Time Duration Calculator
What is Time Duration Calculator
This time duration calculator works out how much time passes between two clock times, like 09:00 to 17:30, and returns the result in hours and minutes plus running totals. It also adds or subtracts a duration to any start time and tells you when the answer lands on the next or previous day. Overnight spans that cross midnight are handled, so a shift from 22:00 to 06:00 reads as 8 hours. Everything is pure clock math, with no dates or time zones involved.
How to use
- Pick Time between to measure the gap between a start and an end time.
- Enter the start time and the end time with the clock picker.
- Tick next day if the end time falls after midnight.
- Switch to Add / subtract to shift a start time by a set number of hours and minutes.
- Read the duration or the resulting time, with any day change shown beside it.
When to use it
Clocked in at 08:45 and out at 17:20 and need your hours? Enter both and you get 8 hours 35 minutes, ready for a timesheet or an invoice. The same tool tells you what time it is 90 minutes from now, or when a 22:30 departure lands after a 9-hour trip, without you counting on your fingers.
Frequently asked questions
How does it handle times that cross midnight?
If the end time is earlier than the start time, the calculator assumes the span crosses midnight and adds a day, so 22:00 to 06:00 returns 8 hours. You can also tick the next day box to force a full 24-hour offset even when the end looks later.
Can it add or subtract hours and minutes from a time?
Yes. Switch to the Add / subtract tab, enter a start time and a number of hours and minutes, and it returns the new time. If the result rolls into another day, it shows next day or the number of days beside the answer.
Does it use dates or time zones?
No. It works purely with clock times within a day, so there are no calendars or time zones. For the gap between two calendar dates, use the date difference calculator instead.
Can I share this tool with my inputs pre-filled?
Yes. The URL updates automatically as you type. Copy it from the address bar or use the Copy link button, and anyone who opens the link will see your exact inputs ready to go.
Related tools
A-a Gradient Calculator
Calculate the alveolar-arterial oxygen gradient from FiO2, PaO2 and PaCO2, and compare it to the expected value for age. Free and instant.
How Old Am I? Age Calculator
Find out exactly how old you are with this free age calculator. Enter your date of birth and get your age in years, months, days, zodiac sign, and more.
Anion Gap Calculator
Calculate the serum anion gap from sodium, chloride and bicarbonate, with optional potassium and albumin correction, to screen for metabolic acidosis.