PWM Duty Cycle Calculator

Enter the high time, period, and supply voltage to calculate duty cycle, average voltage, RMS voltage, PWM frequency, and low time.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Input the high time (on-duration)
Enter the duration, in milliseconds, that the PWM signal is in its high (on) state within one complete cycle.
2
Specify the total period
Provide the total duration, in milliseconds, of one full PWM cycle (high time + low time).
3
Enter the supply voltage
Input the voltage level, in Volts, that the PWM signal reaches during its high state.
4
Review your PWM signal characteristics
The calculator will display the duty cycle, average voltage, RMS voltage, frequency, and low time, offering a complete overview of the PWM signal.

Example Calculation

An engineer is analyzing a PWM signal with a 2 ms high time, a 10 ms total period, and a 5 V supply voltage.

High Time (ms)

Period (ms)

Supply Voltage (V)

Results

20.00%

Tips

Match PWM Frequency to Application

For motor control, use frequencies above 20 kHz to avoid audible noise. For LED dimming, frequencies above 100 Hz are often sufficient to prevent flicker.

Consider MOSFET Gate Drive

When using PWM with MOSFETs, ensure your gate driver can supply sufficient current to quickly charge/discharge the gate capacitance, especially at high frequencies, to minimize switching losses.

Filter for Analog Equivalence

To convert a PWM signal into a stable analog voltage, use a low-pass filter (RC or LC). The filter's cutoff frequency should be significantly below the PWM frequency for effective smoothing.

Mastering Signal Control: The PWM Duty Cycle Calculator

Pulse Width Modulation (PWM) is a fundamental technique in modern electronics, enabling efficient control of power delivery to various loads. The PWM Duty Cycle Calculator provides essential metrics for analyzing these signals, including the duty cycle, average voltage, RMS voltage, and frequency. For a signal with a 2 ms high time, a 10 ms period, and a 5 V supply, the calculated duty cycle is 20.00%. This tool is invaluable for electrical engineers designing everything from motor controllers to LED dimmers in 2025.

Applications of Pulse Width Modulation in Electronics

Pulse Width Modulation (PWM) is a versatile technique with widespread applications across various electronic systems due to its high efficiency and precise control capabilities. In motor control, PWM varies the speed and torque of DC motors by adjusting the average voltage supplied, allowing for smooth acceleration and deceleration while minimizing energy waste. For LED dimming, PWM rapidly switches LEDs on and off, with the human eye perceiving changes in brightness based on the duty cycle, without altering the LED's color temperature. It's also critical in power regulation, such as in DC-DC converters, where it efficiently steps voltages up or down. Furthermore, in audio amplification, Class D amplifiers use PWM to convert analog audio signals into a series of pulses, achieving high efficiency by minimizing power dissipation in the switching components.

Unpacking the PWM Signal Characteristics

The PWM Duty Cycle Calculator uses fundamental electrical engineering principles to derive key characteristics of a pulse-width modulated signal. The duty cycle defines the proportion of "on" time, which then directly influences the average voltage and effective power delivered.

duty cycle (%) = (high time (ms) / period (ms)) × 100
low time (ms) = period (ms) - high time (ms)
average voltage (V) = (duty cycle (%) × supply voltage (V)) / 100
frequency (Hz) = 1000 / period (ms)
RMS voltage (V) = supply voltage (V) × sqrt(duty cycle (%) / 100)

For a high time of 2 ms, period of 10 ms, and supply voltage of 5 V: Duty Cycle = (2 / 10) × 100 = 20% Low Time = 10 - 2 = 8 ms Average Voltage = (20 × 5) / 100 = 1 V Frequency = 1000 / 10 = 100 Hz RMS Voltage = 5 × sqrt(20 / 100) = 5 × sqrt(0.2) ≈ 2.236 V.

💡 PWM is often used for motor control, where understanding torque is crucial. Our Induction Motor Torque Calculator can help you assess the mechanical output of such systems.

Analyzing a PWM Signal for a DC Motor Driver

Imagine an electrical engineer designing a driver circuit for a small DC motor. They are using a PWM signal generated with a 2 ms high time and a total period of 10 ms, powered by a 5 V supply.

Calculate Duty Cycle: (2 ms high time / 10 ms period) × 100 = 20%. This means the signal is "on" for 20% of each cycle.
Determine Low Time: 10 ms period - 2 ms high time = 8 ms. The signal is "off" for 8 ms.
Find Average Voltage: (20% duty cycle × 5 V supply) / 100 = 1 V. The motor will effectively see an average of 1 V.
Compute Frequency: 1000 ms/s / 10 ms period = 100 Hz. This is the switching frequency.
Calculate RMS Voltage: 5 V × sqrt(20% / 100) = 5 V × sqrt(0.2) ≈ 2.236 V. This represents the effective voltage in terms of power delivery.

These values confirm the signal's characteristics, informing the engineer about the motor's expected performance.

💡 When integrating PWM signals into complex circuits, proper component selection is key. Our Impedance Matching Calculator can help ensure efficient power transfer between stages.

Regulatory or Standards Context for PWM Frequency and EMI

Pulse Width Modulation (PWM) signals, by their very nature of rapid switching, can generate electromagnetic interference (EMI) that must be managed to comply with regulatory standards. In the United States, the Federal Communications Commission (FCC) sets limits on conducted and radiated emissions for electronic devices, categorized by Class A (commercial/industrial) and Class B (residential). For example, devices using PWM in power supplies must ensure their switching frequencies and harmonics do not exceed specified limits in the 30 MHz to 1 GHz range. The International Electrotechnical Commission (IEC) and European Union's CE marking also impose similar standards, such as IEC 61000 series, for electromagnetic compatibility (EMC). Designers often employ techniques like spread spectrum clocking, shielding, and filtering (e.g., common-mode chokes) to mitigate EMI and ensure compliance, especially when PWM frequencies operate in sensitive ranges, like those used in automotive or medical applications.

Frequently Asked Questions

What is PWM duty cycle?

PWM (Pulse Width Modulation) duty cycle is the ratio of the pulse's 'on' time (high time) to the total period of the pulse, expressed as a percentage. It represents the proportion of time the signal is active within one complete cycle, and by varying this percentage, the effective average power delivered to a load can be controlled, from 0% (always off) to 100% (always on).

How does PWM control power?

PWM controls power by rapidly switching a signal between on and off states, effectively varying the average voltage or current supplied to a load over time. By increasing the duty cycle (more 'on' time), more power is delivered, while decreasing it (more 'off' time) reduces power. This method is highly efficient as the switching components are either fully on or fully off, minimizing resistive losses.

What is the relationship between PWM frequency and period?

PWM frequency and period are inversely related: Frequency (Hz) = 1 / Period (seconds). If the period is given in milliseconds, then Frequency (Hz) = 1000 / Period (ms). For example, a 10 ms period corresponds to a 100 Hz frequency, meaning the signal completes 100 cycles per second, determining the speed of switching.

What is RMS voltage in PWM?

The RMS (Root Mean Square) voltage of a PWM signal represents its effective DC equivalent voltage in terms of power delivery to a resistive load. It is calculated as the supply voltage multiplied by the square root of the duty cycle (expressed as a decimal). While the average voltage determines the DC equivalent, RMS voltage is more relevant for calculating the actual power dissipated by a load.