Single-shift time and pay tool
Shift Hours Calculator
Find the exact time from clock-in to clock-out, handle an overnight finish, subtract an unpaid break, apply optional rounding and estimate regular, extra and gross pay.
Last Updated: July 24, 2026
Calculate One Work Shift
Enter 12-hour time with AM or PM, or use 24-hour time. The default example is an overnight shift.
A shift hours calculator finds the time between one clock-in and one clock-out. It is useful for a day shift, night shift, weekend shift, freelance session or any other single work period. Enter the start and finish, choose how midnight should be handled and subtract only the break that should not count as worked time.
This tool keeps four figures separate. Gross shift span is the complete clock interval. Unpaid break is the entered deduction. Exact worked time is gross span minus that break. Pay hours use either exact time or the optional rounded result. The separation makes it easier to spot an incorrect AM or PM marker, an accidental midnight assumption, a duplicate break deduction or a pay estimate based on the wrong hours.
How to Use the Shift Hours Calculator
- Enter the clock-in time. Use 12-hour time with AM or PM, or enter a 24-hour reading.
- Enter the clock-out time in the same format or another accepted format.
- Select the clock-out day. Automatic mode treats an earlier finish as occurring on the following day.
- Enter the total unpaid break in minutes. Enter zero when every break remains paid or no break occurred.
- Leave rounding off unless a record, contract or payroll policy requires a specific increment and method.
- Select whether exact or rounded time should feed the pay preview. The exact result stays visible either way.
- Enter an optional hourly rate, extra-hours threshold, multiplier and fixed shift allowance.
- Select “Calculate Shift,” then review the clock span, break, exact work, pay hours and component tables.
Review the breakdown before copying the result. An end time earlier than the start often means an overnight shift, but it may also indicate a reversed AM or PM entry. Same day only is useful when you want the calculator to block that situation instead of assuming midnight was crossed.
Shift Hours Formula
Each clock reading is converted to milliseconds after midnight. One day is added when the selected clock-out rule places the finish on the following day. The break is then converted from minutes and removed.
Clock seconds = (hour × 3,600) + (minute × 60) + second
Gross shift time = clock-out instant − clock-in instant
Exact worked time = gross shift time − unpaid break
Decimal hours = worked seconds ÷ 3,600
The fixed time relationships follow the NIST time-unit reference. One minute equals 60 seconds, one hour equals 3,600 seconds and a conventional day equals 24 hours or 86,400 seconds.
Worked Example: Overnight Shift with a Break
Assume a shift begins at 9:00 PM, finishes at 6:30 AM the next day and includes a 30-minute unpaid break. The regular rate is $20 per hour, extra hours begin after 8 hours and the entered multiplier is 1.5.
- 9:00 PM to midnight is 3 hours.
- Midnight to 6:30 AM is 6 hours 30 minutes.
- Gross shift span is 9 hours 30 minutes.
- Exact worked time is 9 hours 30 minutes minus 30 minutes, or 9 hours.
- Regular time is 8 hours. Extra time is 1 hour.
- Regular pay is 8 × $20, which equals $160.
- Extra-hours pay is 1 × $20 × 1.5, which equals $30.
- Estimated gross shift pay is $190 before deductions.
No rounding is used in this example. If the same exact work time were rounded to an increment, the exact nine-hour result would remain visible and only the separate rounded value would change.
How Overnight Shift Calculation Works
A clock-out earlier than clock-in cannot be a positive same-day duration. Automatic mode therefore places the earlier finish on the next day. For example, 10:30 PM to 6:15 AM becomes 7 hours 45 minutes before a break. The setting does not add a day when the finish is later than the start.
- Automatic: an earlier clock-out means next day. Equal times mean zero.
- Same day only: an earlier finish produces an error. This helps catch a wrong AM or PM entry.
- Following day: the finish always moves one day forward. Equal times become exactly 24 hours.
Clock-only input cannot distinguish a 7-hour shift from a 31-hour interval when both have the same displayed start and finish. This page intentionally limits the model to one same-day or next-day shift. Use the Time Duration Calculator with explicit dates for a longer span.
Accepted 12-Hour and 24-Hour Times
The calculator accepts common clock notation. AM and PM are case-insensitive, and periods in a.m. or p.m. are allowed. Minutes and seconds are optional for whole-hour input. A time without AM or PM is treated as 24-hour time.
| Entry | Meaning | Equivalent |
|---|---|---|
| 8:30 AM | Morning time | 08:30 |
| 1 PM | One in the afternoon | 13:00 |
| 17:45 | 24-hour reading | 5:45 PM |
| 00:00 | Midnight | 12:00 AM |
| 12:00 | Noon | 12:00 PM |
| 21:15:30.5 | Time with fractional seconds | 9:15:30.5 PM |
Use a colon for clock time. The entry 8.30 is not accepted as 8 hours 30 minutes because a decimal point represents a different notation. In decimal-hour form, 8.30 hours equals 8 hours 18 minutes.
Break Deduction and Paid Breaks
The break field removes time from the gross shift span. Enter the combined excluded break in minutes. The calculator rejects a break longer than the shift and allows a break equal to the full span, which produces zero worked time.
Do not assume every break is unpaid. Rules depend on location, industry, contract, duties and break length. Under the U.S. federal framework, short rest periods are generally counted as work, while a bona fide meal period usually requires the worker to be completely relieved from duty. Review the current rule before removing time. The relevant U.S. provisions include 29 CFR 785.18 for rest periods and 29 CFR 785.19 for meal periods.
Exact Hours, Decimal Hours and Rounded Hours
Exact worked time uses hours, minutes and seconds. Decimal hours express the same duration in base 10. Divide the minute portion by 60. Seven hours 45 minutes equals 7.75 hours because 45 divided by 60 equals 0.75.
| Clock duration | Decimal hours | Calculation |
|---|---|---|
| 15 minutes | 0.25 | 15 ÷ 60 |
| 30 minutes | 0.50 | 30 ÷ 60 |
| 45 minutes | 0.75 | 45 ÷ 60 |
| 7 hours 45 minutes | 7.75 | 7 + (45 ÷ 60) |
| 8 hours 18 minutes | 8.30 | 8 + (18 ÷ 60) |
Optional rounding applies after the break. Nearest moves the result to the closest increment, down moves it to the lower increment and up moves it to the higher increment. For example, 7 hours 53 minutes rounded to the nearest 15 minutes becomes 8 hours. Rounded down, it becomes 7 hours 45 minutes. Rounded up, it becomes 8 hours.
A rounding option performs arithmetic. It does not establish a lawful payroll practice. U.S. federal regulation at 29 CFR 785.48 describes accepted time-clock rounding only when the practice does not, over time, underpay employees for work performed. Other jurisdictions or current employer systems may require exact time or another method.
How the Shift Pay Estimate Works
The pay section is optional. Currency changes the symbol and formatting only. It does not convert exchange rates. Enter the gross regular rate for one hour, an extra-hours threshold, the applicable multiplier and any fixed shift allowance.
Regular hours = lower of pay hours or entered threshold
Extra hours = pay hours − regular hours
Regular pay = regular hours × hourly rate
Extra-hours pay = extra hours × hourly rate × multiplier
Estimated gross pay = regular pay + extra-hours pay + fixed allowance
This is a single-shift scenario. A daily threshold in this form does not replace weekly overtime, consecutive-day rules, double time, minimum call-out pay, split-shift premiums or a legal regular-rate calculation. Use the Overtime Pay Calculator for weekly or daily-plus-weekly modeling.
Common Shift Calculation Errors
Reversing AM and PM
12:00 AM is midnight. 12:00 PM is noon. A reversed marker can change the result by 12 hours. Use same-day mode to block an earlier finish when the shift should not cross midnight.
Forgetting an overnight finish
Subtracting 21:00 from 06:30 produces a negative clock difference. An overnight calculation needs the following-day rule, which adds one 24-hour day before subtracting the start.
Entering a paid break as unpaid
The calculator removes the full break entered. Confirm whether the break is excluded under the relevant record, policy and law before deducting it.
Treating minutes as hundredths
Eight hours 30 minutes equals 8.5 decimal hours, not 8.30. Convert minutes by dividing by 60.
Using a daily threshold as a legal conclusion
The entered threshold is a pay scenario. Eligibility, covered hours, regular-rate components and applicable weekly or daily rules require a separate check.
Using wall-clock math across a time change
This tool uses fixed 24-hour wall-clock arithmetic. It does not identify a time zone or daylight-saving transition. A displayed 1:00 AM to 4:00 AM span may represent a different real duration on a clock-change date.
Which Work-Hours Tool Should You Use?
| Question | Best tool | Main input |
|---|---|---|
| How long was one shift after a break? | Shift Hours Calculator | One clock-in and clock-out |
| What is the total from several independent intervals? | Hours Calculator | Multiple start and end rows |
| How much time passed across known dates? | Time Duration Calculator | Dates and clock readings |
| How should weekly or daily overtime be estimated? | Overtime Pay Calculator | Hours, coverage and pay rules |
| What annual salary matches an hourly rate? | Hourly to Salary Calculator | Rate and work schedule |
Accuracy and Limitations
The result is only as accurate as the entered times and assumptions. Review the source record, AM or PM markers, clock-out day, break, rounding basis, rate, threshold and multiplier. Keep the original time record when the calculation supports payroll, billing, attendance, compliance or a contract.
The calculator does not infer a country, state, occupation, collective agreement, exemption, minimum wage, tax, deduction, benefit, paid-break rule, time zone or daylight-saving change. Estimated gross pay is before tax and other deductions. It is not a payslip, entitlement decision or legal opinion.
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Frequently Asked Questions
How do I calculate the hours in one work shift?
Subtract clock-in from clock-out, add one day when the shift crosses midnight, then subtract any unpaid break. The calculator also converts the result to decimal hours and total minutes.
Can the Shift Hours Calculator handle an overnight shift?
Yes. Automatic mode treats a clock-out earlier than clock-in as occurring on the following day. You may also force the same day or following day.
What happens when clock-in and clock-out are equal?
Automatic and same-day modes return zero gross time. Select Following day when equal clock readings represent a complete 24-hour shift.
How do I subtract a lunch or rest break?
Enter the combined unpaid break in minutes. The calculator removes it from the gross span and rejects a break longer than the shift.
Does the calculator accept both 12-hour and 24-hour time?
Yes. Enter a 12-hour time with AM or PM, or enter a 24-hour reading from 00:00 through 23:59. Seconds are optional.
How are decimal shift hours calculated?
The selected worked duration in seconds is divided by 3,600. For example, 7 hours 45 minutes equals 7.75 decimal hours.
Does rounding change the exact worked time?
No. Rounding creates a separate result after the break. Exact worked time remains visible, and you choose whether exact or rounded hours feed the pay estimate.
Does the pay estimate determine overtime eligibility?
No. The threshold and multiplier are user-entered scenarios. Actual overtime eligibility and pay depend on the governing law, coverage, contract and employer policy.
Does the result account for time zones or daylight saving time?
No. The calculator uses fixed 24-hour wall-clock arithmetic. Use exact dates and a location-aware method when a shift crosses zones or a clock change.