Result (HH:MM:SS)—
Result (Decimal Hours)—
Result (HH:MM:SS)—
Result (Decimal Hours)—
As Decimal Hours—
As Total Minutes—
As HH:MM:SS—
As Total Seconds—
List Total (HH:MM:SS)—
List Total (Decimal Hours)—
Example Data Table
| # | Task | Duration (HH:MM:SS) | Decimal Hours |
|---|---|---|---|
| 1 | Planning | 0:45:00 | 0.75 |
| 2 | Design | 1:30:00 | 1.5 |
| 3 | Development | 3:15:30 | 3.2583 |
| 4 | Testing | 1:05:00 | 1.0833 |
| 5 | Documentation | 0:40:00 | 0.6667 |
| 6 | Review | 0:50:30 | 0.8417 |
| Total | |||
Formulas Used
- Parsing to seconds:
totalSeconds = hours×3600 + minutes×60 + seconds - Add/Subtract: Convert each duration to seconds, then add or subtract. Normalize back to HH:MM:SS with carrying and borrowing across units.
- Multiply/Divide:
scaledSeconds = round(totalSeconds × factor)orround(totalSeconds ÷ factor), then convert back to HH:MM:SS. - Decimal Hours:
Hdec = H + M/60 + S/3600 - Total Minutes:
Mtotal = H×60 + M + S/60 - HH:MM:SS from seconds: Divide by 3600 for hours, mod remainder for minutes, and seconds; keep sign if negative.
How to Use This Calculator
- Pick a tab that matches your task: add/subtract, multiply/divide, convert, or sum a list of durations.
- Enter times as
HH:MMorHH:MM:SS. Partial seconds are rounded to the nearest second. - For subtraction, choose which way the difference should be computed using the Operation menu.
- For factors, decimals are supported (e.g., ×1.25). Results are displayed as HH:MM:SS and decimal hours.
- Use the Example Data Table for a reference workload and download CSV/PDF for records or sharing.
- Update your own project tasks in “Sum a List,” then mirror them in the example table to visualize in the chart.
- All calculations are performed in your browser for speed; no data is sent anywhere.
FAQs
Yes. You can use
HH:MM and the calculator assumes :00 seconds.Negative durations are shown with a leading minus sign, e.g.,
-0:15:00.Hours can be large; minutes and seconds should be 0–59 for standard HH:MM:SS formatting.
Yes. Enter either HH:MM:SS or decimal hours; the other formats update instantly.
Use the CSV and PDF buttons above the table to download your data for records or sharing.
All math is done in seconds internally. Decimal hours are shown to four decimals in the example table.
No. Everything runs locally in your browser. For records, export CSV or PDF.
Quick Tips
- Use a colon to separate hours, minutes, and seconds.
- Spaces are ignored—
2 : 5 : 3is treated as2:5:3. - For payroll-style rounding, scale with Multiply/Divide as needed.
- Use the Sum tab for rolling up daily timesheets.
About the chart
The bar chart visualizes hours per task from the Example Data Table. Edit the table in code or rebuild it from your own list to update the chart.