Time Calculator
Add or subtract hours, minutes, and seconds, find the duration between two times, multiply or divide a time value, and convert between time units. Perfect for scheduling, cooking, editing, sports timing, and project planning — works worldwide.
Choose a mode — add or subtract a list of times, measure the duration between two clock times, multiply/divide a time, or convert time units. Enter values and the result updates instantly.
Enter hours, minutes, and seconds for each row. Choose + to add or − to subtract.
* This calculator performs exact time arithmetic and unit conversions. For work-shift totals with breaks, overtime, and pay, use our Hours Calculator; for differences measured in days, use our Date Calculator. Time-zone offsets and daylight-saving changes are not applied.
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What Is a Time Calculator?
A time calculator is a free online tool for doing arithmetic with time — something that's surprisingly error-prone by hand because time isn't decimal (there are 60 seconds in a minute and 60 minutes in an hour, not 100). It lets you add and subtract hours, minutes, and seconds, find the duration between two clock times, multiply or divide a time value, and convert between days, hours, minutes, and seconds.
This tool is built for everyday time math: adding up task durations, working out how long until something, timing laps or workouts, planning cooking stages, editing audio and video, or totalling billable time. For work shifts with breaks and pay, see our Hours Calculator; for differences in days and weeks, see our Date Calculator.
How to Use This Time Calculator
- Pick a mode — add/subtract, duration between two times, multiply/divide, or convert.
- Enter your time values — hours, minutes, and seconds, or two clock times.
- Choose + or − for each row when adding and subtracting.
- Read the result — shown in h:m:s, decimal hours, total minutes, and more.
How to Add Time (Hours, Minutes & Seconds)
The reliable way to add or subtract time is to convert everything to a single unit — seconds — do the arithmetic, then convert back:
Then: Hours = Total ÷ 3600, remainder → Minutes ÷ 60, remainder → Seconds
Example: add 2 h 45 m and 1 h 30 m. In seconds: (2×3600 + 45×60) + (1×3600 + 30×60) = 9,900 + 5,400 = 15,300 seconds = 4 h 15 m. Doing it digit-by-digit in your head is where mistakes creep in; the calculator handles the "carrying" of 60s automatically.
How to Calculate Duration Between Two Times
To find how long is between two clock times, convert both to seconds since midnight and subtract. If the end time is earlier than the start (an overnight span), add 24 hours:
Example: from 9:00 to 17:30 is 8 hours 30 minutes. From 22:00 to 6:00 crosses midnight, so it's 8 hours. The "duration between" mode does this for you, with an overnight option.
How to Multiply or Divide Time
Sometimes you need a multiple of a duration — like 8 laps at 1 minute 45 seconds each, or splitting a 3-hour task into 4 equal blocks. Multiply or divide the total seconds, then convert back:
- 8 × 1:45 = 8 × 105 seconds = 840 seconds = 14 minutes.
- 3:00:00 ÷ 4 = 10,800 ÷ 4 = 2,700 seconds = 45 minutes each.
Converting Time Units
The calculator converts between days, hours, minutes, and seconds instantly. Handy reference points:
| Unit | Seconds | Minutes | Hours |
|---|---|---|---|
| 1 minute | 60 | 1 | 0.0167 |
| 1 hour | 3,600 | 60 | 1 |
| 1 day | 86,400 | 1,440 | 24 |
| 1 week | 604,800 | 10,080 | 168 |
For example, 150 minutes equals 2 hours 30 minutes, or 2.5 decimal hours, or 9,000 seconds.
Why Time Math Is Tricky (the 60, Not 100, Problem)
Most arithmetic uses base-10, but time uses base-60 for seconds and minutes and base-24 for hours. That means you can't just add the numbers like decimals — 1.45 hours is not 1 hour 45 minutes (it's 1 hour 27 minutes). Mixing up decimal hours and "hours and minutes" is the most common time-math error, which is exactly why a dedicated calculator is so useful.