RC Debounce Calculator

Calculate RC time constant, switch debounce delay, resistor value, capacitor value, cutoff frequency and Schmitt-trigger threshold time for push buttons and mechanical switches.

⚡ Maker Rule: A mechanical button can bounce for a few milliseconds. An RC debounce circuit slows the input edge so your microcontroller sees one clean transition. Use this with the Pull-up Resistor Calculator, ADC Resolution Calculator, PWM Duty Cycle Voltage Calculator and Voltage Divider Calculator.

⏱️ RC Debounce — Noisy Switch to Clean Logic Input

Resistor Value

Capacitor Value

Supply / Logic Voltage

Logic Threshold

Expected Switch Bounce

Input Type

One time constant τ = R × C. The node reaches about 63.2% after 1τ, 86.5% after 2τ, and 95% after 3τ.

Presets:button 10msnoisy switchfast input

Target Debounce Time

Known Component

Known Resistor

Known Capacitor

Threshold Target

This solves R or C for a desired time to reach a selected input threshold.

Resistor Value

Capacitor Value

VCC

Rising Threshold VIH

Falling Threshold VIL

Schmitt-trigger inputs are better for RC debounce because they have separate rising and falling thresholds.

📐 Formula Reference

RC Time Constant

τ = R × C

Charging Voltage

V(t) = Vcc × (1 − e^(−t/RC))

Threshold Time

t = −RC × ln(1 − Vth/Vcc)

Cutoff Frequency

fc = 1 ÷ (2πRC)

📋 Quick Reference

Typical Bounce Time

Tact button5–10ms

Toggle switch10–20ms

Relay contact5–15ms

Common Values

10k + 100nF1ms

10k + 1µF10ms

100k + 100nF10ms

Best Practice

Use Schmitt inputclean

Avoid huge Rnoise

Add software debouncerobust

📚 Engineering Notes

RC slows the edgeA capacitor prevents the input from instantly following switch bounce, reducing false triggers.

Schmitt trigger input is recommendedSlow RC edges can confuse normal logic inputs. A Schmitt input gives cleaner switching thresholds.

Hardware and software can work togetherSmall RC filtering plus software debounce is often the most reliable solution.

Pull-up value mattersUse the Pull-up Resistor Calculator to check input current, rise time and noise margin.

What is an RC Debounce Calculator?

An RC debounce calculator helps choose resistor and capacitor values for debouncing mechanical switches and push buttons. It calculates RC time constant, threshold delay and cutoff frequency.

How RC switch debounce works

A resistor and capacitor form a low-pass filter. When the switch bounces, the capacitor voltage changes slowly, so short bounce pulses are filtered before reaching the logic input.

Choosing RC debounce values

For many push buttons, a debounce time around 5–20ms is a practical starting point. Common values include 10kΩ with 1µF or 100kΩ with 100nF, depending on input current and noise environment.

Important limitation

This calculator gives ideal RC math. Real switch debounce depends on contact type, pull-up configuration, input leakage, Schmitt trigger thresholds, PCB noise, cable length and software debounce strategy.

❓ Frequently Asked Questions

Switch bounce is the rapid make-break action that happens when a mechanical contact opens or closes. It can create multiple false pulses.

Both can work. RC debounce helps clean the signal electrically, while software debounce gives flexibility. Many robust designs use both.

A Schmitt trigger handles slow RC edges better because it has clean switching thresholds and hysteresis.