Time Calculator

How to Use the Time Calculator

1. 1. Pick what you want to work out. Add or subtract times combines two durations, Time between two clock times measures a span, Add up a list totals a column of times, and Decimal hours converts in either direction.
2. 2. Type the times your way. Durations take h:mm or h:mm:ss (1:45:30) or units — 1h 45m 30s, 90 min, 1.5 h. In a list, a bare number counts as hours and a line that starts with a minus sign is subtracted.
3. 3. Add dates for long spans. Two clock times on their own are read as one day or one night: when the end is earlier than the start, the calculator assumes the span runs past midnight. Fill in both dates when it lasts longer than a day.
4. 4. Read the answer and the working. You get h:mm:ss, decimal hours, total minutes and total seconds, with each step of the arithmetic listed underneath and a running total for every line of a list.

How Time Arithmetic Works

Hours, minutes and seconds count in sixties, not tens, so adding times is column addition with a different carry: 60 seconds make a minute and 60 minutes make an hour. The calculator's first example, 1:45:30 + 2:30:45, works like this:

The widget takes the route a computer prefers: it turns each duration into seconds (1:45:30 = 6,330 s and 2:30:45 = 9,045 s), adds them to get 15,375 s, and divides back out — 15,375 = 4 × 3,600 + 16 × 60 + 15. Subtraction works the same way, borrowing 60 instead of 10. A duration is not a time of day, so the answer is never wrapped at 24 hours: 20:30 + 6:00 is 26:30:00, and a result below zero keeps its minus sign.

Converting Minutes to Decimal Hours

Payroll forms, invoices and timesheets usually want hours as a decimal. Divide the minutes by 60: 45 minutes is 45 ÷ 60 = 0.75 hours, so 7 hours 45 minutes is 7.75 hours — not 7.45, which is the most common timesheet error. To go the other way, multiply the decimal part by 60: 2.76 hours is 2 hours plus 0.76 × 60 = 45.6 minutes, which is 2:45:36.

That last point is why time billed in tenths of an hour moves in six-minute steps: 6 minutes is exactly 0.1 hours, while 10 minutes is 0.1666… and has to be rounded somewhere.

Time Between Two Clock Times: Overnight and Across Dates

With no dates, the calculator reads the two times as a single shift. When the end is later than the start it simply subtracts: 09:15 to 17:45 is 8:30. When the end is earlier — the calculator's example, 22:30 to 06:15 — the span must run past midnight, so 24 hours are added to the end first: (06:15 + 24:00) − 22:30 = 7:45.

For anything longer than a day, fill in both dates. The calculator counts the whole days between them and adds the clock difference: from 22:30 on 7 March to 06:15 on 9 March is 2 × 24:00 + (06:15 − 22:30) = 48:00 − 16:15 = 31:45. It treats every day as exactly 24 hours, which is what a timesheet wants. If the span crosses a daylight-saving change, the wall clock will disagree by an hour; use the Time Zone Converter when a zone's offset matters.

Common Mistakes

• Reading 7:45 as 7.45 hours. It is 7.75. Convert before multiplying by an hourly rate — at $20 an hour, the slip costs $6 on a single shift.
• Adding times like decimals. 1:50 + 1:20 is 3:10, not 2:70 or 2.70. Minutes over 59 always carry into the hours column.
• Forgetting the midnight wrap. 23:00 to 01:00 is 2 hours, not −22. The calculator wraps automatically when you leave the dates blank.
• Mixing 12- and 24-hour times. 09:00 to 05:00 is read as a 20-hour overnight span. Enter 17:00, or choose PM in the time picker.

Frequently Asked Questions

How do I calculate the hours between two times?

Subtract the start time from the end time. If the end is earlier than the start, the span crosses midnight, so add 24 hours to the end time first: 22:00 to 06:00 is (06:00 + 24:00) − 22:00 = 8 hours. Time between two clock times does the subtraction, the midnight wrap and the conversion to decimal hours for you.

How many hours is 9 to 5?

Eight hours: 09:00 to 17:00 is 17 − 9 = 8. An unpaid hour for lunch leaves 7 paid hours. Enter the end as 17:00 or 5:00 PM — a bare 5:00 means five in the morning, and the calculator would read the span as 20 hours overnight.

How do I convert hours and minutes to decimal hours?

Divide the minutes by 60 and add them to the hours: 7 hours 45 minutes is 7 + 45 ÷ 60 = 7.75 hours. Seconds are divided by 3,600. The Decimal hours mode converts in either direction and shows the arithmetic.

What is 0.1 hours in minutes?

Six minutes, because 0.1 × 60 = 6. Time billed in tenths of an hour is recorded in six-minute steps for that reason. Likewise 0.25 hours is 15 minutes, 0.5 is 30 and 0.75 is 45.

How do I add up hours worked in a week?

Choose Add up a list and put each day on its own line — as h:mm (7:45), with units (7h 45m) or as decimal hours (7.75). The calculator totals them, shows a running total beside every line and gives the week as h:mm:ss and as decimal hours, ready for a payroll form.

Can the result be more than 24 hours?

Yes. A duration is not a time of day, so the calculator never wraps it at 24: 20:30 + 6:00 is 26:30:00, and the result panel also shows it as 1 day + 2:30:00. Only Time between two clock times without dates assumes the span is shorter than a day.