Time Calculator
Add, subtract, and convert time with support for both 12-hour and 24-hour formats, plus decimal hour conversion for payroll.
How to Use the Time Calculator
Perform time calculations quickly and accurately with support for both 12-hour and 24-hour time formats.
- Choose your time format: Toggle between 12-hour (AM/PM) and 24-hour format based on your preference.
- Select an operation: Add Time, Subtract Time, or calculate the Time Between two times.
- Enter time values: Fill in hours, minutes, and seconds. For 12-hour format, select AM or PM.
- View results: See the result time plus breakdowns in total hours, minutes, seconds, and decimal hours.
Time Calculation Formulas
Adding time:
Result (seconds) = Start Time (seconds) + Added Time (seconds)
Subtracting time:
Result (seconds) = Start Time (seconds) - Subtracted Time (seconds)
Time difference (between two times):
Difference = Time 2 (seconds) - Time 1 (seconds)
Converting to decimal hours:
Decimal Hours = Hours + (Minutes ÷ 60) + (Seconds ÷ 3600)
Converting 12-hour to 24-hour format:
24h Hour = 12h Hour + 12 (if PM and not 12 PM)
24h Hour = 0 (if 12 AM)
All time calculations internally convert to total seconds, perform the arithmetic, then convert back to hours, minutes, and seconds for display. For time-between calculations, if Time 2 is earlier in the day than Time 1, the calculator adds 24 hours to Time 2 to handle overnight spans.
What is Time Calculation?
Time calculation involves adding, subtracting, and comparing time values. Unlike regular arithmetic, time operates on a base-60 system (60 seconds per minute, 60 minutes per hour) rather than base-10. This makes manual time math error-prone, especially when carrying over minutes to hours or handling AM/PM conversions.
Common applications include payroll processing (calculating total work hours), project management (summing task durations), cooking and baking (adding prep and cook times), fitness tracking (totaling workout durations), and travel planning (calculating arrival times across time zones).
The decimal hours output is particularly important for payroll systems, which require time in decimal format rather than hours and minutes. For example, an employee who works 7 hours and 45 minutes should be recorded as 7.75 decimal hours for accurate wage calculation.
Understanding Decimal Hours
Decimal hours express time as a decimal number instead of hours and minutes. This format is commonly used for payroll, billing, and time tracking systems.
Examples:
- 1 hour 30 minutes = 1.5 decimal hours
- 2 hours 15 minutes = 2.25 decimal hours
- 45 minutes = 0.75 decimal hours
- 8 hours 45 minutes = 8.75 decimal hours
Conversion formula: Decimal hours = Hours + (Minutes ÷ 60) + (Seconds ÷ 3600)
For example, 2 hours 30 minutes 45 seconds = 2 + (30 ÷ 60) + (45 ÷ 3600) = 2.5125 decimal hours
Common Time Calculation Scenarios
| Scenario | Operation | Example |
|---|---|---|
| Calculate total work hours | Time Between | 9:00 AM to 5:30 PM = 8.5 hours |
| Add overtime hours | Add Time | 8:00 hours + 2:30 hours = 10:30 hours |
| Calculate time remaining | Subtract Time | 4:00 hours - 1:45 hours = 2:15 hours |
| Convert to decimal for payroll | Any operation | 7 hours 45 minutes = 7.75 decimal hours |
| Project time tracking | Add Time | 2:30 + 3:15 + 1:45 = 7:30 hours total |