Time Calculator
Calculate the time between two times in hours, minutes, and seconds. Also add or subtract time from any starting time. Free time duration calculator.
Reviewed for accuracy by Marcus Webb and the Blueprint Dynamics editorial team (last updated July 2026). Our calculators use primary-source formulas and are cross-checked against IRS publications, Fannie Mae guidelines, and Federal Reserve data. Learn more about our methodology.
09:00 to 17:30
8 hr 30 min
Hours
8
Minutes
30
Seconds
0
What the time calculator computes
The time calculator adds and subtracts time durations, converts between time units, and determines elapsed time between two clock times. Time arithmetic is more complex than regular arithmetic because time uses a base-60 system (60 seconds per minute, 60 minutes per hour) rather than base-10. Adding 2 hours 45 minutes and 1 hour 30 minutes doesn't equal 3 hours 75 minutes — it equals 4 hours 15 minutes after carrying the 75 minutes as 1 hour 15 minutes.
Common uses
Work hours and payroll: summing hours worked across multiple days or shifts. Overtime calculation: when does an employee cross 40 hours in a week? Project time tracking: total billable hours across multiple time entries. Travel planning: add layover times, travel durations, and time zone shifts. Sports and fitness: pace calculations (minutes per mile), race time projections, interval training totals. Video and audio editing: total runtime calculations for playlists, podcasts, or video projects. Cooking and baking: adding prep time, cooking time, and rest time to determine when to start.
Time zone arithmetic
When working across time zones, add or subtract the UTC offset difference. New York (EST, UTC−5) to London (GMT, UTC+0): add 5 hours to New York time to get London time. During US daylight saving (EDT, UTC−4): add 4 hours. US daylight saving runs March–November; UK daylight saving (BST, UTC+1) runs a slightly different schedule, causing the offset to shift twice a year. For precise cross-timezone scheduling, always use UTC as the reference point and convert both times to UTC before comparing.
Decimal hours vs. hours and minutes
Payroll and billing systems often use decimal hours rather than hours:minutes format. 1.5 hours = 1 hour 30 minutes. 0.25 hours = 15 minutes. To convert from hours:minutes to decimal: decimal = hours + (minutes / 60). 2 hours 20 minutes = 2 + (20/60) = 2.333 hours. To convert from decimal to hours:minutes: whole number is hours, decimal × 60 gives minutes. 3.75 hours = 3 hours + (0.75 × 60) = 3 hours 45 minutes. Most time tracking and invoicing software accepts decimal hours — understanding the conversion prevents billing errors.