Utility

Time Duration Calculator

Calculate the time between two moments, add or subtract durations, and convert hours:minutes to decimal time for timesheets and billing.

Quick Answer

Time duration is the elapsed time between two points, expressed in hours, minutes, and seconds. To convert hours and minutes to decimal time (for billing), divide the minutes by 60 — for example, 2 hours 30 minutes equals 2.5 decimal hours. One day has 1,440 minutes or 86,400 seconds.

08:30:00
Decimal Hours
8.5
Total Minutes
510
Total Seconds
30,600
$
/hour

About This Tool

The Time Duration Calculator is a free online tool designed to simplify everyday time arithmetic. Whether you are a freelancer tracking billable hours, a project manager estimating schedules, or someone who simply needs to know how long a task took, this calculator handles the math instantly. All calculations run in your browser — nothing is sent to a server.

The Time Between mode calculates the exact duration between a start and end time. It shows the result in hours:minutes:seconds as well as total minutes, total seconds, and decimal hours. If your work spans midnight or multiple days, toggle on the date inputs for an accurate multi-day calculation. The built-in billing section lets you enter an hourly rate and see the total billable amount immediately, saving you from opening a separate spreadsheet.

Add/Subtract Time takes a starting clock time and adds or subtracts a duration you specify. The result is shown in both 24-hour and 12-hour (AM/PM) format, with a note if the result crosses into the next or previous day. This is useful for planning meeting end times, estimating arrival times, or working out shift schedules.

Time to Decimal converts between hours:minutes notation and decimal hours. Payroll systems, invoicing software, and timesheet apps frequently require decimal format (e.g., 1 hour 45 minutes = 1.75 hours). The converter works in both directions and includes a quick-reference table of common quarter-hour increments. Freelancers billing by the hour will find this especially helpful when preparing invoices or logging time in tools that only accept decimal input.

Frequently Asked Questions

How do I calculate time between two clock times?
Enter a start time and end time in the "Time Between" tab. The calculator subtracts the start from the end to give you the duration in hours, minutes, and seconds. If the end time is earlier than the start, it assumes the end is on the next day. You can also enter specific dates for multi-day calculations.
What is decimal time and why is it used?
Decimal time expresses hours and minutes as a single decimal number. For example, 1 hour 30 minutes becomes 1.5 hours. Freelancers, consultants, and payroll systems use decimal time because it is easier to multiply by an hourly rate. Most invoicing and timesheet software expects decimal format.
How do I convert 3 hours 45 minutes to decimal?
Divide the minutes by 60 and add to the hours: 45 / 60 = 0.75, so 3:45 = 3.75 decimal hours. Our Time to Decimal tab does this conversion instantly, and also shows the reverse (decimal to hours:minutes).
Can I calculate billable hours with this tool?
Yes. In the Time Between tab, after calculating a duration, enter your hourly rate in the billing section. The tool multiplies the decimal hours by your rate to show the total billable amount. This is useful for freelancers tracking project time.
Does this tool work across midnight or multiple days?
Yes. If you only use time inputs (no dates), the calculator assumes the end time is on the same day or the next day if it is earlier than the start. For multi-day spans, use the optional date inputs to get an exact duration down to the second.

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