Time Calculator
Add, subtract, and calculate time differences with hours, minutes, and seconds.
Time Calculations
Time Addition
Time to Seconds
Seconds to Time
Quick Calculations
Understanding Time Calculations
Time calculations are essential in everyday life—from tracking work hours and planning schedules to timing events and calculating durations. Unlike decimal numbers, time uses a base-60 system (sexagesimal) for minutes and seconds, which requires special handling for arithmetic operations.
Our time calculator handles the complexity of carrying and borrowing across hours, minutes, and seconds, giving you accurate results instantly.
Add Time
Sum multiple time durations together with automatic carry-over from seconds to minutes to hours.
Subtract Time
Find the difference between time durations with proper borrowing across units.
Time Between
Calculate the exact duration between two clock times.
Convert Units
Easily convert between seconds, minutes, hours, days, and weeks.
How Time Arithmetic Works
Time arithmetic follows different rules than regular math because of the base-60 system:
The Base-60 System
There are 60 seconds in a minute and 60 minutes in an hour. When adding, if seconds exceed 59, carry 1 to minutes. If minutes exceed 59, carry 1 to hours. This is why 1:45:30 + 0:30:45 equals 2:16:15, not 1:75:75.
Adding Time
Add each unit separately (seconds, minutes, hours), then normalize: 75 seconds becomes 1 minute 15 seconds. 90 minutes becomes 1 hour 30 minutes. Always work from smallest unit to largest.
Subtracting Time
When subtracting, borrow from larger units if needed: To subtract 45 seconds from 30 seconds, borrow 1 minute (60 seconds), making it 90 - 45 = 45 seconds while reducing minutes by 1.
Converting to Seconds
For complex calculations, convert everything to seconds first: 2:30:45 = (2 × 3600) + (30 × 60) + 45 = 7200 + 1800 + 45 = 9045 seconds. Then convert back after calculations.
Common Time Calculation Scenarios
Here are practical situations where time calculations are essential:
Work Hours Tracking
Calculate total weekly hours by adding daily work times. If you worked 8:30, 7:45, 9:15, 8:00, and 6:30, your total is 40:00 hours. Many payroll systems require this for accurate compensation.
Exercise & Sports
Track workout durations or compare race times. A marathon runner who completed segments of 1:52:30 and 2:15:45 has a total time of 4:08:15.
Cooking & Recipes
Calculate total cooking time when a recipe has multiple steps: 15 minutes prep + 45 minutes baking + 10 minutes cooling = 1 hour 10 minutes total.
Travel Planning
Add flight times, layovers, and transfers. A trip with a 2:45 flight, 1:30 layover, and 3:15 connecting flight totals 7:30 of travel time.
Media Duration
Sum up video lengths for playlists or calculate remaining watch time. Useful for content creators planning video series or viewers managing watch time.
Event Planning
Calculate total event duration including setup, main event, and cleanup times to ensure proper venue booking and scheduling.
Time Unit Conversions
Understanding how time units relate to each other is fundamental for calculations:
| From | To | Multiply By | Example |
|---|---|---|---|
| Hours | Minutes | 60 | 2.5 hours = 150 minutes |
| Hours | Seconds | 3,600 | 1 hour = 3,600 seconds |
| Minutes | Seconds | 60 | 45 minutes = 2,700 seconds |
| Days | Hours | 24 | 3 days = 72 hours |
| Weeks | Days | 7 | 2 weeks = 14 days |
| Weeks | Hours | 168 | 1 week = 168 hours |
Decimal Time vs. Standard Time
Many business applications use decimal hours (e.g., 7.5 hours) rather than standard time (7:30). Here's how to convert:
Standard to Decimal
Divide the minutes by 60 and add to hours. For 2:45 → 45÷60 = 0.75, so 2:45 = 2.75 hours. For 3:20 → 20÷60 = 0.333, so 3:20 ≈ 3.33 hours.
Decimal to Standard
Multiply the decimal portion by 60 to get minutes. For 4.25 hours → 0.25×60 = 15 minutes, so 4.25 hours = 4:15. For 2.5 hours → 0.5×60 = 30 minutes = 2:30.
Common Conversions
Memorize these: 0.25h = 15min, 0.5h = 30min, 0.75h = 45min. For uncommon values: 0.1h = 6min, 0.2h = 12min, 0.33h ≈ 20min.
Payroll Use
Employers often round to nearest quarter hour: 7:07 becomes 7:00 (or 7.0h), 7:08 becomes 7:15 (7.25h). Know your company's rounding policy.
24-Hour vs. 12-Hour Time
The calculator works with both 24-hour (military) time and 12-hour (AM/PM) formats:
Morning Hours (AM)
12:00 AM (midnight) = 00:00, 1:00 AM = 01:00, through 11:59 AM = 11:59. The 12-hour and 24-hour formats are the same for 1-11 AM.
Afternoon/Evening (PM)
12:00 PM (noon) = 12:00, 1:00 PM = 13:00, 2:00 PM = 14:00, through 11:59 PM = 23:59. Add 12 to convert PM hours (except 12 PM).
International Use
24-hour time is standard in most countries, military, aviation, and healthcare. It eliminates AM/PM confusion and is clearer for scheduling across time zones.
Common Mistakes
12:30 AM is early morning (00:30), not afternoon. 12:30 PM is early afternoon (12:30). Midnight is 12:00 AM or 00:00, noon is 12:00 PM or 12:00.
Time Zones and Duration
When calculating time across time zones, consider these factors:
Duration Is Absolute
A 3-hour flight takes 3 hours regardless of time zones. However, the clock times at departure and arrival will differ. Flying east 'loses' time on the clock; flying west 'gains' time.
Converting Time Zones
To convert, add or subtract the UTC offset difference. EST (UTC-5) to PST (UTC-8): subtract 3 hours. 3:00 PM EST = 12:00 PM PST.
Daylight Saving Time
DST changes can affect duration calculations crossing the transition. Spring forward 'loses' an hour, fall back 'gains' an hour on those specific days.
International Date Line
Crossing the International Date Line changes the date. Flying west across it, you repeat a calendar day. Flying east, you skip a day.
Frequently Asked Questions
How do I add hours and minutes together?
Add hours to hours and minutes to minutes separately. If minutes exceed 60, subtract 60 from minutes and add 1 to hours. For example: 2:45 + 1:30 = 3:75 → 4:15 (75 min = 1 hr 15 min, so 3+1=4 hours and 15 minutes).
How do I convert 2 hours 30 minutes to decimal?
Divide the minutes by 60 and add to hours: 30 ÷ 60 = 0.5, so 2:30 = 2.5 hours. For 2:45, it's 45 ÷ 60 = 0.75, so 2:45 = 2.75 hours.
What's the difference between 12 AM and 12 PM?
12 AM is midnight (the start of a new day, 00:00 in 24-hour time). 12 PM is noon (middle of the day, 12:00 in 24-hour time). This is a common source of confusion.
How do I calculate time between two dates?
For times on the same day, subtract start from end. For different days, calculate the remaining time on day one, add full days in between, and add time elapsed on the final day. Our calculator handles this automatically.
How many hours are in a year?
A regular year has 365 days × 24 hours = 8,760 hours. A leap year has 366 × 24 = 8,784 hours. The average accounting year uses 8,766 hours (365.25 days × 24).
How do I track work hours for payroll?
Record start and end times for each work period. Subtract start from end to get daily hours (minus any unpaid breaks). Add all daily hours for weekly totals. Convert to decimal hours if required by your payroll system.
Why does time use base-60?
The base-60 system (sexagesimal) originated with ancient Babylonians around 2000 BCE. They chose 60 because it has many divisors (1,2,3,4,5,6,10,12,15,20,30,60), making fractions easier to work with before decimal notation existed.
Can I calculate negative time?
Time durations can't be negative, but when subtracting, a negative result means the second time is actually earlier than the first. Our calculator will show the absolute duration and indicate which time comes first.
Pro Tips
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