Time Duration Calculator
Add two durations, subtract one from another, or paste a list and get the total. Results appear as h:mm:ss, decimal hours, minutes and seconds, ready for a timesheet.
Runs in your browser. Your files are never uploaded.
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How to use Time Duration Calculator
- Choose Add / subtract, Sum a list or Decimal hours.
- Type durations as h:mm:ss, h:mm or text like 1h 30m.
- Read the total as h:mm:ss, decimal hours, minutes and seconds.
- Copy the figure you need into your timesheet or invoice.
How durations are added
Each duration is converted to seconds: hours × 3600 + minutes × 60 + seconds. The seconds are added or subtracted, then converted back to hours, minutes and seconds. Working in whole seconds avoids the common mistake of adding minutes as if they were decimals.
Worked example: 2:45:30 plus 1:20:45 is 9,930 + 4,845 = 14,775 seconds, which is 4:06:15. A list of daily shifts 8:30, 7:45, 8:15 and 6:50 adds up to 31:20, which is 31.3333 decimal hours. A decimal value such as 7.75 hours converts to 7:45:00.
Useful for
- Timesheets and weekly hour totals for payroll or freelance invoices.
- Adding track lengths to plan a playlist or album running time.
- Totalling workout, study or project sessions.
- Subtracting break time from a work period.
- Converting between h:mm and decimal hours required by billing systems.
Input rules and limits
Minutes and seconds must be between 0 and 59 when you use the colon format. A single number without a colon is treated as minutes, so 90 means 1:30:00. Text forms such as 1h 30m and 45m are also understood. Decimal inputs in the text form are allowed, but the result is rounded to the nearest second. Lines that cannot be read are skipped and listed so you can correct them. Employers may round time in specific ways under their own policies, which this tool does not apply. Nothing is stored or sent anywhere. For payroll, double-check how your employer rounds minutes, because a few minutes per shift can add up to a noticeable difference over a month.
Why use this time duration calculator tool
- Flexible input. Accepts 2:45:30, 2:45, 90 (minutes) and 1h 30m 15s.
- Sum a list. Paste one duration per line and get the grand total; unreadable lines are flagged.
- Decimal hours. Convert both ways between 7:45 and 7.75 for payroll and billing.
- Whole-second maths. Calculations use integer seconds, so there is no rounding drift.
Frequently asked questions
How do I convert minutes to decimal hours?
Divide the minutes by 60. Forty-five minutes is 45 ÷ 60 = 0.75 hours, so 7 hours 45 minutes is 7.75 hours. In the other direction, multiply the decimal part by 60: 0.25 hours is 15 minutes.
Can the result be negative?
Yes. If you subtract a longer duration from a shorter one, the result is shown with a minus sign, which is useful for seeing how far under or over a target you are.
Does it work across midnight or with clock times?
This tool works with lengths of time, not clock times, so it does not wrap at 24 hours. Totals can exceed 24 hours, for example 31:20:00 for a week of shifts. To find the gap between two dates, use a date difference tool.
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