IC 555 Timer Calculator

Enter value and click on calculate. Result will be displayed.

Tp = 0.693 × (Ra + Rb) × C
Tn = 0.693 × Rb × C
Frequency = 1.44 / [(Ra + Rb + Rb) × C]

Enter your values:

Resistance Ra:
K Ohms
Resistance Rb:
K Ohms


Positive Time Interval Tp:
Negative Time Interval Tn:
What is the 555 IC?

The 555 chip is a widely used integrated circuit that has kept the tempo in innumerable projects since the 70s. It can operate in various modes:

Monostable mode, where a single state is destabilized for a given time;

Bistable mode, where the chip remains in one of two stable states until prompted to change; and

Astable mode, in which the output of the 555 oscillates between a "high" state and a "low" state in the shape of a rectangular wave.

The chip's applications are varied: you can use it to create timers, pulses, or delays in your circuit in the monostable mode, flip-flops circuits (not the sandals) in the bistable mode, and – most commonly – as an oscillator in the astable mode.

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