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555 Astable Timing Calculator

Online 555 astable timing calculator. Standard two-resistor astable with ideal one-third and two-thirds thresholds.

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555 astable timing calculator online

Use 555 astable timing calculator online for ra ohm, rb ohm, capacitance F. Standard two-resistor astable with ideal one-third and two-thirds thresholds. Ideal nominal component model. Verify topology, operating range, tolerances and ratings against the actual component datasheet.

How to use it

Enter ra ohm. Set rb ohm, capacitance F. Select Calculate and check the labeled output. Copy or download the JSON result.

Options and example settings

OptionChoices / valueExample default
ra ohmMain input. Positive values. 1000
rb ohmOption. Positive values. 10000
capacitance FOption. Positive values. 0.000001

Calculation method

frequency_Hz = 1/(ln(2)*(ra_ohm+2*rb_ohm)*capacitance_F); high_duty_pct = 100*(ra_ohm+rb_ohm)/(ra_ohm+2*rb_ohm) (^ means exponentiation; trig functions ending in d use degrees).

Worked examples

Apply 555 astable timing calculator to the case below, keeping the displayed units and assumptions. Standard two-resistor astable with ideal one-third and two-thirds thresholds.

555 Astable Timing Calculator — worked case

Settings: rb ohm: 10000; capacitance F: 0.000001

Input:

1000

Calculated result for these inputs:

Output:

{
  "frequency_Hz": 68.69976385185541,
  "high_duty_pct": 52.38095238095238
}

Choose the right tool

Match the topology before entering values: series and parallel networks, inverting and noninverting stages, and buck and boost converters use different equations. Component ratings, parasitics, protection and measured conditions require separate review.

Limitations and common mistakes

  • Standard two-resistor astable with ideal one-third and two-thirds thresholds. Ideal nominal component model. Verify topology, operating range, tolerances and ratings against the actual component datasheet.
  • Use the displayed unit in every field. Ratios and percentages are different inputs; percent fields use values such as 25 rather than 0.25.

Frequently asked questions

How can I use 555 astable timing calculator online?

Enter ra ohm. Set rb ohm, capacitance F. Select Calculate and check the labeled output. Copy or download the JSON result.

Technical references

Where is my input processed?

The bundled tool processes input in your browser. It does not upload tool input to a conversion service. Other site plugins, analytics, advertising and browser extensions may have separate behavior.

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