How to use Time Duration Calculator
The time duration calculator adds up a list of times and gives you a single total. Write one duration per line in whatever format is natural — 1:30, 1h 30m, 90m, or a bare 0.5 meaning half an hour — and the tool parses them all, sums them, and reports the total in hours and minutes, in total minutes, and in decimal hours for timesheets. Lines it cannot read are skipped and listed rather than silently dropped. Everything runs in your browser with nothing uploaded.
- Enter one duration per line.
- Mix formats freely — 1:30, 1h 30m, 90m, or 0.5.
- Read the total in hours and minutes.
- Copy the decimal hours for a timesheet.
Your data never leaves your device — 100% private processing.
Why decimal hours matter
Time is stored in base 60, but money is stored in base 10, and that mismatch causes a surprising number of billing errors. Fifteen minutes is a quarter of an hour, so 5h 15m is 5.25 hours — not 5.15. Anyone who types 5.15 into an invoice has just undercharged. Because payroll and invoicing systems multiply an hourly rate by a decimal number of hours, converting correctly is essential. This calculator does the conversion for you, showing the same total three ways so you can read hours-and-minutes for a human and decimal hours for a spreadsheet. Copying the decimal figure straight across removes the most common source of timesheet arithmetic mistakes.
| Time | Minutes | Decimal hours |
|---|---|---|
| 5h 15m | 315 | 5.25 |
| 2h 30m | 150 | 2.50 |
| 0h 45m | 45 | 0.75 |
Mixing input formats
Real time logs are rarely consistent. One entry is a stopwatch reading of 1:30, the next is scribbled as “45m”, another as “2h 15m”, and a fourth is simply “0.5” because half an hour felt obvious at the time. Rather than forcing you to normalise everything by hand before adding, this tool understands all of those forms and converts each to minutes internally before summing. A bare number is interpreted as hours, since that is the most common shorthand. Anything genuinely ambiguous or malformed — a stray word, an impossible time like 1:75 — is skipped and reported back to you, so a single typo never silently corrupts the total.
Worked examples
Mixed formats
Inputs: 1:30, 45m, 2h 15m, 0.5
Result: 5h · 300 min · 5.00 h
Decimal
Inputs: 1:30
Result: 1.5 decimal hours
Bad line
Inputs: 1:30 and "nope"
Result: 1h 30m · 1 line skipped
Glossary
- Duration
- A length of time, as opposed to a point in time.
- Decimal hours
- A duration written as a single base-10 number, e.g. 5.25 hours.
- Timesheet
- A record of hours worked, usually totalled in decimal hours.
- Base 60
- The sexagesimal system in which 60 minutes make an hour.
Related reading
Frequently Asked Questions
Why use Time Duration Calculator?
- Adds up durations written in several different formats
- Reports the total in hours-and-minutes, minutes, and decimal hours
- Skips and reports unreadable lines instead of failing
- Handles any number of entries, instantly and privately
Common use cases
- Total the hours on a weekly timesheet
- Add up billable time across several tasks
- Sum workout, study, or practice sessions
- Convert logged time into decimal hours for invoicing
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