555 Timer Frequency Calculator
NE555 Online Frequency Calculator — enter component parameters such as resistors and capacitors to instantly calculate output frequency, duty cycle, and high/low level times.
Find outputs from component values
Enter R1, R2, and C to calculate T₁, T₂, the total period, frequency, and duty cycle (duty cycle ≥ 50%)
Formula
Find resistor values from target outputs
Enter the target frequency, duty cycle, and capacitance to solve for the required R1 and R2 values (duty cycle ≤ 50%)
Solve from target outputs or component values
Enter any known combination of parameters (frequency + duty cycle, or R1 + R2 + C) and automatically solve for the remaining unknowns (duty cycle ≥ 50%)
— Or enter component values —
How to use
- Method 1:Enter frequency + duty cycle (+ optional capacitance), and R1, R2, C are calculated automatically
- Method 2:Enter frequency + duty cycle (without capacitance); a suitable capacitor is selected automatically and the resistors are calculated
- Method 3:Enter R1, R2, C, and the frequency and duty cycle are calculated automatically
When the duty cycle is < 50%, "Inverted output" is checked automatically and the duty cycle is converted to 1 − Duty for calculation.
About the NE555 IC
The NE555 is a classic timer IC widely used for pulse generation, timing control, and oscillator circuits. With only a few external resistors and capacitors, it supports multiple operating modes.
Astable mode:Outputs a continuous square wave whose frequency and duty cycle are set by R1, R2, and C. Commonly used for LED flashing, buzzer drive, and clock sources.
Key formulas: