Calculating working hours may seem straightforward, but breaks, different start and finish times, and overnight shifts can make it surprisingly easy to get the total wrong.
Whether you're checking your own hours, preparing a timesheet, tracking employee time or estimating labour costs, knowing how to calculate hours worked accurately can help prevent mistakes.
In this guide, we'll explain how to calculate working hours step by step, show practical examples, and cover some of the common situations that can make time calculations more complicated.
What Are Working Hours?
Working hours are the amount of time you spend carrying out work during a particular day, shift or week.
They are usually calculated from your start time to your finish time, with unpaid breaks deducted where applicable.
For example, if you start work at 9:00 AM and finish at 5:30 PM, the total time between those two points is 8 hours 30 minutes. If you take a 30-minute unpaid lunch break, your actual working time is:
8 hours 30 minutes − 30 minutes = 8 hours
Keeping an accurate record of working hours can be useful for timesheets, payroll, invoicing, project costing and checking how much time has been spent on a particular job.
How to Calculate Working Hours: A Simple Step-by-Step Guide
By ToolNestPro | Updated September 2026
How to Calculate Working Hours
To calculate working hours, subtract your start time from your finish time, then deduct any unpaid breaks.
The basic calculation is:
Working Hours = Finish Time − Start Time − Unpaid Breaks
Follow these three steps:
Step 1: Record your start and finish time
Write down the exact time you started and finished work.
Step 2: Calculate the total time between them
Subtract the start time from the finish time to find the total duration of the shift.
Step 3: Subtract unpaid breaks
If you took an unpaid lunch or other unpaid break, deduct that time from the total.
Example:
Start time: 8:30 AM
Finish time: 5:00 PM
Total time: 8 hours 30 minutes
Unpaid break: 45 minutes
Working time = 7 hours 45 minutes
How to Calculate Working Hours Across Midnight
Working hours can be slightly more difficult to calculate when a shift starts on one day and finishes the next.
For example, suppose you start work at 10:00 PM and finish at 6:00 AM the following morning.
From 10:00 PM to midnight = 2 hours
From midnight to 6:00 AM = 6 hours
Total time worked = 8 hours
If you took a 30-minute unpaid break, subtract it from the total:
8 hours − 30 minutes = 7 hours 30 minutes
Breaking an overnight shift into the time before and after midnight makes the calculation easier and helps avoid accidentally treating the finish time as earlier than the start time.
How to Calculate Weekly Working Hours
To calculate your total working hours for a week, work out the hours for each day and then add the daily totals together.
For example:
Monday: 8 hours
Tuesday: 7 hours 30 minutes
Wednesday: 8 hours
Thursday: 7 hours 30 minutes
Friday: 8 hours
Total weekly working hours = 39 hours
If your start and finish times vary from day to day, calculate each day's working time separately before adding the totals together.
This can be particularly useful when completing timesheets, checking payroll, tracking freelance or contractor hours, or monitoring the time spent on a project.
Common Working Hours Calculation Mistakes
Even simple time calculations can produce the wrong total if some details are overlooked. Common mistakes include:
1. Forgetting to subtract unpaid breaks
Calculating the entire time between starting and finishing can overstate the number of hours actually worked.
2. Mixing hours and minutes incorrectly
Time does not work in units of 100. For example, 7 hours 30 minutes is 7.5 hours, not 7.30 hours.
3. Getting overnight shifts wrong
When a shift crosses midnight, remember that the finish time falls on the following day.
4. Rounding too early
Rounding each shift before calculating a weekly total can make the final figure less accurate. Calculate the actual time first and round only when necessary.
5. Not recording start and finish times consistently
Keeping accurate records makes it much easier to check working hours later, especially when hours vary from day to day.
Calculate Your Working Hours
Want to skip the manual calculation? Use the free ToolNestPro Hours Calculator to enter your start time, finish time and break duration and calculate your working hours quickly.
Frequently Asked Questio
Do unpaid breaks count as working hours?
Usually, an unpaid break is deducted when calculating total working time. Whether a particular break is paid or unpaid depends on the employment arrangement, so check the terms that apply to you.
How do I convert minutes into decimal hours?
Divide the number of minutes by 60. For example, 30 minutes is 0.5 hours, 15 minutes is 0.25 hours, and 45 minutes is 0.75 hours.
How do I calculate hours if my working times change every day?
Calculate each day's hours separately using the start time, finish time and any unpaid breaks. Then add the daily totals together to find the total hours worked for the week or other period.