Time Calculator Online Free Tool
Time Calculator
Time Arithmetic
Calculation Result
Enter time values to see the calculation result
The time calculator adds and subtracts hours, minutes, and seconds. Add a duration to a start time to find when something ends, or subtract two times to find the elapsed duration. It handles all time arithmetic, including calculations that cross midnight or span multiple days. Common uses include scheduling tasks, calculating meeting durations, tracking workout times, and determining when a process will finish.
Time Arithmetic
Time operates in a mixed-base system: base-60 for seconds and minutes (60 seconds per minute, 60 minutes per hour), and base-24 for hours (24 hours per day). This makes time arithmetic more complex than regular decimal arithmetic because you carry at 60, not at 10. When adding times, always work from the smallest unit up and carry the overflow to the next unit.
Add: Combine each unit, convert up when totals exceed base (60 or 24) Subtract: Borrow from higher units when needed Example: 3:45:30 + 1:25:45 Seconds: 30+45=75 → 15s + 1min carry Minutes: 45+25+1=71 → 11min + 1hr carry Hours: 3+1+1=5 Result: 5:11:15
Common Time Conversions
Converting time units requires multiplying or dividing by 60 (for minutes-seconds and hours-minutes) or 24 (for hours-days). Decimal hours are used in many payroll and project management systems: 1 hour 30 minutes = 1.5 hours, 45 minutes = 0.75 hours.
| From | To Seconds | To Minutes | To Hours |
|---|---|---|---|
| 1 minute | 60s | 1 min | 0.0167 hr |
| 1 hour | 3,600s | 60 min | 1 hr |
| 1 day | 86,400s | 1,440 min | 24 hr |
| 1 week | 604,800s | 10,080 min | 168 hr |
| 1 month (avg) | 2,629,800s | 43,830 min | 730.5 hr |
| 1 year (365 days) | 31,536,000s | 525,600 min | 8,760 hr |
Decimal Hours vs Hours:Minutes
Many payroll systems and timesheet software use decimal hours rather than hours:minutes format. To convert minutes to decimal hours, divide minutes by 60. To convert decimal hours back to minutes, multiply the decimal portion by 60. This conversion is important when multiplying hours by an hourly rate to calculate pay.
Minutes to decimal hours: minutes / 60 Example: 2 hours 45 minutes = 2 + 45/60 = 2.75 hours Decimal hours to HH:MM: Take the decimal portion × 60 = minutes Example: 3.4 hours = 3 hours + (0.4 × 60) = 3 hours 24 minutes
7 hours 30 minutes × $18/hour: first convert to 7.5 hours. Pay = 7.5 × $18 = $135.
Time Zones and UTC
Coordinated Universal Time (UTC) is the global time standard against which all time zones are defined. Time zone offsets are expressed as UTC+X or UTC-X. When calculating time differences between locations, convert both times to UTC first, then subtract. Daylight saving time shifts some zones by +1 hour seasonally, which can cause confusion when scheduling across time zones during the spring-forward and fall-back transitions.
| City | Time Zone | UTC Offset (Standard) |
|---|---|---|
| New York | EST / EDT | UTC-5 / UTC-4 |
| London | GMT / BST | UTC+0 / UTC+1 |
| Paris | CET / CEST | UTC+1 / UTC+2 |
| Dubai | GST | UTC+4 (no DST) |
| Mumbai | IST | UTC+5:30 (no DST) |
| Tokyo | JST | UTC+9 (no DST) |
| Sydney | AEST / AEDT | UTC+10 / UTC+11 |
Frequently Asked Questions
How do I add 90 minutes to 11:45 AM?⌄
11:45 AM + 90 minutes. Convert 90 minutes to 1 hour 30 minutes. Add: 11:45 + 1:30. Minutes: 45 + 30 = 75, which is 1 hour 15 minutes. Hours: 11 + 1 + 1 carry = 13:15 in 24-hour time = 1:15 PM. Alternatively, think of it in steps: 11:45 + 15 minutes = 12:00 noon, then add the remaining 75 minutes: 12:00 + 1:15 = 1:15 PM.
How do I calculate the time difference between two time zones?⌄
Find the UTC offset for each time zone, then subtract to get the difference. New York (EST) is UTC-5, Tokyo (JST) is UTC+9. Difference = 9 - (-5) = 14 hours. Tokyo is 14 hours ahead of New York. If it is 9:00 AM Monday in New York, it is 11:00 PM Monday in Tokyo. Note that during daylight saving time, US Eastern switches to UTC-4, making the difference 13 hours.
How many seconds are in a year?⌄
31,536,000 seconds in a common year (365 × 24 × 60 × 60 = 31,536,000). A leap year has 31,622,400 seconds (366 days × 86,400 seconds). The approximation "pi times 10 million" (about 31.4 million) is sometimes used in physics as a quick estimate. For precision work, the tropical year (time for Earth to orbit the sun) is 365.2422 days, giving 31,556,926 seconds.
What is the 24-hour clock (military time)?⌄
24-hour time runs from 00:00 (midnight) to 23:59. It eliminates AM/PM ambiguity, which is why it is used in military, aviation, healthcare, and international contexts. To convert 12-hour to 24-hour: 12:00 AM (midnight) = 00:00, 1:00 AM through 12:59 PM stay the same as 01:00 through 12:59, then 1:00 PM through 11:59 PM add 12 (1:00 PM = 13:00, 6:30 PM = 18:30, 11:59 PM = 23:59).
How do I calculate elapsed time when the clock crosses midnight?⌄
When start time is before midnight and end time is after midnight, add 24 hours to the end time before subtracting. Example: start 10:30 PM (22:30), end 6:00 AM (06:00). Add 24 to end: 06:00 + 24:00 = 30:00. Elapsed = 30:00 - 22:30 = 7:30 (7 hours 30 minutes). The time calculator handles this automatically, but knowing the manual method helps you verify the result.