MOSFET Power Dissipation Calculator
Enter drain current, Rds(on), duty cycle, voltage, switching times and frequency to split MOSFET losses into conduction and switching, plus the total.
Use the MOSFET Power Dissipation Calculator
MOSFET Operating Parameters
Power Dissipation Breakdown
Conduction Loss
0.00 W
I² × Rds(on) × duty cycle
Switching Loss
0.00 W
0.5 × V × I × (tr+tf) × f
Total Power Dissipation
0.00 W
Conduction
Switching
Summary
This calculator splits total MOSFET power dissipation into its two physical sources: conduction loss from current flowing through Rds(on) while the channel is on, and switching loss from the finite rise and fall time at every turn-on and turn-off transition. Entering both as one blended number hides which loss actually dominates, which leads to wrong heatsink and gate-driver decisions. The tool computes each term separately and sums them so the split stays visible.
How it works
- Enter the drain current the MOSFET carries while conducting.
- Enter Rds(on) from the datasheet at the expected junction temperature.
- Enter the duty cycle, the fraction of each switching period the MOSFET is on.
- Enter the supply (drain) voltage the MOSFET blocks when off.
- Enter rise time and fall time from the datasheet or a scope measurement.
- Enter the switching frequency; the calculator computes conduction loss, switching loss, and their sum.
Use cases
- Sizing a heatsink for a buck or boost converter MOSFET.
- Comparing two MOSFETs with different Rds(on) and switching-time tradeoffs.
- Checking whether a design is conduction-limited or switching-limited before changing frequency.
- Estimating losses when raising switching frequency to shrink an inductor.
- Verifying a MOSFET selection against a thermal budget before a board spin.
- Teaching the difference between conduction and switching loss in a power electronics course.
Frequently Asked Questions
Last updated: 2026-09-09 · Reviewed by Nham Vu