There are 86,400 seconds in 24 hours. This calculation is based on the fact that there are 60 seconds in a minute, 60 minutes in an hour, and 24 hours in a day. So, to convert hours to seconds, you multiply the number of hours by 60 (to convert to minutes), then multiply by 60 again (to convert to seconds). Therefore, 24 hours is equal to 24 * 60 * 60 = 86,400 seconds.