## Conversion formula

The conversion factor from days to hours is 24, which means that 1 day is equal to 24 hours:

1 d = 24 hr

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

1 d → 24 hr

21 d → T(hr)

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

T(hr) = 21 d × 24 hr

T(hr) = 504 hr

The final result is:

21 d → 504 hr

We conclude that 21 days is equivalent to 504 hours:

21 days = 504 hours

## Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 hour is equal to 0.001984126984127 × 21 days.

Another way is saying that 21 days is equal to 1 ÷ 0.001984126984127 hours.

## Approximate result

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

21 d ≅ 504 hr

An alternative is also that one hour is approximately zero point zero zero two times twenty-one days.

## Conversion table

### days to hours chart

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

days (d) hours (hr)
22 days 528 hours
23 days 552 hours
24 days 576 hours
25 days 600 hours
26 days 624 hours
27 days 648 hours
28 days 672 hours
29 days 696 hours
30 days 720 hours
31 days 744 hours