IC 555 Astable Timer Calculator

IC 555 Astable Timer

A common integrated circuit used in electronics to generate continuous square wave output signals is the IC 555 astable timer. It is a multipurpose circuit.
It functions in an astable mode, which means that internal timing components allow it to generate oscillations on its own without the need for external triggering.

The IC 555 astable timer’s main function is to supply an oscillating signal that is both stable and controllable for a range of timing and pulse generation applications.
It is appropriate for a variety of electronic projects because it provides an easy and dependable way to generate continuous square wave signals with adjustable frequency and duty cycle.

Understanding IC 555 Astable TImer:

Astable Mode:

In astable mode, the 555 timer IC functions as an oscillator, generating a square wave output whose frequency can be tuned by altering the values of two resistors (R1 and R2) and a capacitor (C). The output frequency can be determined using the following formula:

Key Components:

R1 and R2

These two resistors, R1 and R2, are pivotal in determining the output frequency of the 555 timer. The ratio between R1 and R2 plays a crucial role in shaping the duty cycle of the output waveform.

C: This capacitor is responsible for storing the charge and discharge cycles within the 555 timer. The value of C directly impacts both the output frequency and the duty cycle of the waveform.

VCC: This voltage denotes the power supply voltage for the 555 timer, typically ranging between 4.5V and 16V for most applications.

The astable mode of the 555 timer IC offers several advantages, such as:

High frequency stability

Low power consumption

Simple circuit design

Wide range of output frequencies


  • Pulse Generation
  • LED Flashers
  • Tone Generation
  • Timing Circuits
  • Waveform Generators


To summarize, the astable mode of the 555 timer IC stands out as a versatile and extensively employed configuration capable of generating a continuous stream of pulses or a square wave. Its flexibility lies in the ability to adjust the output frequency through manipulation of two resistors and a capacitor, rendering it a favored option across various electronic applications.

With the resistance and capacitance values provided, this online calculator helps determine the time-out value (delay) of the IC 555 timer in an astable mode circuit. It lets you figure out exactly what time parameters your circuit layout needs.

Note : Don’t end with comma ( , )



\[T1 = 0.7(R1+R2)*C \\T2 = 0.7*R1*C \\T = 0.7(R1+R2)*C \\F = 1.45 / ((R1+2R2)*C) \\D =0.1-((0.1*R2) / (R1+(2R2)));\]


  • T1 = High Period
  • T2 = Low Period
  • T = Total Period
  • F = Frequency
  • D = Duty

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