Time Calculator: Add or Subtract Hours, Minutes, Seconds
Add or subtract time durations with automatic carry-over. Row input (hours, minutes, seconds per row), expression shorthand (1h 30m + 45m), or add/subtract from a date and time. Payroll decimals, project totals, and scheduling. Free, runs locally.
Add or Subtract Time: Durations or from a Date
Choose your mode: Duration (add or subtract time values using rows or an expression), or Add/Subtract from Date (shift a specific datetime). In Duration mode, use Rows to enter hours, minutes, and seconds per rowโAdd sums all rows, Subtract takes the first row minus the restโor use Expression for shorthand like
1h 30m + 45m or 2d - 1h 20m. In Date mode, pick a start datetime, then enter days, hours, minutes, and seconds to add or subtract. Copy the result with one click.Sexagesimal System & Carry-Over
Time uses base 60: . When you add durations, excess units roll up: 65 minutes becomes 1 hour 5 minutes; 90 seconds becomes 1 minute 30 seconds. The calculator normalizes everything internallyโyou can even enter 2h 65m 90s and get 3h 6m 30s.
Expression Parser
In Expression mode, type units with numbers:
d for days, h for hours, m for minutes, s for seconds. Combine with + and โ. Examples: 1h 30m + 45m โ 2h 15m; 2d - 1h 20m โ 1 day, 22 hours, 40 minutes. The parser updates as you type.Negative Duration & Copy Result
If you subtract a larger duration from a smaller one (e.g., 1 hour minus 2 hours), the calculator shows "Negative Time Difference" and displays the magnitude with a minus sign. Use the Copy Result button to paste the human-readable string (e.g., "3 Hours, 15 Minutes, 0 Seconds" or "Wednesday, Feb 18, 2026 at 10:05 PM") into emails, spreadsheets, or reports.
Time Calculator FAQ
How do I add or subtract time?
In Duration mode, use the row inputs (hours, minutes, seconds per row) or Expression mode (e.g. 1h 30m + 45m or 2d - 1h 20m) to add or subtract time valuesโAdd sums all rows; Subtract takes the first row and subtracts the rest. To add or subtract time from a specific date and time, switch to Add/Subtract from Date mode, pick your start datetime, then enter days, hours, minutes, and seconds. Results show the total duration or the new date and time with automatic carry-over.
How do I add two time durations?
In Duration mode, enter hours, minutes, and seconds for each row and choose Add (+). The result shows the summed duration with automatic carry-overโe.g., 65 minutes becomes 1 hour 5 minutes. Or switch to Expression mode and type something like
1h 30m + 45m for instant results.What happens when I subtract a larger time from a smaller one?
The calculator displays "Negative Time Difference" and shows the absolute duration with a minus sign (e.g., โ1 Hour, 30 Minutes, 15 Seconds). You get both the sign and the magnitude, which helps when tracking overtime or backward counts.
Why does time use 60 for minutes and seconds?
Time uses a sexagesimal (base-60) system inherited from ancient Babylonian astronomy. The rule: โsame logic as clock faces and angular degrees.
Can I add time to a specific date and time?
Yes. Switch to Add/Subtract from Date mode. Pick a start date and time (using the datetime picker), then enter days, hours, minutes, and seconds to add or subtract. The result shows the exact date and timeโuseful for deadlines, reminders, or scheduling.
How does Expression mode work?
In Expression mode, type durations like
1h 30m + 45s or 2d - 1h 20m. Use d (days), h (hours), m (minutes), s (seconds) with + and โ. The parser updates in real time. Handy for quick totals without entering each value separately.