how long is a jiffy

June 27, 2026

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.