-clock hours, assuming no intervening clock change.
Using the actual calendar end date is essential. The same start and finish clock times on the same date indicate zero duration, not a full day.
The tool accepts single intervals up to seventy-two hours, which accommodates extended duty calculations without attempting to build a multi-person schedule.
A long scheduled duty interval should not automatically be interpreted as continuous payable work. Sleep periods, standby arrangements, rest requirements and related rules may need separate analysis.
Convert shift durations into decimal hours correctly
Decimal-hour notation expresses minutes as a fraction of sixty. For example, thirty minutes equals 0.50 hours, fifteen minutes equals 0.25 hours, and forty-five minutes equals 0.75 hours.
A shift with seven credited hours and forty-five minutes equals 7.75 decimal hours—not 7.45 hours. The latter incorrectly treats minutes as hundredths of an hour.
This calculator stores shift and break calculations in integer minutes, then divides the appropriate result by sixty to produce decimal hours.
Two, three or four decimal places may be selected for display. This does not alter the underlying number of minutes.
Review the calculated shift before relying on it
Confirm that each calendar date is correct and that the finish boundary occurs after the start. For night shifts, verify the following-day date rather than assuming that a smaller end-time reading means the next day.
Review the total break minutes and how they were classified. Breaks cannot occupy more time than the shift itself, and negative break durations are invalid.
When using actual elapsed mode, confirm the time zone and any earlier-or-later repeated-hour selection. The calculator detects missing and ambiguous local clock times, but cannot independently verify which clock reading actually occurred.
Exports include the chosen time-calculation basis and recorded assumptions. Calendar events should also be reviewed in the receiving calendar application, especially when a floating local time is used.
A mathematically correct shift length does not establish employee attendance, a legal break policy, overtime eligibility, remuneration, shift safety or minimum rest compliance.
Common shifts and their calculated lengths
These examples distinguish the complete elapsed interval from hours remaining after unpaid breaks.
09:00–17:30
30-minute unpaid lunch
8h 30m 8h credited07:00–19:00
30-minute unpaid break
12h 00m 11h 30m credited22:00–06:00
Next day · 30-minute unpaid break
8h 00m 7h 30m credited08:00–08:00
Finish on the following date
24h 00m Before break deductionsFrequently asked questions
How do I calculate the length of a shift?
Subtract the starting date and time from the finishing date and time. The result is the elapsed shift duration. Unpaid breaks can then be deducted separately to estimate credited hours.
How long is a shift from 9 AM to 5 PM?
The complete interval lasts eight hours. With a thirty-minute unpaid break, the credited working duration is seven hours and thirty minutes.
How long is a shift from 7 AM to 7 PM?
It is a twelve-hour elapsed shift. With a thirty-minute unpaid break, credited time is eleven hours and thirty minutes.
How do I calculate a night shift?
Enter the actual beginning and finishing dates. A shift starting at 10 PM and ending at 6 AM the next day spans eight wall-clock hours before breaks.
Can I calculate the duration of a 24-hour shift?
Yes. Enter the starting date and time and the same clock time on the following date. The elapsed wall-clock duration is twenty-four hours unless a clock change affects actual elapsed time.
Are unpaid breaks part of the total shift length?
Unpaid breaks remain inside the start-to-finish elapsed interval. They are deducted only when calculating credited working hours.
Can I add more than one break?
Yes. The advanced panel supports separately named paid and unpaid break durations in addition to the main break inputs.
How can I find my clock-out time?
Open Advanced Options, select Find clock-out, enter the start time, required credited hours and unpaid breaks, then calculate the projected finish.
Can I calculate my required clock-in time?
Yes. Select Find clock-in and enter the required finishing time, credited duration and unpaid break minutes. The calculator works backward to determine the start.
Does the calculator adjust for daylight-saving changes?
Yes, in optional Actual elapsed mode with a valid IANA time zone. Standard wall-clock mode simply compares the entered local date and clock readings.
What happens if the clock repeats an hour?
In actual elapsed mode, select the earlier or later occurrence of that local clock time. This determines which real instant the calculator uses.
What is the difference between shift length and work hours?
Shift length focuses on one start-to-finish interval. A work hours total may subtract unpaid breaks and combine multiple separate work periods. ScheduleFlowLab provides distinct calculators for those tasks.
How are decimal shift hours calculated?
Divide the relevant duration in minutes by sixty. For example, seven hours and forty-five minutes equals 7.75 decimal hours.
Can I export the shift to my calendar?
Yes. Use the ICS export. Actual elapsed mode exports absolute UTC instants; wall-clock mode exports floating local date and time values.
Does this determine overtime pay?
No. It calculates the length of a single shift and break-adjusted hours. Overtime eligibility and pay depend on separate rules and information.
Are the shift calculations saved?
Entries and saved scenarios are stored in your browser where local storage is available. You can download a JSON backup for recovery.
Measure your next shift with confidence.
Enter the exact shift boundaries, review break-adjusted hours and keep a clear calculation for your records.
Open Shift Length Calculator ↑