Oscilloscope Selection Calculator

Bandwidth and sample rate from signal requirements.

R1 - Timing Resistor (Ω)

R2 - Timing Resistor (Ω)

Timing Capacitor (nF)

Tab to move between fields

Frequency (Hz)

138.75

Duty Cycle (%)

54.81

Frequency (kHz)0.14

Period (ms)7.21

High Time (ms)3.95

Low Time (ms)3.26

Avg Timing Current (mA)0.05

Period (µs)7,207.2

Nearest NoteC#3

How to Use This Calculator

Enter the timing resistor values R1 and R2 (Ω) and timing capacitor value (nF) for your 555 circuit.
Review the calculated output frequency (Hz and kHz), duty cycle (%), and period (ms).
Adjust R1, R2, or C to tune frequency and duty cycle to your target values.
Use the high-time and low-time outputs to verify timing against your circuit requirements.

How the result changes with Timing Capacitor (nF)

R1 - Timing Resistor (Ω): R1 connects between Vcc and the discharge pin (pin 7). Min 1kΩ recommended.
R2 - Timing Resistor (Ω): R2 connects between discharge (pin 7) and threshold/trigger (pins 6/2).
Timing Capacitor (nF): Timing capacitor in nanofarads (1 µF = 1000 nF). Connects from threshold to ground.

Frequency (Hz): Output oscillation frequency: f = 1.44 / ((R1 + 2R2) × C).
Frequency (kHz): Frequency in kilohertz for higher-speed applications.
Duty Cycle (%): Percentage of time output is HIGH. Always >50% in standard astable mode.
Period (ms): Total cycle time (t_high + t_low).
High Time (ms): Time output is HIGH: 0.693 × (R1 + R2) × C.
Low Time (ms): Time output is LOW: 0.693 × R2 × C.
Avg Timing Current (mA): Approximate average current through timing resistors (at 5V Vcc).
Period (µs): Period in microseconds for high-frequency applications.

Identify Input Parameters
R1 - Timing Resistor (Ω) = 10000, R2 - Timing Resistor (Ω) = 47000, Timing Capacitor (nF) = 100 = 3 input(s) provided
Calculate Frequency
138.75 = 138.75
Calculate Duty Cycle
54.81 = 54.81
Calculate Frequency
Frequency = frequency / 1000
0.1388 = 0.1388
Calculate Period
Period = period * 1000
7.2072 = 7.2072