Time Calculator
Calculate a clock-time or duration result by adding or subtracting hours, minutes and seconds.
A time calculator helps you combine a starting time or duration with hours, minutes and seconds. It is useful for schedules, work sessions, travel planning, classes, workouts and everyday time calculations.
Enter the starting time or duration, choose Add or Subtract, enter the hours, minutes and seconds, then calculate the result. The calculator normalizes values automatically when minutes or seconds pass 60.
Time arithmetic is performed as seconds and then converted back into hours, minutes and seconds. When working with a clock time, results wrap across midnight when necessary.
This tool also fits into a wider set of practical utilities. Depending on what you are trying to calculate or measure next, you can continue with Time Addition Calculator, Time Subtraction Calculator, Time Difference Calculator, online stopwatch and 30 minute timer. For the complete collection, visit the utility tools homepage and choose another tool when your task changes.
How to use this calculator
- Enter your values. Select the dates or numbers required by the calculator.
- Check the inputs. Make sure the dates are in the order and range you intend to calculate.
- Calculate the result. The result appears instantly in the calculator above without submitting a form.
- Use the result. Apply the result to your schedule, deadline, planning or date calculation.
How the calculation works
Time arithmetic is performed as seconds and then converted back into hours, minutes and seconds. When working with a clock time, results wrap across midnight when necessary. The calculation is performed locally in your browser, so the page can return a result immediately after you change the inputs.
Things to know about date calculations
Calendar calculations can differ depending on whether a result is treated as an elapsed interval or an inclusive count. This site uses clear calendar-date rules and explains important assumptions where they affect the result. Business-day calculations on this page exclude weekends but do not automatically remove public holidays.
Frequently asked questions
How do I add hours and minutes to a time?
Enter the starting time, choose Add, enter the duration, and calculate the resulting time.
Can I subtract time?
Yes. Choose Subtract to work backward from a starting time or duration.
What happens when the result passes midnight?
The calculator wraps the clock result across midnight and shows the resulting time.