Time Duration Calculator

How to add hours and minutes

Adding times by hand goes wrong in a predictable way: sixty minutes make an hour, not a hundred, so the carrying rules you use for ordinary numbers don't apply. This calculator does the carrying for you — every entry becomes minutes, the minutes are summed, and the total is converted back to hours and minutes.

1. Type one duration per row. Any common format works: 1:30, 1h 30m, 90, and 1.5h all mean the same ninety minutes.
2. Click Add row when you run out of fields, or press Enter in the last box. The × at the end of a row deletes it.
3. To subtract an entry — an unpaid break, a double-counted overlap, a target you're comparing against — click the + in front of the row so it flips to −.
4. Read the total under the list. It updates as you type and shows both h:mm (for timesheets) and decimal hours (for pay math).

Beside each row the calculator echoes what it understood — type 1.5h and the echo reads 1:30 — so a misread entry never slips silently into the total. Anything it can't parse gets a highlighted outline and stays out of the sum until you correct it.

How the math works

Every duration is converted to whole minutes before any arithmetic happens. 1:30 becomes 90 minutes, 8h 20m becomes 500, and a bare 475 is taken as 475 minutes. The signed entries are then summed — subtracted rows count negative — and the result is converted back the other way: divide by 60 to get the hours, and the remainder is the minutes. 2,330 minutes is 38 hours with 50 minutes left over, written 38:50.

Working in minutes avoids the classic mistake of adding h:mm values on an ordinary calculator. Punch in 2:45 + 1:50 as 2.45 + 1.50 and you get 3.95, which is wrong twice over: it isn't a time at all, and the real sum is 165 + 110 = 275 minutes, which is 4:35. Payroll systems work minutes-first for exactly this reason; if you ever need to do it on paper, the same routine is laid out in our guide to calculating time card hours by hand.

The decimal figure shown next to the total is the h:mm value divided out: 4:35 is 4 + 35⁄60 = 4.58 hours. Decimal hours are what you multiply by an hourly rate, so payroll software generally wants them; h:mm is what people read on a timesheet. If converting a single value between the two notations is all you need, the decimal hours converter handles either direction.

One format rule is worth memorizing: a bare whole number is read as minutes, while a number with a decimal point is read as hours. So 90 means 1:30 and 1.5 also means 1:30 — but 130 means 130 minutes, which is 2:10, not one hour thirty. When in doubt, use the colon.

Worked example: totaling a week of mixed-format durations

Say a week's hours arrive in five different shapes — a wall calendar, a text message, a sticky note, and an exported app log: Monday 8:15, Tuesday 7.5h, Wednesday 8h 20m, Thursday 475 (minutes, straight from the export), and Friday 6:50.

In minutes those are 495, 450, 500, 475, and 410. The sum is 2,330 minutes; 2,330 ÷ 60 = 38 remainder 50, so the week is 38:50, or 38.83 decimal hours.

Now suppose Wednesday's figure accidentally included a 1:30 personal appointment. Rather than re-deriving Wednesday, add a sixth row, enter 1:30, and flip it to −. The total drops by 90 minutes to 2,240 — that is 37:20, or 37.33 decimal hours. At $20.00 an hour, gross pay is 37.33 × $20.00 = $746.67. This week stays under 40 hours, so overtime never enters the picture; for weeks that do cross the line, the overtime pay calculator splits the hours and applies the multiplier.

Common weekly duration totals

The table below collects the weekly sums that come up constantly in payroll work: standard five-day patterns plus the usual compressed schedules. The per-shift lengths assume any unpaid break has already been taken out — if you're starting from clock-in and clock-out times, get each shift's length from the hours calculator first, or use the time card calculator to handle the whole grid at once.

Frequently asked questions