Time Duration Calculator

Add, subtract, and convert time durations. Timesheet calculator, multi-duration sum, and time difference tool.

Enter durations in HH:MM:SS, HH:MM, or seconds. Use + or − operator per row.

Enter durations to calculate.

How to Use the Time Duration Calculator

  1. Duration Sum — enter multiple HH:MM:SS values and choose + or − for each row. Click "Add Row" for more entries. The total updates instantly.
  2. Time Difference — enter a start time and end time to find the elapsed duration. Enable "Overnight" for cross-midnight calculations.
  3. Convert — enter any duration and instantly see it in all units: days, hours, minutes, seconds, and decimal hours.
  4. Timesheet — enter start/end pairs for each work session and get the total hours worked for the day or week.

Accepted Time Formats

  • HH:MM:SS — hours, minutes, seconds (e.g., 1:30:45)
  • HH:MM — hours and minutes (e.g., 2:15)
  • SS — plain integer seconds (e.g., 90 = 1 minute 30 seconds)
  • 1.5h or 1.5 — decimal hours (e.g., 1.5h = 1 hour 30 minutes)

Timesheet Calculator

The timesheet mode is designed for freelancers, contractors, and employees who need to calculate total hours worked from clock-in / clock-out times. Enter one row per work session (e.g., morning: 09:00–12:30, afternoon: 13:30–18:00). The calculator adds all session durations and displays the total in hours and minutes. This is useful for weekly time tracking, invoicing by the hour, and payroll calculations.

Use Cases

Time duration calculations come up in many everyday scenarios. Video editors need to sum clip lengths to calculate total project runtime. Runners and athletes track split times and total workout duration. Project managers track time spent on tasks across multiple days. Music producers calculate total album length. Teachers plan class sessions with specific durations. This tool handles all of these — and unlike a spreadsheet, requires no formula knowledge.

Overnight Duration Calculation

When a shift or event crosses midnight — for example, a night shift from 22:00 to 06:00 — the end time is numerically earlier than the start time. This tool handles this correctly when you check the "Overnight" option in the Time Difference mode. It automatically adds 24 hours to the end time before calculating the difference, giving the correct 8-hour result.

Decimal Hours vs. HH:MM:SS

Time can be expressed as decimal hours (1.75h = 1 hour 45 minutes) or as HH:MM:SS. Both representations are common, but they arise in different contexts. Decimal hours are standard in payroll systems (1.5 hours × $20/hr = $30), while HH:MM:SS is used in video, audio, and sports timing. The Convert mode shows both representations and all other unit conversions simultaneously, making it easy to switch between them.

Frequently Asked Questions

HH:MM:SS, HH:MM, plain seconds, or decimal hours (e.g., 1.5h). Leading zeros are optional. For example: 1:30:00, 45:00, 90, or 1.5h all work.
Yes. The Duration Sum mode lets you add as many rows as needed. Click "Add Row" to insert more duration inputs with + or − operators.
Enter a start and end time for each work session. The calculator computes each session's duration and sums them into a daily or weekly total.
Yes. In the Time Difference mode, check "Overnight / cross-midnight" and the calculator adds 24 hours to the end time before computing the difference.
Results over 24 hours show as "D days HH:MM:SS". The breakdown also shows total hours, total minutes, total seconds, and decimal hours for easy conversion.