A “jiffy” actually does have several precise meanings, depending on the field.

Quick Scoop: So… how long is a jiffy?

In everyday speech, “in a jiffy” just means “very soon” or “in a moment,” with no strict timing at all. But scientists and engineers have turned jiffy into a real unit of time in a few different ways:

1. In physics (very, very tiny)

  • In some physics contexts, a jiffy is the time it takes light to travel one fermi (one femtometre, 10−1510^{-15}10−15 m), roughly the size of a nucleon.
  • That works out to about 3×10−243\times 10^{-24}3×10−24 seconds – incredibly shorter than anything you could feel or notice.

2. In electricity / power systems

  • In AC power engineering, a jiffy is sometimes used for “one cycle” of the mains current.
  • In the UK and most of Europe (50 Hz), that’s 1/501/501/50 of a second = 0.02 seconds.
  • In places with 60 Hz mains, that would correspond to roughly 1/60 of a second ≈ 0.0167 seconds, when people use the term this way.

3. In computing

  • In computing, “jiffy” is used informally for the duration of one tick of the system timer.
  • That tick length depends on the operating system, but it’s often on the order of a few milliseconds (for example, about 10 ms in some systems), which is 0.01 seconds.

4. Older scientific proposal

  • Physicist Gilbert N. Lewis once proposed a jiffy as the time it takes light to travel one centimeter, about 33.3564 picoseconds (3.3×10−113.3\times 10^{-11}3.3×10−11 seconds).
  • This was another attempt to tie the word to a specific distance at the speed of light.

5. Everyday language

  • When people say “I’ll be back in a jiffy,” they just mean “really soon,” not any of the precise definitions above.
  • So in daily life, a jiffy is a fuzzy, friendly way to say “a very short time,” while in science it can range from around 10−2410^{-24}10−24 seconds up to a hundredth of a second, depending on the context.

TL;DR:

  • Casual speech: “a brief moment.”
  • Physics: about 3×10−243\times 10^{-24}3×10−24 seconds (light crossing a fermi).
  • Power systems: one AC cycle (e.g., 1/50 second = 0.02 s).
  • Computing: one system “tick,” often around 0.01 s.

Information gathered from public forums or data available on the internet and portrayed here.