555 Timer — Monostable

How to use this calculator

In monostable (one-shot) mode the 555 produces a single fixed-width pulse each time it is triggered. The pulse width is t = 1.1 · R · C. Enter R and C and the pulse duration (and the equivalent 1-pulse-per-second frequency) appears live.

What it means in a real circuit

This is the classic "hold the LED on for a set time" or "debounce a button" circuit. For R = 100 kΩ and C = 100 µF the pulse is 1.1 × 100,000 × 0.0001 = 11 seconds. Use it for timers, delay circuits, and turning something on for a defined period from a momentary trigger. The output is high for the pulse width, then returns low until the next trigger.