Time Duration Calculator (Hours, Minutes, Seconds)
Add or subtract time durations in hours, minutes, and seconds. Useful for video editing, project tracking, and time math.
What this calculates
Time math is tricky in your head — adding 1:35:42 + 0:48:30 isn't intuitive. This calculator handles addition and subtraction of times in HH:MM:SS format, perfect for editing video timelines, summing race splits, or calculating total work time across multiple entries.
Formula & how it works
Convert each time to total seconds: total = h × 3600 + m × 60 + s. Add or subtract totals. Convert back: hours = total ÷ 3600, remainder ÷ 60 for minutes, remainder for seconds. Handle negative results (when subtracting larger from smaller) with absolute value plus sign indicator.
Worked example
1:35:42 + 0:48:30. Convert: 5,742 + 2,910 = 8,652 sec. Back: 8,652 ÷ 3600 = 2 hr, remainder 1,452 ÷ 60 = 24 min, remainder 12 sec. Result: 2:24:12. Subtract example: 2:30:00 − 1:45:30 = 9000 − 6330 = 2670 sec = 0:44:30.
Frequently asked questions
Decimal hours conversion?
1 hour 30 minutes = 1.5 decimal hours. Common in payroll/billing. 45 minutes = 0.75 hr. To convert: minutes ÷ 60 + hours. Decimal hours are easier for math but worse for clock display.
What about days?
1 day = 24 hours = 86,400 seconds. Add a day field if needed: 1 day 5:30:00 = 29:30:00. Most calculators stick to hours-minutes-seconds; only durations over 24 hr need days explicitly.
Can I subtract a larger time?
Result is negative — show with a minus sign. Common in race time predictions ('how much faster do I need to go') and project deadline math ('how much time am I over').
Milliseconds?
Some use cases (track-and-field, video editing) need them. Multiply seconds by 1000 to convert; format MS:MS.mmm or HH:MM:SS.mmm. This calculator stays at second precision.
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