Timer 555 Calculator

Here the widespread timer NE555 as an astable multivibrator. The circuit produces a square wave signal. Frequency and duty cycle are both controlled with two external resistors and one capacitor. The circuit can be used as an audio signal oscillator, clock generator or timer circuit for switching times in the range from a few microseconds up to several hours.
Put in the values for R1, R2 and C1 into the white fields to calculate the frequency and the duty cycle.

R1 [kΩ]:
R2 [kΩ]:
C [µF]:
Frequency [Hz]:
Period [s]:
thigh [s]:
tlow [s]:
Duty cycle: