Hours & Minutes Calculator

A bare number means minutes, so typing 8 gives you eight minutes

This is the first thing to know, because it is the mistake that produces a plausible wrong answer rather than an error. Measured: entering 8 and 0 gives 0h 8m, not eight hours.

If you mean hours, write them in one of the forms the parser recognises: 8:00, or 8h, or 8h 0m. A bare integer is always taken as a count of minutes, which is useful when you are adding up minute totals and dangerous when you are adding up shifts.

A decimal like 1.5h is silently read as 5 hours

This is the most serious thing on this page and nothing on screen warns you about it. The parser looks for a run of digits immediately before an h, and in 1.5h that run is 5. Measured: 1.5h gives 5h 0m.

So a timesheet entered as 7.5h would be read as seven and a half hours by a person and as 5 hours by this tool, with a green OK beside it. There is no error state, because nothing about the input is invalid as far as the parser is concerned.

Never enter decimal hours here. Write 1:30 or 1h 30m. If what you have is decimal hours, use the Decimal hours figure in the results as your output rather than your input, or multiply by 60 and enter the minutes as a bare number.

A related silent loss: 1h30, with no m after the thirty, is measured as 1h 0m. The parser needs the unit letter, so the thirty is simply not seen. Always write the m.

Minutes above 59 are accepted, not corrected

Measured: 1:75 is read as 135 minutes and reported as 2h 15m. The tool treats the part after the colon as a plain minute count and adds it, so seventy-five minutes becomes an hour and a quarter.

That is arguably the useful behaviour, since it lets you type 0:150 for two and a half hours, and it is certainly not an error. But if you mistype 1:75 for 1:15 you will get an answer that is an hour out and looks fine. A single-digit minute field also works: 1:5 is measured as 1h 5m, which is five minutes past, not fifty.

Negative times work throughout, which is what makes it useful for balances

Subtracting a bigger time from a smaller one gives a negative result rather than an error or a wrap-around. Measured:

• 1:00 minus 2:30 gives -1h 30m, with total minutes -90.
• -1:30 is parsed as negative ninety minutes, so the sign applies to the whole time rather than just the hours.

So you can use this for a flexitime balance or an over-and-under against a target, in either direction, and the Total minutes figure carries the sign.

Decimal hours are shown to four places, which is a conversion and not a rounding

Every result also appears as decimal hours to four decimal places. Measured: eight minutes is 0.1333 hours, and two and a quarter hours is 2.2500.

Four places is enough to be exact for every whole number of minutes except the ones that recur: a third of an hour is exactly 20 minutes but 0.3333 hours. If you are billing from this figure, bill from the minutes and convert once at the end, rather than adding up rounded decimal hours, because the rounding error compounds. Twenty minutes three times is exactly one hour; 0.3333 three times is 0.9999.

What this tool deliberately does not do

• No seconds. Hours and minutes only, in and out.
• No dates, and so no overnight shifts. It does arithmetic on durations, not on clock times, so it cannot work out that 22:00 to 06:00 is eight hours. For spans across days use Days Between Dates.
• No more than two values. One operation on two times, so a week of shifts has to be added two at a time, or converted to minutes and summed elsewhere.
• No rounding to a billing increment. Nothing rounds to the nearest 6, 15 or 30 minutes.
• No rate, so no money. It will not multiply hours by a pay rate.
• No validation of what you meant. As above, decimal hours and minute fields over 59 are accepted and converted, not questioned.

Nothing is uploaded. The arithmetic is a few lines of JavaScript running in your browser, and what you type never leaves your device.

Sources

• Why a run of digits before a letter is matched the way it is, which is the cause of the 1.5h result: regular expression character classes and quantifiers. developer.mozilla.org
• Durations as distinct from clock times, and the notation for each: ISO 8601 as profiled in RFC 3339. rfc-editor.org/rfc/rfc3339
• Fixed-place decimal formatting, which produces the four-place figure: toFixed. developer.mozilla.org

Every behaviour and every result on this page was measured against this tool as it is published, in a browser, on 14 October 2026. Where the page says what the tool does not do, that is a statement about this tool, not about time arithmetic in general.