Time Calculator

What Is a Time Calculator?

Time arithmetic is awkward because it uses base-60 (60 seconds in a minute, 60 minutes in an hour) rather than base-10. Adding 45 minutes to 1 hour 30 minutes requires carrying over at 60 rather than 100, which catches many people out when doing it mentally. This calculator handles the base-60 maths for you, giving clean results in hours, minutes, and seconds.

The time-between mode is useful for calculating shift lengths, billable hours, travel times, and cooking durations. Enter a start time and end time to see the exact duration. The add/subtract mode lets you combine multiple durations — for example, adding up task times to see if they fit within a deadline, or subtracting elapsed time from a countdown.

Common uses include calculating total hours worked in a week for payroll, determining how long a flight takes across time zones, timing exam sections, and planning event schedules. The calculator handles overnight periods (when the end time is earlier than the start time) by assuming the end time is the following day.

How Do You Use This Time Calculator?

To add or subtract durations, enter hours, minutes, and seconds for each value. To find time between two times, enter the start and end times. Click Calculate to see the result.

1. Choose the calculation mode: add durations, subtract durations, or find time between.
2. For time between: enter the start time and end time in HH:MM or HH:MM:SS format.
3. For adding: enter two or more durations in hours, minutes, and seconds.
4. For subtracting: enter the larger duration first, then the amount to subtract.
5. Click Calculate to see the result in hours, minutes, and seconds.
6. Review the result and use it for scheduling, billing, or planning.

How Does the Time Calculator Formula Work?

The formula used: Time Difference = End Time − Start Time; Duration Sum = Time₁ + Time₂ (carrying over 60 seconds = 1 minute, 60 minutes = 1 hour)

What Are Some Example Calculations?

Time between 09:15 and 17:42 = 8 hours 27 minutes. Adding 2h 45m + 1h 30m = 4 hours 15 minutes.

When Should You Use a Time Calculator?

Use the time calculator whenever you need to add durations, subtract time periods, or find the gap between two clock times. Freelancers and contractors use it to total billable hours from start and end times. Project managers use it to check whether a series of tasks fits within a deadline. Parents use it to calculate how long until an event or pickup time.

The calculator is also handy for international coordination. If a meeting starts at 14:00 GMT and you need to prepare for 2 hours 30 minutes beforehand, the calculator tells you to start at 11:30 GMT. For recurring time calculations like weekly timesheets, use the tool to verify totals before submitting.

What Do These Terms Mean?

What Are the Best Tips to Know?

• For overnight calculations, the tool automatically handles times that cross midnight.
• When totalling a week's work hours, calculate each day separately and then add the daily totals.
• Convert fractional hours to minutes for more intuitive results: 0.75 hours = 45 minutes.
• Use 24-hour format to avoid AM/PM confusion, especially for international time calculations.
• Double-check time zone conversions separately — this calculator works with local times, not time zones.

What Mistakes Should You Avoid?

• Subtracting minutes directly without borrowing from hours when the end minutes are less than the start minutes.
• Forgetting to account for lunch breaks or other unpaid time when calculating work shift durations.
• Treating time as base-10: writing 1.5 hours as 1h 50m instead of 1h 30m.
• Not specifying AM or PM when using 12-hour format, leading to a 12-hour error in the calculation.