Time Calculator
Add or subtract two durations in hours, minutes, and seconds — and see the result converted into each unit.
How to add and subtract time
total seconds = h×3600 + m×60 + s
1h 45m + 0h 30m = 6,300s + 1,800s = 8,100s = 2h 15m (2.25 hours or 135 minutes).
A video editor has 3h 20m of raw footage and cuts 45m of unusable takes: 3h 20m − 45m = 12,000s − 2,700s = 9,300s = 2h 35m of final footage (2.5833 hours, or 155 minutes).
When to use this vs. the hours calculator
This tool adds and subtracts durations — total up lap times, combine task estimates, or find the difference between two lengths of time. If instead you want the hours worked between a clock-in and clock-out (minus lunch), the hours calculator is built for that. For calendar spans in days, use the date calculator. Note that subtracting a larger time from a smaller one gives a negative duration, shown here as a signed result.
Common time-math mistakes
- Mixing up clock times with durations. This tool adds pure lengths of time, not times of day — entering "5:30" meaning 5:30 PM will be read as 5 hours 30 minutes, not a time of day. For a clock-in-to-clock-out span, use the hours calculator instead.
- Dropping the negative sign on a subtraction. When the second duration is larger than the first, the result is negative (e.g., 1h − 2h = −1h) — losing that minus sign flips the meaning, such as reporting "ahead of schedule" when the real result was "behind schedule."
- Rounding minutes or seconds before adding, instead of after. Rounding 44.6 minutes down to 44 before combining it with other durations introduces error that compounds every time you repeat the shortcut — round only the final total.
Frequently asked questions
How do I add hours and minutes together?
Add each unit and carry: 60 seconds → a minute, 60 minutes → an hour. 1h45m + 30m = 2h15m.
How do I convert minutes to hours?
Divide by 60. 90 minutes = 1.5 hours.
How is this different from the hours calculator?
This adds/subtracts durations; the hours calculator finds time worked between clock-in and clock-out.
Can I add more than two durations at once?
Chain results: add the first two, then use the total as one side of a second calculation. For many short intervals, converting each to seconds and adding by hand is often faster.
How do I handle durations longer than 24 hours?
Just enter hours greater than 24 — no need to convert to days. 30h15m + 6h = 36h15m.
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Last reviewed: September 2026.