Time Calculator — Add or Subtract Hours, Minutes, Seconds

Add or subtract two time values in HH:MM:SS form. Returns the result as HH:MM:SS, total decimal hours, and total seconds. Handles values longer than 24 hours.

Inputs

Result

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General calculation reads

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How to use this calculator

  • Enter Time A and Time B as hours, minutes, seconds (each input is bounded — minutes/seconds capped at 59, hours capped at 999).
  • Pick + Add or − Subtract.
  • Read the result in three formats. The decimal hours form is what most billing systems want (1:30:00 = 1.5 hr).
  • Subtraction can return negative results when Time B > Time A — useful for "how much over budget am I" calculations.

About this calculator

Pure time arithmetic — adding or subtracting two time values without converting to/from calendar dates. Useful for billable-hours math, lap-time summation, video editing, audio cue work, and any task where you need to add up clock-style durations. The result is shown in three equivalent forms: HH:MM:SS (clock form), decimal hours (billing form), and total seconds (data-entry form).

Frequently asked

How is this different from the Days Between Dates Calculator?+
Days Between Dates works on calendar dates (March 15 to April 20). Time Calculator works on pure durations (02:30:00 + 01:45:30). Use this one for "how long is the combined runtime of these 3 videos" or "if I bill 1h45m on task A and 2h10m on task B, what's my total".
Can I enter more than 24 hours?+
Yes — hours are capped at 999 to allow for week-long totals. The result preserves whatever value you compute (e.g., 50:00:00 stays as fifty hours, not 2 days 2 hours).
Why is the decimal-hours value useful?+
Time-tracking and billing systems usually accept decimal hours (1.5 hr) but reject HH:MM (1:30). Convert once here and copy-paste into Harvest, Toggl, QuickBooks, etc.
What happens when I subtract and B > A?+
The result is shown as negative (prefixed with −). Useful for budget-overage math: "I scheduled 2h, I worked 3h15m → 2:00:00 − 3:15:00 = −01:15:00 over."
Is there a way to multiply or divide time?+
Not in this calculator. For multiplying time (e.g., 8 reps × 1:30 each), enter the per-unit time and use a regular calculator on the seconds total (then convert back). We may add a multiply/divide mode in a future version if there's demand.

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