ISO 8601 Duration Calculator

This tool converts a length of time into an ISO 8601 duration string, the international standard format for representing durations in software and data. While most people write a duration as something like one and a half hours, computers need an unambiguous, language-independent format, and ISO 8601 provides it. A duration is written starting with the letter P, for period, followed by the number of days, then a T separating the date part from the time part, then hours, minutes and seconds, each tagged with a letter. So one hour and thirty minutes becomes PT1H30M, and one day, two hours and thirty minutes becomes P1DT2H30M. This format appears throughout modern systems: in APIs and web services, in databases, in scheduling and calendar data, in video and media metadata, and in programming languages that parse durations. This tool builds the string for you. You enter the days, hours, minutes and seconds, and the calculator assembles the correct ISO 8601 duration string, and also gives the total in seconds and minutes and a plain-language summary for reference. The results update as you type. Use it to produce a duration for an API request, to encode a time span in data, to learn the ISO 8601 format, or to check a duration you have been given. The standard is precise about the order and the letters: the T must appear before any hours, minutes or seconds, which is what distinguishes minutes, tagged M after the T, from months, also tagged M but before the T. Because this tool deals with days down to seconds, every M it produces is minutes, sitting after the T, so there is no ambiguity. The total seconds figure is handy when a system wants a raw count rather than the formatted string.

ISO 8601: P[days]DT[hours]H[minutes]M[seconds]S. The T separates date from time, so M after T is minutes. Total seconds is handy for raw counts.