Days to Seconds Converter

When to use days → seconds

Days to seconds multiplies by 86 400 (24 × 3600). A 7-day expiry is 604 800 seconds; a 30-day token lifetime is 2 592 000 seconds. This is the conversion every developer performs when a policy written in days must be entered into a config field that takes seconds. Watch the next step: many APIs actually want milliseconds, making a day 86 400 000 ms — the off-by-1000 between the two is a classic source of near-instant expiries or effectively immortal sessions.

Satellite mission planners schedule orbital manoeuvres in days on a calendar but feed thruster-burn timing to onboard systems in seconds: a 2 d hold before a burn is 172800 s, and a 0.5 d window is 43200 s. Because spacecraft clocks and ground-station scripts operate on second-resolution timestamps, every day-level planning figure gets expanded to seconds before it reaches the actual command sequence.

How to convert days to seconds

1. 1

   Take your value

   Start with your value in days.

2. 2

   Multiply by 86400

   Multiply the day value by 86400. This is the exact conversion factor from days to seconds.

3. 3

   Read the result

   The product is your value in seconds. For example, 5 d × 86400 = 432000 s.

Conversion formula

The exact factor from days to seconds is 86400.

Seconds = Days × 86400

Days to Seconds conversion table

Fifty common reference values, hand-picked for skim utility. Use the calculator above for any value not listed.

Real-world reference

One Earth rotation is 1 d. A standard rental period is often 1 d. In seconds, that gives you: 1 d = 86400 s, 10 d = 864000 s, 100 d = 8640000 s.

Frequently asked questions

How many seconds are in 1 day?

1 day equals 86400 seconds.

How do I convert days to seconds?

Multiply the day value by 86400. So x d × 86400 = the equivalent in s.

What is 5 days in seconds?

5 days equals 432000 seconds.

What is 10 days in seconds?

10 days equals 864000 seconds.

What is 100 days in seconds?

100 days equals 8640000 seconds.

How do I convert back from seconds to days?

Multiply the second value by 1.1574 × 10^−5. For example, 1 s = 1.1574 × 10^−5 d.

Is the day bigger than the second?

Yes. 1 day is larger than 1 second — specifically 86400 times larger.

Are these conversion factors exact?

The factor is derived directly from the SI definitions of day and second; the displayed value is rounded for readability, and the browser computes using IEEE 754 double-precision arithmetic.

About the day and the second

Sources

• NIST Special Publication 811 — Guide for the Use of the International System of Units (SI)
• BIPM — SI Brochure (9th edition)
• Reverse: s to d
• All time converters