Time Duration Calculator
Calculate the exact duration between two clock times, in hours, minutes, and decimal hours.
Working out how much time falls between two clock readings is one of those calculations that's simple in theory and easy to get wrong by hand, especially once the span crosses midnight. This calculator takes a start time and an end time and returns the exact duration in hours and minutes, plus decimal hours for anything that needs a single number — timesheets, cooking or workout timing, travel duration, or just settling an argument about how long something actually took. If the end time is earlier than the start time, it's treated as spanning into the next day rather than producing a negative result.
Duration
8h 30m
8.50 decimal hours · 510 minutes total
How to Use This Calculator
1. Enter the start time
The time something began.
2. Enter the end time
The time it ended. If it's earlier than the start time, the calculator assumes it crossed midnight.
3. Read the duration
Shown as hours and minutes, decimal hours, and total minutes.
How It Works
duration = end_time − start_time (+24h if end_time < start_time)From 9:00 AM to 5:30 PM: 17:30 − 9:00 = 8 hours 30 minutes, or 8.5 decimal hours.
Frequently Asked Questions
How do I calculate hours between two times?
Subtract the start time from the end time. If the end time is earlier in the clock than the start time, add 24 hours first to account for the span crossing midnight, then subtract.
What's the difference between this and a work hours calculator?
This tool calculates the raw duration between any two clock times for any purpose. A work-hours-specific calculator additionally subtracts unpaid breaks and projects weekly or monthly totals for payroll — use this one for a quick general duration, and the Work Hours Calculator when you need the payroll-specific breakdown.
Can I use this for durations longer than 24 hours?
This tool is built for a single start and end clock time within one day (or crossing into the next day). For a duration spanning multiple full days, use the Days Between Dates calculator instead.
Common Mistakes
❌ Treating an overnight span as a negative or zero duration
If a shift or event runs from, say, 10:00 PM to 6:00 AM, subtracting the times directly gives a negative number. The correct duration crosses midnight and adds 24 hours before subtracting — this calculator does that automatically whenever the end time is earlier than the start time.
❌ Confusing decimal hours with hours and minutes
8 hours 30 minutes is 8.5 decimal hours, not 8.30 — the minutes portion needs to be divided by 60, not just moved after the decimal point. Payroll and invoicing software almost always wants the decimal format.
Related Tools
Work Hours Calculator With Lunch Break
Free work hours calculator with lunch break deduction. Enter start and end time to get decimal hours, total minutes, and weekly or monthly totals instantly.
Timesheet Calculator
Enter real clock-in and clock-out times for each day of the week and get your actual weekly total hours and gross pay — not a projection from a single day.
Days Between Dates Calculator
Free days between dates calculator with business day count. Get total days, weeks and days, months and days, and a month-by-month breakdown instantly.