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555 Astable Calculator

Calculate 555 astable period, capacitance or timing resistors, with frequency, on-time, off-time and duty-cycle results.

  • Type: Electronics calculator
  • Formula: T ≈ 0.693 × (R1 + 2R2) × C
  • Units: Engineering notation
  • Runs locally in your browser

555 astable timing network

Select the value to calculate, then enter the remaining values.

Enter values and select Calculate.

Frequency—
On time—
Off time—
Duty cycle—

Using the result

The calculator uses the ideal textbook relationship shown above. Real components have tolerance and practical circuits can introduce loading, leakage, bandwidth and other effects, so choose real component values with suitable margin for your design.

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