555 astable — common cases, pre-computed
Output frequency for the most common R1 / R2 / C combinations in 555 astable (free-running) mode. Need different values? Open the interactive calculator.
- R1=1kΩ · R2=1kΩ · C=100nF 4.809 kHz
- R1=1kΩ · R2=10kΩ · C=100nF 686.998 Hz
- R1=1kΩ · R2=10kΩ · C=1µF 68.7 Hz
- R1=10kΩ · R2=10kΩ · C=1µF 48.09 Hz
- R1=10kΩ · R2=68kΩ · C=10µF 0.988 Hz
- R1=1kΩ · R2=1kΩ · C=1nF 480.898 kHz
- R1=4.7kΩ · R2=4.7kΩ · C=100nF 1.023 kHz
- R1=10kΩ · R2=100kΩ · C=1µF 6.87 Hz
Ideal textbook values — capacitor tolerance and leakage shift the real frequency. Trim by measurement when timing matters.