Hours between two dates
Calculate the exact number of hours — and minutes, and seconds — between any two points in time.
How to calculate hours between two dates
The formula is simple: subtract the start timestamp from the end timestamp to get a duration in milliseconds, then divide by 3,600,000 (the number of milliseconds in an hour). The result is the total number of hours elapsed.
For example, from Friday at 9:00 AM to Monday at 5:00 PM is 80 hours — three full days (72 hours) plus 8 more hours. This tool handles the arithmetic instantly for any pair of dates you enter.
Common uses
- Timesheet calculations — total hours worked across a project or period
- Travel planning — hours between departure and arrival across time zones
- Billing — exact hours for hourly-rate invoices
- Fasting & health — hours since a meal or start of a fast
- Event planning — hours until a deadline or milestone
Hours vs. business hours
This calculator counts all hours — including nights, weekends, and holidays. If you need only working hours, use the business days calculator instead (it counts Mon–Fri days, which you can multiply by your hours-per-day).
Start noticing what matters.
Download Left on your iPhone to see the time you have left, dates you are looking forward to, build the habits you want to keep, and become a better version of yourself.
Scan with your camera to find Left on the App Store. Or search "Left" on the App Store.