How many seconds are in a day?

There are exactly 86,400 seconds in one day. The calculation is: 24 hours × 60 minutes × 60 seconds = 86,400 seconds.

How many seconds are in a week?

There are 604,800 seconds in one week (86,400 × 7 = 604,800).

How many milliseconds are in a day?

There are 86,400,000 milliseconds in one day (86,400 seconds × 1,000 milliseconds per second).

How Many Seconds in a Day? (86,400)

The Quick Answer

There are exactly 86,400 seconds in one day.

The math: 24 hours × 60 minutes × 60 seconds = 86,400.

Time Breakdown

Time Period	Hours	Minutes	Seconds
1 minute	0.0167	1	60
1 hour	1	60	3,600
6 hours	6	360	21,600
12 hours	12	720	43,200
1 day	24	1,440	86,400
1 week	168	10,080	604,800
1 month (30 d)	720	43,200	2,592,000
1 year (365 d)	8,760	525,600	31,536,000

Where This Comes Up

Programming

In computing, timestamps are often stored as seconds since an epoch (Unix time). Knowing there are 86,400 seconds per day is essential for date calculations.

Physics

Converting rates from per day to per second (or vice versa) is common. The Earth rotates once per 86,400 seconds (approximately).

Finance

Interest calculations sometimes use day counts converted to seconds for high-frequency trading systems.

Fun Fact

An actual solar day is not exactly 86,400 seconds. Due to tidal forces, days are gradually getting longer by about 2 milliseconds per century. Leap seconds are occasionally added to keep atomic clocks synchronized with Earth's rotation.

Use our time converter for any time conversion.