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555 Timer Monostable Calculator

Estimate the output pulse duration of a standard 555 one-shot timer.

Ideal component relationshipsUnits and assumptions explained below
Circuit workbench
Circuit workbench

Keep RMS, peak and DC values distinct.

See the method

Enter circuit values

Runs on your device

Your circuit result

Your result

Let’s calculate.

Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter timing resistance, timing capacitance.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

The method, explained

Pulse time = ln(3)RC, using the ideal two-thirds-supply threshold.

A WORKED EXAMPLE

Using timing resistance = 100 kΩ, timing capacitance = 10 µF, the result is 1.09861229 s. Change these example inputs to match your task; use the method above to check each step.

Understanding your result

A single externally triggered pulse is assumed. Leakage, trigger duration and tolerances can change the observed pulse.

What to keep in mind

A single externally triggered pulse is assumed. Leakage, trigger duration and tolerances can change the observed pulse. Ideal-component calculation for study and estimation. It does not select safe wiring, protective devices or component ratings for an installation.

Common questions

How do I use this 555 timer monostable calculator?

Estimate the output pulse duration of a standard 555 one-shot timer. Enter timing resistance in kΩ, timing capacitance in µF. The starting example is editable; use values for the same system or project.

Which assumptions affect this result?

A single externally triggered pulse is assumed. Leakage, trigger duration and tolerances can change the observed pulse.

Methodology maintained by ClarityKit. How these tools are built and checked.