When you leave the dates blank and the end time is earlier than the start, the calculator adds one day — so 10:00 PM to 6:00 AM correctly returns 8 hours, not minus 16. Add dates and it measures the exact span between the two date-times, including any number of days.
Free Time Duration Calculator
Find the exact duration between two times. Enter a start and end time — add dates to span multiple days — and get the result in hours, minutes, seconds and decimal hours instantly.
What is a time duration calculator?
A time duration calculator works out how much time passes between a start time and an end time. Instead of counting on your fingers or doing the math in your head, you enter two times and it returns the exact gap — in hours and minutes, in seconds, and as decimal hours you can drop straight into a timesheet.
It handles the awkward cases automatically: shifts that run past midnight, breaks measured to the second, and spans that stretch across several days when you add dates. That makes it useful for everything from payroll and billing to cooking, studying and event timing.
How to calculate time duration
Get the duration between two times in three quick steps.
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Enter your start time and your end time.
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Spanning more than one day? Add a start and end date too — otherwise the calculator assumes the same day and rolls past midnight if the end is earlier.
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Read the duration in hours and minutes, plus total hours, minutes and seconds, then use Copy to grab the result.
How time duration is calculated
The duration is simply the end moment minus the start moment.
Duration = End time − Start time
Hours and decimal hours
Payroll and invoicing usually need decimal hours, not hours and minutes. 8 hours 30 minutes is 8.5 decimal hours (30 ÷ 60 = 0.5). The calculator shows both, so you never have to convert by hand.
What you can use it for
Work hours & payroll
Measure a shift from clock-in to clock-out, subtract breaks, and read the decimal hours for payroll.
Billing & projects
Time a task or client session and turn the span into billable hours and minutes.
Study & focus
Check how long a study block, workout or focus session actually lasted.
Cooking & events
Work out cooking, baking or event durations — including ones that run past midnight.
Stop calculating durations by hand
A calculator is great for a one-off. For ongoing work, WebWork tracks every start, stop and break automatically and turns the durations into timesheets and invoices.
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From a quick duration to tracked time
This calculator answers a single question. To capture durations all day, every day — across tasks, projects and people — WebWork Time Tracker records time automatically and turns it into reports, timesheets and payroll-ready hours. Explore more free tools and resources.
Try WebWork freeTurn Time Durations into Results with WebWork
A duration calculator gives you the number. WebWork captures every interval automatically and turns it into billable, reportable hours.
Automated Time Tracking
Track exact durations automatically instead of adding start and end times by hand.
Explore Time TrackingBillable Hours Tracker
Capture every billable minute and turn durations into client-ready totals.
Explore Billable HoursProject Budget Tracking
Roll task durations up into project budgets and monitor spend in real time.
Explore Project BudgetsTime Tracking & Invoicing
Convert tracked durations into accurate invoices in a few clicks.
Explore InvoicingFrequently asked questions
A time duration calculator is a tool that finds how much time passes between two times. You enter a start time and an end time and it returns the duration in hours and minutes, in seconds, and as decimal hours — without any manual math.
Subtract the start time from the end time. For example, 9:00 to 17:30 is 8 hours 30 minutes. If the end time is earlier than the start (an overnight shift), add 24 hours. The calculator above does this automatically.
Leave the date fields blank and, if the end time is earlier than the start, the calculator assumes the end is on the next day and adds 24 hours. So 22:00 to 06:00 returns 8 hours, not a negative number.
Yes. Add a start date and an end date and the calculator measures the exact span between the two date-times, including any number of whole days, then shows it as days, hours and minutes plus total hours.
Decimal hours express minutes as a fraction of an hour instead of as 60ths. 8 hours 30 minutes is 8.5 decimal hours, because 30 minutes is half an hour. Payroll and invoicing systems usually expect this format.
Divide the minutes by 60. So 15 minutes is 15 ÷ 60 = 0.25 hours, and 45 minutes is 0.75 hours. The calculator shows the decimal-hours total for you under Total hours.
Yes. If your time fields include seconds, the duration is calculated to the second and shown in the Total seconds result. If you only enter hours and minutes, the seconds are simply zero.
No practical limit. With dates added, you can measure a span of many days, weeks or months. Without dates, the calculator works within a single 24-hour cycle and rolls over midnight once.
Yes. The Total hours result is given in decimal hours, which is exactly what most payroll and invoicing tools expect. For ongoing tracking rather than one-off sums, WebWork records the durations automatically and builds the timesheet for you.
Yes. The WebWork time duration calculator is completely free, runs in your browser with no sign-up, and never sends your times anywhere.