555 Monostable Calculator
Enter R and C values to instantly compute the output pulse width for a 555 timer in monostable (one-shot) mode.
Component Values
Results
Pulse Width (T)
—
R × C (time constant)
—
Equivalent Frequency
—
Output Waveform (one-shot)
Trigger
T
Diagram is proportional to pulse width relative to the full timeline shown.
Formula
T = 1.1 × R × C
Monostable Formulas
T = 1.1 × R × C
T ≈ -ln(1/3) × R × C
R (given T, C) = T / (1.1 × C)
C (given T, R) = T / (1.1 × R)
T is the output pulse width in seconds, R in ohms, C in farads. The constant 1.1 comes from –ln(1 – 2/3) = ln(3) ≈ 1.0986.
Summary
Enter R and C values to instantly compute the output pulse width for a 555 timer in monostable (one-shot) mode.
How it works
- Enter the timing resistor (R) value and select the unit (Ω or kΩ).
- Enter the timing capacitor (C) value and select the unit (µF, nF, or pF).
- Click Calculate to see the output pulse width T = 1.1 × R × C.
- The result is shown in the most readable time unit (ns, µs, ms, or s).
- Use Reset to clear all fields and start a new design.
Use cases
- Set a fixed debounce delay for a pushbutton input.
- Generate a precise one-shot pulse to latch a downstream circuit.
- Size R and C to produce a specific time delay from a trigger signal.
- Verify timing component values read from a 555 monostable schematic.
- Prototype a missing-pulse detector by comparing measured pulse width.
- Teach or learn monostable 555 timer theory with live numeric feedback.
Frequently Asked Questions
Last updated: 2026-07-01 ·
Reviewed by Nham Vu