Seconds to HH:MM:SS Converter

Have a raw duration in seconds and need it as HH:MM:SS — or the reverse? Type seconds and get the clock format, days, a plain-English breakdown, and the ISO 8601 duration instantly; or type a HH:MM:SS string to get the total seconds back. Everything updates as you type and runs locally.

How to use the Seconds to HH:MM:SS Converter

Type a value in either field and the other follows. Enter a count in Total seconds — whole or decimal — and the HH:MM:SS box shows the equivalent clock-style duration; the cards below add the day count, a human-readable breakdown like "1 hour, 2 minutes, 5 seconds", and the ISO 8601 duration string. Type a duration into the HH:MM:SS box instead and the total seconds are computed back for you.

The HH:MM:SS field is flexible about input. You can write 1:02:05 or 01:02:05 for hours:minutes:seconds, or just 2:05 for minutes:seconds, or a bare number for seconds. Fractional seconds such as 1:30.5 are kept. The hours field is not capped at 24, so a long duration like 50:00:00 (fifty hours) is valid and will not roll over into days unless you read the day card.

It all runs in your browser and updates instantly, so it works offline and nothing you type is sent anywhere.

Seconds, clock time, and ISO 8601 durations

A duration and a clock time look the same but mean different things. HH:MM:SS as a duration is just a count of elapsed time written in base-60 groups: 3,725 seconds is one hour, two minutes, and five seconds, written 01:02:05. The same string can also name a time of day — 1:02:05 in the morning — but as a duration it has no starting point and the hours can exceed 24. This tool always treats the value as a duration, which is why it never wraps at 24 hours and offers a separate day count for convenience.

Converting is plain arithmetic with the fixed factors 60 seconds per minute, 60 minutes per hour, and 24 hours per day. To go from seconds you take successive remainders: hours are the total divided by 3,600, the leftover divided by 60 gives minutes, and what remains is seconds. To go the other way you multiply each field by its factor and add. The only subtlety is fractional seconds and rounding — a value like 90.5 seconds is 1 minute 30.5 seconds, and the tool preserves the fraction rather than silently truncating it, because dropping sub-second precision is a common source of drift when durations are summed repeatedly.

The ISO 8601 duration is the standardized, locale-independent way to write the same span. It starts with the letter P (for "period") and uses T to separate the date part from the time part, so one hour two minutes five seconds is PT1H2M5S. Fields that are zero are omitted, and the format scales up to days, months, and years (P1Y2M10DT2H30M). It is what APIs, databases, and formats like JSON Schema and XML use to exchange durations unambiguously, since "01:02:05" alone does not say whether it is hours-minutes-seconds or something else. Knowing the ISO form is handy whenever you need to store a duration in a way another system will parse the same way you meant it.

Common use cases

  • Reading raw timestamps. Turn a duration logged in seconds into a readable HH:MM:SS figure.
  • Media and video. Convert a runtime in seconds to clock format, or a timecode back to seconds for seeking.
  • API and config values. Translate between seconds (common in code) and the ISO 8601 duration many APIs expect.
  • Quick math. Find how many hours and minutes a large second count represents without a calculator.

Frequently asked questions

What formats does the HH:MM:SS box accept?
You can enter H:M:S, M:S, or a bare number of seconds, with or without leading zeros. Fractional seconds like 1:30.5 are preserved. Anything unparseable shows a short error.

Do hours roll over into days?
No. The HH:MM:SS output treats the value as a pure duration, so hours can exceed 24 (for example 50:00:00). A separate card shows the equivalent number of days if you want it.

What is the PT…S string?
That is the ISO 8601 duration format, the standard way APIs and databases represent a span of time. PT1H2M5S means one hour, two minutes, five seconds.

Are fractional seconds supported?
Yes. Decimals in the seconds field are kept through the conversion rather than truncated, which avoids rounding drift when durations are added together.