555 Astable Calculator

Summary

A 555 timer IC wired in astable mode produces a continuous square wave whose frequency and duty cycle are determined by two resistors (R1 and R2) and a timing capacitor (C). This calculator applies the standard datasheet equations to give you frequency in Hz or kHz, total period in ms or µs, high time (charge), low time (discharge), and duty cycle percentage — all updated instantly as you adjust component values.

How it works

1. Enter R1 and R2 values and select the unit (Ω or kΩ) for each.
2. Enter the capacitor value and select the unit (µF, nF, or pF).
3. Click Calculate to see frequency, period, duty cycle, t_high, and t_low.
4. Switch units at any time and recalculate — values are converted automatically.
5. Use Reset to clear all fields and start a new design.

Use cases

• Design a square-wave clock signal for a microcontroller prototype.
• Set the blink rate of an LED flasher at a specific frequency.
• Size R1, R2, and C to hit a target duty cycle for a PWM application.
• Verify component values read from a 555 astable schematic.
• Teach or learn astable timer theory with live numeric feedback.

Frequently Asked Questions