Planck time
| Value | 1 tP (5.391247 × 10⁻⁴⁴ s) |
| Status | Measured: ± 1.1 × 10⁻⁶ tP (1.1 × 10⁻⁶ relative), standard uncertainty |
| Source | CODATA 2022 (derived from ħ, c and G; uncertainty inherited from G) |
| Categories | Universal & AtomicQuantum |
| Unit | Value |
|---|---|
| Planck time | 1 tP |
21 more time units
| attosecond | 5.3912470e-26 as |
| femtosecond | 5.3912470e-29 fs |
| picosecond | 5.3912470e-32 ps |
| nanosecond | 5.3912470e-35 ns |
| shake | 5.3912470e-36 shake |
| microsecond | 5.3912470e-38 µs |
| millisecond | 5.3912470e-41 ms |
| second | 5.3912470e-44 s |
| minute | 8.9854117e-46 min |
| hour | 1.4975686e-47 h |
| sidereal day | 6.2569534e-49 sd |
| day | 6.2398692e-49 d |
| week | 8.9140989e-50 wk |
| fortnight | 4.4570494e-50 fn |
| month | 2.0501018e-50 mo |
| year | 1.7083831e-51 yr |
| decade | 1.7083831e-52 dec |
| century | 1.7083831e-53 cent |
| millennium | 1.7083831e-54 mil |
| megayear | 1.7083831e-57 Myr |
| eon | 1.7083831e-60 eon |
Learning zone
The Planck time is simply l_P/c, and it is the shortest interval that has any operational meaning in current theory: measuring a shorter one would require an energy so concentrated that it would collapse into a black hole. For scale, the shortest pulses laboratories can make are attoseconds, 10⁻¹⁸ s: still 10²⁶ Planck times long.
Cosmology uses it as a boundary marker. "The Planck epoch" is the first 10⁻⁴³ s after the Big Bang, before which general relativity and quantum field theory give contradictory answers and the honest statement is that nobody knows. Everything cosmologists do describe (inflation at around 10⁻³⁶ s, quark-gluon plasma at microseconds, nucleosynthesis at minutes) happens comfortably afterwards. Note that "time began at t_P" is a statement about the limits of our theories, not a discovery about the universe.
Cite this page
formula.expert. (2026, October 16). Planck time. https://formula.expert/constants/planck-time