Convert Days to Seconds
1 day (d) equals 86400 seconds (s).
Converting a list? Use the bulk day to second converter to paste a column from Excel.
How to Convert Day to Second
- 1 d = 86400 s
- 1 s = 0.00001157407407 d
- Example: convert 15 d to s: 15 d = 15 × 86400 s = 1296000 s
Formula
s = d × 86400
Derivation from SI units:
- 1 d = 24 h = 86 400 s
- SI base unit: 9 192 631 770 periods of the caesium-133 hyperfine transition
Both units are defined exactly, so the factor is exact. Day definition: day; Second definition: second.
Worked examples
- 1 d equals 86400 s.
1 d × 86400 = 86400 s - 365 d, a common year, is 31536000 s.
365 d × 86400 = 31536000 s
Day to Second conversion table
| Days (d) | Seconds (s) |
|---|---|
| 0.5 d | 43200 s |
| 1 d | 86400 s |
| 2 d | 172800 s |
| 3 d | 259200 s |
| 5 d | 432000 s |
| 7 d | 604800 s |
| 10 d | 864000 s |
| 14 d | 1209600 s |
| 15 d | 1296000 s |
| 21 d | 1814400 s |
| 28 d | 2419200 s |
| 30 d | 2592000 s |
| 31 d | 2678400 s |
| 45 d | 3888000 s |
| 60 d | 5184000 s |
| 90 d | 7776000 s |
| 100 d | 8640000 s |
| 180 d | 15552000 s |
| 365 d | 31536000 s |
| 366 d | 31622400 s |
| 1000 d | 86400000 s |
Where it's used
Daily totals such as m³/day are converted to per-second rates by dividing by 86 400 s.
Day to other time units
| Conversion | 1 d equals |
|---|---|
| day to millisecond | 86400000 ms |
| day to second | 86400 s |
| day to minute | 1440 min |
| day to hour | 24 h |
Frequently asked questions
How many seconds are in a year?
A 365-day year has 31536000 s; a 366-day leap year has 31622400 s.
How many seconds are in 1 day?
1 d = 86400 s.
How do I convert days to seconds?
Multiply the value in d by 86400. For example, 15 d × 86400 = 1296000 s.
Is the d to s conversion exact?
Yes. Both units are defined exactly, and 1 d is exactly 86400 s.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 8, non-SI units accepted for use with the SI.
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Section 2.3.1, base unit definitions.
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Days to Seconds. Retrieved October 17, 2026, from https://scientificconverters.com/time/days-to-seconds/
IEEE
Scientific Converters, "Convert Days to Seconds," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/time/days-to-seconds/