Time Duration Calculator guide
Pick a start and an end, get the exact gap in days, hours, and minutes, plus decimal hours you can drop straight into a timesheet. Daylight saving time is handled for you.
How the calculator works
You get two date-and-time inputs. They open on today, 9:00 AM to 5:30 PM, a typical US workday, so the first answer you see is 8 hours 30 minutes. Change either field and the result updates instantly.
Under the hood, both values are turned into exact moments in your device's local time zone, then subtracted. The result is shown three ways: a days, hours, and minutes breakdown for reading, total hours as a decimal for timesheets and invoices, and total minutes for anything billed by the minute.
If the end is earlier than the start, the calculator says so instead of printing a negative number, and still shows the absolute difference. That catches the most common data-entry slip: AM and PM swapped, or the end date left on today for a shift that ended tomorrow.
Decimal hours, explained
Payroll systems and client invoices want hours as a single decimal number, not hours and minutes. The conversion is minutes divided by 60. 30 minutes is 0.5 hours. 15 minutes is 0.25. 45 minutes is 0.75. 20 minutes is 0.333, usually rounded to 0.33.
The trap: 8 hours 30 minutes is 8.5, not 8.30. Writing 8.30 on a timesheet underpays you by 12 minutes, because 0.30 hours is 18 minutes. At $25 an hour, that is $5 lost on a single entry, and it compounds every week.
Many US employers round punches to the nearest quarter hour (the 7-minute rule: 1 to 7 minutes rounds down, 8 to 14 rounds up). This calculator shows the exact figure, so you can check that rounding evens out over time as the Department of Labor expects it to.
Worked example: a long weekend on call
Start Friday, September 25, 2026 at 9:00 AM. End Monday, September 28 at 5:30 PM. The calculator shows 3 days, 8 hours, 30 minutes. Total hours: 80.5. Total minutes: 4,830.
Check it by hand: three full days is 72 hours, and 9:00 AM to 5:30 PM on the fourth day adds 8.5. 72 + 8.5 = 80.5. At an on-call rate of $12 an hour, that span bills $966.
Overnight shifts and daylight saving time
Because every input carries a date, crossing midnight is not a special case. A shift from 10:00 PM Tuesday to 6:00 AM Wednesday is 8 hours. Just make sure the end date is the next day.
Daylight saving time is where naive calculators break. In most of the US, clocks jump from 2:00 AM to 3:00 AM on the second Sunday in March, and fall back from 2:00 AM to 1:00 AM on the first Sunday in November. A night-shift worker clocking 10:00 PM Saturday to 6:00 AM Sunday on the spring-forward weekend works 7 real hours, not 8. On the fall-back weekend the same shift is 9 hours.
This calculator uses your browser's time zone rules, so those shifts are already counted. The Fair Labor Standards Act pays for hours actually worked, so the 9-hour November shift is owed 9 hours of pay. Arizona (outside the Navajo Nation) and Hawaii do not observe DST, and there the numbers match the clock.
Mistakes that skew the total
Forgetting unpaid breaks. The calculator measures the full span. Subtract a 30-minute lunch yourself: 8.5 hours becomes 8.0 paid hours.
Mixing time zones. If a flight leaves New York at 8:00 AM Eastern and lands in Los Angeles at 11:15 AM Pacific, entering both clock times gives 3 hours 15 minutes, but the real flight is 6 hours 15 minutes. Convert both ends to your own zone first.
Adding decimals and minutes together. Once you convert to decimals, stay in decimals. 7.75 + 8.5 = 16.25 hours, which is 16 hours 15 minutes, not 16 hours 25.
Missing overtime. Under the Fair Labor Standards Act, non-exempt employees earn 1.5 times their regular rate for hours over 40 in a workweek. Add up each day's decimal total; five days of 8.5 hours is 42.5 hours, so 2.5 of them are overtime.
How we calculate: sources
Frequently asked questions
How do I calculate the hours between two times?
Subtract the start from the end. 9:00 AM to 5:30 PM is 8 hours 30 minutes. Enter both times here and the calculator shows the breakdown, total hours, and total minutes instantly.
How do I convert hours and minutes to decimal hours?
Divide the minutes by 60 and add them to the hours. 8 hours 30 minutes is 8 + 30/60 = 8.5 hours. 7 hours 45 minutes is 7.75 hours. 20 minutes is 0.33 hours.
Can it calculate across midnight or multiple days?
Yes. Each input has a date and a time, so an overnight shift from 10:00 PM to 6:00 AM the next day correctly shows 8 hours, and multi-day spans show days, hours, and minutes.
What happens if the end time is before the start time?
The calculator tells you the end is before the start and still shows the absolute difference, so a swapped entry does not leave you with a blank result.
Does it account for daylight saving time?
Yes. It uses your device's local time zone. A span that crosses the spring-forward night in March is 1 hour shorter than the clock suggests, and one that crosses the fall-back night in November is 1 hour longer.
Should I subtract my lunch break?
The calculator measures the whole span. For an unpaid 30-minute lunch on a 9:00 AM to 5:30 PM day, subtract 0.5 from the 8.5 total hours to get 8.0 paid hours.
Is my data private?
Everything runs in your browser. Nothing you enter is uploaded to a server or stored by us.
How many hours is 9 AM to 5 PM?
8 hours. With a 30-minute unpaid lunch, that is 7.5 paid hours, or 37.5 hours over a 5-day week.
How do I convert decimal hours back to minutes?
Multiply the decimal part by 60. 7.8 hours is 7 hours plus 0.8 x 60 = 48 minutes, so 7 hours 48 minutes.