Boost Converter Duty Cycle Calculator
A boost converter steps a lower input voltage up to a higher regulated output by storing energy in an inductor and releasing it in series with the source. The duty cycle, the fraction of each switching period the switch is on, sets how much the voltage is raised. This calculator finds the required duty cycle from the input and output voltages, with an optional efficiency factor, and reports the on-time and off-time when you add a switching frequency. The ideal continuous-conduction relationship is D = 1 - (Vin / Vout), and it is the starting point for any step-up regulator design.
Boost duty cycle formula
ideal duty cycle D = 1 - (Vin / Vout)
with losses D = 1 - (Vin * efficiency) / Vout
period T = 1 / switching frequency
on-time = D * T, off-time = (1 - D) * T
Efficiency is a fraction between 0 and 1. The on-time and off-time use the switching frequency entered in kilohertz, converted internally and shown in microseconds.
Design notes
- A boost duty cycle is between 0 and 1; the output is always above the input.
- Lower efficiency raises the required duty cycle.
- The relationship assumes continuous conduction mode.
- On-time plus off-time equals one switching period.
- Output voltage must exceed the input voltage for a boost topology.
Boost converter: frequently asked questions
What is the boost converter duty cycle formula?
For an ideal step-up (boost) converter in continuous conduction, the duty cycle is D = 1 - (Vin / Vout). With efficiency to account for losses, D = 1 - (Vin * efficiency) / Vout. The duty cycle is the fraction of each period the switch is on, storing energy in the inductor.
Why does a boost converter step voltage up?
During the on-time the inductor stores energy from the input; during the off-time that energy adds to the input and is delivered to the output through the diode. Because the inductor's stored energy adds to the source, the output voltage is higher than the input.
How does efficiency change the duty cycle?
Losses mean the converter must work a little harder, raising the duty cycle. Multiplying the input by the efficiency in the formula increases D. Lower efficiency therefore demands a higher duty cycle to reach the same output voltage.
Can a boost converter output a lower voltage than the input?
No. A boost topology only steps up, so the output must be higher than the input and the duty cycle stays between 0 and 1. If you need a lower output, use a buck converter or a buck-boost topology instead.
What switching on-time results from the duty cycle?
With switching frequency f, the period is 1 / f and the switch on-time is D / f. For instance, a 0.6 duty cycle at 100 kHz gives a 6 microsecond on-time within a 10 microsecond period.
Official sources
- NIST: SI units (volt, hertz, second).
- NASA Glenn Research Center: Switching power conversion fundamentals.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.