Day (d)
The day (d) is exactly 86 400 seconds (24 hours). Calendar days that contain a leap second are not covered by this fixed conversion.
Symbol: d
Quantity: time (duration)
SI relation: 1 d = 86400 s (exact)
Derivation: 1 d = 24 h = 86 400 s
Exact: yes, by definition
Typical uses
- Incubation, curing and stability-test durations
- Daily flow and production totals
- Half-lives and retention periods
Convert days to other units
| Conversion | 1 d equals | Reverse |
|---|---|---|
| day to second | 86400 s | second to day |
| day to minute | 1440 min | minute to day |
| day to hour | 24 h | hour to day |
| day to millisecond | 86400000 ms | millisecond to day |
Open the Time Converter to convert any value between all units.
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.
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). Day (d). Retrieved October 17, 2026, from https://scientificconverters.com/units/day/
IEEE
Scientific Converters, "Day (d)," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/units/day/