Whether you’re building a flickering LED or a precision pulse generator, this 555 Timer Calculator simplifies the math. Just enter your resistor and capacitor values to determine the exact timing characteristics of your circuit.
Choose Your Configuration
The 555 timer is famously versatile, operating primarily in two distinct modes:
- Astable Mode (Continuous Pulse): Use this to create a “free-running” oscillator. The calculator will provide the frequency, duty cycle, and the specific Time High vs. Time Low intervals.
- Monostable Mode (One-Shot): Use this for timers and delay circuits. The calculator will determine the precise output pulse duration triggered by an external signal.
Understanding the Physics
The timing for these modes is governed by the RC time constant, where the relationship between resistance (R) and capacitance (C) dictates the behavior. For example, in Monostable mode, the pulse width (T) is calculated as:
T = 1.1 x R x C
Component Values
Timing resistor
Discharge resistor
Timing capacitor
Results
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Enter component values and pressCalculate to see results
Formulas
Time High (TH)
0.693 × (R1 + R2) × C1
Time Low (TL)
0.693 × R2 × C1
Period (T)
TH + TL
Frequency (f)
1.44 / ((R1 + 2×R2) × C1)
Duty Cycle
(R1 + R2) / (R1 + 2×R2) × 100%