Conversion formula

The conversion factor from hours to seconds is 3600, which means that 1 hour is equal to 3600 seconds:

1 hr = 3600 s

To convert 21 hours into seconds we have to multiply 21 by the conversion factor in order to get the time amount from hours to seconds. We can also form a simple proportion to calculate the result:

1 hr → 3600 s

21 hr → T_(s)

Solve the above proportion to obtain the time T in seconds:

T_(s) = 21 hr × 3600 s

T_(s) = 75600 s

The final result is:

21 hr → 75600 s

We conclude that 21 hours is equivalent to 75600 seconds:

21 hours = 75600 seconds

Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 second is equal to 1.3227513227513E-5 × 21 hours.

Another way is saying that 21 hours is equal to 1 ÷ 1.3227513227513E-5 seconds.

Approximate result

For practical purposes we can round our final result to an approximate numerical value. We can say that twenty-one hours is approximately seventy-five thousand six hundred seconds:

21 hr ≅ 75600 s

An alternative is also that one second is approximately zero times twenty-one hours.

Conversion table

hours to seconds chart

For quick reference purposes, below is the conversion table you can use to convert from hours to seconds