BYTETOOLS

Time Duration Calculator

Add or subtract hours, minutes and seconds, or sum a list of durations into a total shown in h:m:s and in total seconds. Free and 100% in-browser.

2:40:20
Total (h:m:s)
160.33
Total minutes
9,620
Total seconds
3
Durations summed

What is the Time Duration Calculator?

The ByteTools Time Duration Calculator works with lengths of time rather than clock times. Enter one duration and add or subtract another, or paste a whole list of durations to sum them up.

  • Sum any number of durations at once
  • Flexible input: h:m:s, m:s, or 1h 30m 20s style
  • Total shown as h:m:s and in total seconds and minutes
  • Handles very long totals beyond 24 hours
  • One-click copy of the total
  • Runs 100% locally — private time logs

How to use the Time Duration Calculator

  1. 1

    Enter one duration per line (e.g. 1:30:00, 45:20 or 90m).

  2. 2

    The tool sums every line into a running total.

  3. 3

    Read the total as h:m:s and as total minutes and seconds.

  4. 4

    Copy the total to paste into a sheet or invoice.

About the Time Duration Calculator

The ByteTools Time Duration Calculator works with lengths of time rather than clock times. Enter one duration and add or subtract another, or paste a whole list of durations to sum them up. The running total is shown both as clean h:m:s and as a raw number of seconds and minutes for copying into spreadsheets or scripts.

It is ideal for adding up video or podcast segment lengths, logging billable time, totalling workout intervals, or combining lap and cook times. Each line accepts flexible formats like 1:30:00, 90:00 or 45m 30s, so you can paste times straight from other tools without reformatting.

All arithmetic happens locally in your browser with JavaScript — no data is uploaded, so your time logs stay private and the tool works offline.

Frequently asked questions

How do I add up multiple time durations?

Put each duration on its own line — for example 12:30 and 8:45 — and the calculator converts every line to seconds, adds them, and shows the combined total in hours, minutes and seconds.

What time formats can I enter?

You can use colon formats like 1:30:00 (h:m:s) or 45:20 (m:s), or unit formats like 1h 30m 20s and 90m. Mixing formats across lines is fine; the tool normalises each line to seconds before adding.

Can the total go beyond 24 hours?

Yes. Durations are not clock times, so the total simply keeps counting — a sum of 30 hours displays as 30:00:00 rather than wrapping around a 24-hour clock.

How do I subtract one duration from another?

Prefix a line with a minus sign, for example -0:15:00, to subtract fifteen minutes from the running total. This lets you deduct breaks or corrections while still summing everything in one place.

What is the difference between a duration and a clock time?

A clock time is a point in the day, like 14:30, while a duration is a length, like 2 hours 30 minutes. This tool treats every value as a length, so 14:30 means fourteen and a half hours, not half past two.

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