How Many Seconds Are in a Day?
Discover how many seconds are in a 24-hour day (86,400 seconds). Understand leap seconds, computer epoch math, and solar time with an interactive calculator.
1 day in All Units
86,400 Seconds: The Fundamental Computer & Solar Constant
A standard calendar day consists of exactly 86,400 seconds. This is computed by multiplying 24 hours by 60 minutes (1,440 minutes) and then by 60 seconds.
In computer science, Unix epoch timestamps increment by 86,400 every single standard calendar day. While astronomical Earth rotation fluctuates slightly (occasionally requiring leap seconds), civil clocks define 86,400 SI seconds per day.
Step-by-Step Calculation
- 24 hours per day.
- Multiply by 3,600 seconds per hour: 24 × 3,600 = 86,400 seconds.
- 1 week = 86,400 × 7 = 604,800 seconds.
Frequently Asked Questions
How many seconds are in 24 hours?
There are exactly 86,400 seconds in 24 hours (24 × 60 × 60 = 86,400).
How many seconds are in a 7-day week?
There are 604,800 seconds in a week (7 × 86,400 = 604,800).
What is a leap second?
A leap second is a 1-second adjustment occasionally applied to UTC time to keep atomic clocks synchronized with Earth's slowing rotation.