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Time Calculator

Add, subtract, or calculate time duration

9:30 AM

Result

12h 00m

12:00 PM

Time Breakdown

Hours12
Minutes720
Seconds43,200

Example Calculations

1Add 2 Hours 30 Minutes to 9:30 AM

Inputs

Start Time9:30 (9:30 AM)
ModeAdd
Duration2 hours 30 minutes

Result

Result12h 0m (12:00 PM)

Start time = 9 x 60 + 30 = 570 minutes. Duration = 2 x 60 + 30 = 150 minutes. Total = 570 + 150 = 720 minutes. Result hours = floor(720 / 60) = 12, minutes = 720 mod 60 = 0. That is 12:00 PM.

2Time Between 9:00 AM and 5:30 PM

Inputs

Start Time9:00 (9:00 AM)
End Time17:30 (5:30 PM)
ModeBetween

Result

Duration8h 30m
Total Minutes510

Start = 9 x 60 + 0 = 540 minutes. End = 17 x 60 + 30 = 1050 minutes. Difference = abs(1050 - 540) = 510 minutes. Hours = floor(510 / 60) = 8, minutes = 510 mod 60 = 30. Duration is 8 hours and 30 minutes.

Frequently Asked Questions

Q

How do I calculate time duration between two times?

Subtract start time from end time. 9:00 AM to 5:30 PM = 8 hours 30 minutes. For overnight spans, add 24 hours. This calculator handles the math automatically, including multi-day spans.

  • Same day: End time - Start time
  • Overnight: Add 24 hours to end time, then subtract
  • Multi-day: Include full 24-hour periods
  • Example: 10:00 PM to 6:00 AM = 8 hours
  • Example: 9:00 AM to 5:30 PM = 8 hours 30 minutes
Start TimeEnd TimeDurationNotes
9:00 AM5:00 PM8 hoursStandard workday
9:00 AM5:30 PM8 hours 30 minWith 30 min extra
11:00 PM7:00 AM8 hoursOvernight shift
6:00 AM2:30 PM8 hours 30 minEarly shift
Q

How do I add or subtract time?

Add hours and minutes separately, then combine. 2:45 + 1:30 = 3 hours + 75 minutes = 4 hours 15 minutes. When minutes exceed 60, convert to hours. When subtracting, borrow an hour (60 min) if needed.

  • Add hours to hours, minutes to minutes
  • If minutes ≥ 60, subtract 60 and add 1 to hours
  • Example: 3:45 + 2:30 = 5:75 = 6:15
  • Subtraction: Borrow 60 min from hours if needed
  • Example: 5:15 - 2:45 = 4:75 - 2:45 = 2:30
Q

How do I calculate work hours for payroll?

Clock in to clock out time, minus unpaid breaks. 9:00 AM to 5:30 PM with 30 min lunch = 8 hours paid. Keep daily records and add weekly. Overtime typically starts after 40 hours/week or 8 hours/day.

  • Total hours = Clock out - Clock in - Unpaid breaks
  • Round to nearest quarter hour (company policy varies)
  • Track daily, sum for weekly total
  • Overtime: Usually 1.5× pay after 40 hrs/week
  • Keep detailed records for disputes
ScheduleGross HoursLunch BreakPaid Hours
9-5 Mon-Fri8 hrs/day30 min unpaid7.5 hrs/day
8-5 Mon-Fri9 hrs/day1 hr unpaid8 hrs/day
9-6 Mon-Fri9 hrs/day1 hr unpaid8 hrs/day
Q

How do I convert time to decimal hours?

Divide minutes by 60. 45 minutes = 45/60 = 0.75 hours. 7 hours 45 min = 7.75 hours. Useful for payroll, billing, and time tracking systems. Round to 2 decimal places.

  • Formula: Minutes ÷ 60 = Decimal
  • 15 min = 0.25, 30 min = 0.50, 45 min = 0.75
  • Payroll often uses decimal hours
  • Billing: Lawyers often bill in 6-min (0.1 hr) increments
TimeDecimal HoursCommon Use
15 minutes0.25 hoursQuarter hour
30 minutes0.50 hoursHalf hour
45 minutes0.75 hoursThree-quarter hour
7 hr 30 min7.50 hoursFull day minus lunch
8 hr 15 min8.25 hoursFull day plus 15 min
Q

What is the difference between 12-hour and 24-hour time?

12-hour uses AM/PM (1:00 AM to 12:59 PM, 1:00 PM to 12:59 AM). 24-hour uses 00:00-23:59 (military time). Convert PM to 24-hour: Add 12 to hours (3 PM = 15:00). Midnight = 00:00, Noon = 12:00.

  • AM: Midnight to 11:59 AM (00:00-11:59)
  • PM: Noon to 11:59 PM (12:00-23:59)
  • Convert to 24-hour: Add 12 to PM hours
  • 24-hour avoids AM/PM confusion
12-Hour24-HourNotes
12:00 AM00:00Midnight
6:00 AM06:00Morning
12:00 PM12:00Noon
3:00 PM15:00Afternoon (12+3)
9:00 PM21:00Evening (12+9)
11:59 PM23:59Before midnight
Q

How do I handle time zones?

Add or subtract hours based on zone difference. EST is 5 hours behind UTC (GMT). PST is 8 hours behind. 3 PM EST = 12 PM PST = 8 PM UTC. Consider daylight saving time shifts (1 hour difference).

  • UTC/GMT: Universal reference time
  • EST: UTC-5, PST: UTC-8, CST: UTC-6
  • Convert: Add hours going east, subtract going west
  • Daylight Saving: Most US clocks +1 hour Mar-Nov
  • Use world clock tools for accuracy

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Last Updated: Feb 12, 2026

This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.

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