Time Duration Calculator

Calculate the duration between two clock times or add and subtract hours, minutes, and seconds with the Time Duration Calculator. This tool is purpose-built for working with time-of-day values — the hours, minutes, and seconds that make up a day — as opposed to calendar dates. Whether you need to total up billable hours on a timesheet, figure out how long a shift lasted, plan travel time, or add up the durations of multiple meetings, this calculator handles the arithmetic instantly and accurately.

The calculator offers two primary modes. In "Duration Between" mode, you enter a start time and an end time, and the tool computes the exact elapsed duration. It correctly handles overnight spans that cross midnight — for example, a night shift from 10:00 PM to 6:30 AM is correctly calculated as 8 hours and 30 minutes. Simply enable the "Crosses midnight" option when the end time falls on the following day.

In "Add / Subtract" mode, you can combine multiple time durations arithmetically. This is ideal for totaling up meeting lengths, summing billable sessions, or computing net work time after subtracting breaks. For example, adding 1 hour 30 minutes plus 2 hours 45 minutes plus 50 minutes gives 5 hours and 5 minutes. The calculator handles minute and second overflow automatically, so you never need to manually carry values.

Results are displayed in multiple formats simultaneously: standard hours:minutes:seconds (e.g., 8:30:00), decimal hours (e.g., 8.50h), total minutes (e.g., 510), and total seconds (e.g., 30,600). The decimal hours format is particularly valuable for timesheet and billing systems, which typically require hours expressed as decimals rather than hours and minutes. Each format can be copied to your clipboard with a single click.

Common use cases are numerous and span both personal and professional contexts. Employees and freelancers use it to calculate daily work hours for timesheets. Shift workers use it to determine the length of their shifts, including overnight shifts. Fitness enthusiasts use it to total exercise durations across multiple sessions. Event planners use it to build agendas by adding session lengths. Students use it to track study time. Travelers use it to estimate journey durations. Cooks use it to add up recipe preparation times. The applications are virtually limitless.

It is important to distinguish this tool from the Date Difference Calculator. The Date Difference Calculator works with calendar dates (e.g., "March 1 to April 15") and counts days, weeks, and months. The Time Duration Calculator works with clock times (e.g., "9:15 AM to 5:30 PM") and counts hours, minutes, and seconds. For durations within a single day or spanning overnight, this is the right tool. For durations spanning multiple calendar dates, use the Date Difference Calculator.

All calculations run locally in your browser. No data is transmitted to any server, no account is required, and the tool is completely free with no usage limits. The interface is responsive and works on all screen sizes, from desktop monitors to mobile phones.