⏱ Time Tool

Time Calculator

Add or subtract hours, minutes & seconds — plus convert any duration into other time units instantly.

First duration

Hours

Min

Sec

Second duration

Hours

Min

Sec

⏱ Result

-- HH : MM : SS

--Seconds

--Minutes

--Hours

--Days

Full unit breakdown

Milliseconds--

Total Seconds--

Total Minutes--

Total Hours--

Total Days--

Total Weeks--

💡

Quick fact

History

No calculations yet.

Results use exact integer arithmetic — no floating-point errors. Decimals in the breakdown are rounded to 6 places.

How does this time calculator work?

All inputs are converted to total seconds, the operation is applied, then the result is converted back to HH:MM:SS — with zero floating-point error. The unit breakdown derives every other unit from that final second count.

Total Seconds = (H × 3600) + (M × 60) + S
Result = Seconds_A ± Seconds_B
Back to HH:MM:SS: H = ⌊Result ÷ 3600⌋ · M = ⌊(Result mod 3600) ÷ 60⌋ · S = Result mod 60

⏱ Adding durations

Perfect for summing work sessions, workout segments, or video clips. Carry-over from seconds to minutes to hours is automatic.

🔄 Subtracting time

Find the difference between two durations — scheduled vs actual. Negative results display in red with a full unit breakdown.

📐 Unit Converter

Type any value in any unit — milliseconds through weeks — and all others update instantly, bidirectionally.

📋 History & Copy

Last 10 calculations saved per session. Click any history row to restore it. Copy button formats results for pasting anywhere.

Frequently asked questions

How do I add two time durations?

Enter hours, minutes and seconds for both durations, keep "Add" selected, then click Calculate. Carry-over from seconds into minutes and from minutes into hours is handled automatically.

Can the result be negative?

Yes — if you subtract a larger time from a smaller one the result is negative. It appears in red with a minus sign, and the unit breakdown shows the absolute values with a − prefix.

How many seconds are in an hour?

There are exactly 3,600 seconds in one hour (60 minutes × 60 seconds). Switch to the Unit Converter tab, type 1 in the Hours field, and all conversions appear instantly.

How do I convert hours to minutes?

Multiply hours by 60. For example, 2.5 hours = 150 minutes. The Unit Converter tab handles any value bidirectionally across milliseconds, seconds, minutes, hours, days, and weeks.

What is the difference between duration and clock time?

Duration is a span of time like 1 hour 30 minutes. Clock time is a specific moment like 14:30. This calculator works with durations — ideal for project tracking, workouts, video editing, or travel.