555 Timer - Frequency and Duty Cycle Calculator

Enter values for R1, R2, and C and press the calculate button to solve for positive time interval (T1) and negative time interval (T2). For example, a 10KW resistor (R1) and 100KW (R2) and 0.1 uF capacitor will produce output time intervals of 7.62 mS positive (T1) and 6.93 mS negative (T2). The frequency will be about 70 Hz. R1 should be greater than 1KW and C should be greater than .0005 uF.

Positive Time Interval (T1) = 0.693 * (R1+R2) * C
Negative Time Interval (T2) = 0.693 * R2 * C
Frequency = 1.44 / ( (R1+2*R2) * C)

Maintained by John Loomis, last updated 8 Sept 2007

R1 (K Ohms)	R2 (K Ohms)	C (Microfarads)

T1 (Milliseconds)	T2 (Milliseconds)	Frequency (Kilohertz)