Time Calculator

Add or subtract two time durations (hours and minutes) and see the result in hours:minutes, plus totals in minutes, decimal hours, and seconds.

Quick Facts

Method
Convert each time to total minutes, then add or subtract
1 hour = 60 minutes = 3,600 seconds.
Base-60
Clock time carries over at 60, not 10
75 minutes becomes 1h 15m, the same way 75 cents carries to a dollar.

Your Results

Calculated
Result (H:M)
-
Time A ± Time B
Total minutes
-
Result expressed in minutes
Total hours (decimal)
-
Result as a decimal hour value
Total seconds
-
Result expressed in seconds

Ready

Enter two time durations and choose add or subtract.

About the Time Calculator

This calculator adds or subtracts two time durations given in hours and minutes — for example, "how long is 2h 45m plus 1h 20m?" or "what's left if I subtract 1h 20m from 2h 45m?" It uses the standard method for time arithmetic: convert every duration to a single unit (minutes), do ordinary addition or subtraction on those numbers, then convert the result back into hours and minutes.

The formula

For a duration of H hours and M minutes, the total in minutes is:

  • Total minutes = H × 60 + M

Once both Time A and Time B are converted this way, the calculator adds or subtracts the two totals: Result (minutes) = Total A ± Total B. To turn that back into hours and minutes, divide by 60 and keep the remainder:

  • Result hours = floor(Result minutes ÷ 60)
  • Result minutes (remainder) = Result minutes mod 60

From the same total-minutes value, seconds and decimal hours follow directly: seconds = minutes × 60, and decimal hours = minutes ÷ 60.

Why convert to minutes first

Clock time is a base-60 (sexagesimal) system, not base-10, so you cannot add "2 hours 45 minutes" and "1 hour 20 minutes" by simply adding the hour digits and the minute digits when the minutes overflow 59. Converting everything to one unit (minutes) sidesteps the carrying rules during the addition itself — the carry only has to be handled once, when converting the total back to hours and minutes at the end.

Worked example

Add 2h 45m and 1h 20m: Total A = 2 × 60 + 45 = 165 minutes. Total B = 1 × 60 + 20 = 80 minutes. Sum = 245 minutes. Converting back: 245 ÷ 60 = 4 remainder 5, so the result is 4h 5m — equivalently 245 minutes, 4.08 decimal hours, or 14,700 seconds.

Common uses

  • Timesheets and payroll: adding worked hours across shifts, or converting hours and minutes to decimal hours for billing.
  • Cooking and recipes: combining prep time and cook time, or figuring out how much time remains.
  • Workouts and training: summing interval or lap times.
  • Scheduling: finding how much time is left between tasks, or how long a combined block of meetings runs.

Precision note

This calculator performs pure duration arithmetic — it does not account for clock-time wraparound (like crossing midnight), time zones, or calendar effects (different month lengths, leap years). For calculating the difference between two calendar dates and times, use a dedicated time-between-dates tool instead.

Frequently Asked Questions

How does a time calculator add or subtract durations?
Each time is converted into a single unit — total minutes — by multiplying the hours by 60 and adding the minutes. The two totals are then added or subtracted, and the result is converted back into hours and minutes by dividing by 60 (the whole number of hours) and taking the remainder (the minutes).
What happens if I subtract a larger time from a smaller one?
The result is negative. For example, 1h 20m minus 2h 45m is -1h 25m, meaning Time B is 1 hour and 25 minutes longer than Time A. The calculator shows a leading minus sign on the result and on the total minutes, hours, and seconds.
How do I convert the result into seconds or decimal hours?
Multiply the total minutes by 60 to get seconds. Divide the total minutes by 60 to get decimal hours — for example, 245 minutes is 245 / 60 = 4.08 hours. Decimal hours are useful for payroll and billing, where time is often recorded as a fraction of an hour rather than in hours and minutes.
Why do minutes carry over at 60 instead of 10?
Clock time uses a base-60 (sexagesimal) system inherited from ancient Babylonian mathematics, not the base-10 system used for ordinary arithmetic. Because of this, 45 minutes plus 30 minutes is not 75 minutes on a clock face — it carries over to 1 hour and 15 minutes, the same way 75 cents carries over to a dollar in a base-100 currency.

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