Electrical calculator

MOSFET Total Loss Calculator

MOSFET device dissipation from conduction + hard-switching + optional Coss/Eoss, plus optional gate-drive and Qrr commutation. Tj uses P_device, not associated total. Omitted terms are not treated as 0 W. Runs locally in your browser.

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Trust summary CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance

Input interpretation: Enter values to calculate.
Result: —
Assurance: Engineering
Declared partition coverage: PASS · 4/4 declared partitions (on_interval_rms, dc, with-optional-terms, invalid-domain) · Matrix
Known limitations: Composite conduction+switching; gate/Qrr excluded from device Tj path
Core CVP does not include live graph, viewport, or pointer interaction.
Model: MOSFET device dissipation P_cond+P_sw+P_coss, associated P_total = P_device+P_gate+P_rr, and optional Tj_est = Ta+P_device·Rth_JA. Omitted optional terms are listed in terms_omitted (unknown ≠ 0).
Scope: Hard-switching linear V/I overlap.
Verification: Engine tested · Source checked · v1.1.2 · CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance· View Manifest · CVP overview · Specification
Versions: Calculation 1.1.2 · CVP protocol 1.0.0-proposed
CVP identity: 8/8 property · digest e1e9664a3ef4
Legacy regression: 39/39 tests · Production surface contract 18/18
Reference: O1 model · O2 expected_values · O2 numerical_behavior
Interfaces: PASS · UI (SSR) / REST / MCP — ui-ssr is query-result HTML, not a live browser session.
Supplemental domain review: Internal · Pass · electrical-engineer · 2026-08-19
Named expert review: Not performed
CVP suite: 3/3 golden · 22/22 CVP boundary · 19/19 invalid · 8/8 property · 1/1 cross-interface · 18/18 CVP contract · Manifest
Sources: Infineon — OptiMOS device selection for synchronous rectification — Conduction losses P_cond = I_RMS² × RDS(on)
Texas Instruments SLYT664 — MOSFET power losses and how they affect power-supply efficiency — Conduction, switching, gate, and output capacitance
Texas Instruments SLUA618 — Fundamentals of MOSFET and IGBT Gate Driver Circuits — Gate-drive energy split among driver and gate resistance
Erickson & Maksimović — Fundamentals of Power Electronics — Semiconductor conduction and switching loss
Sources
Evidence: 7 legacy golden · 22 legacy boundary · legacy regression suite · 3/3 oracle-backed golden · 19/19 invalid · Artifact integrity PASS · CalculatorX electrical review (EE-001)
Semantic contract: PASS

Full verification

Manifest identity, reference classes, interfaces, suite, and production records.

Formulas

Core equations used by this calculator.

Device dissipationP_device = P_cond + P_sw + P_coss

Associated loss budgetP_total = P_device + P_gate + P_rr

ConductionP_cond = I² × Rds_Tj × D (D only for on-interval RMS)

SwitchingP_sw = ½ × Vds × Id × (tr + tf) × f_sw

Gate-driveP_gate = Qg × Vdrive × f_sw (not in P_device / Tj)

Coss / EossP_coss = ½ × Coss × Vds² × f_sw or Eoss × f_sw

Qrr commutationP_rr = Qrr × Vds × f_sw (usually complementary switch)

Junction (optional)Tj_est = Ta + P_device × Rth_JA

iComposes electrical.mosfet.conduction_loss and electrical.mosfet.switching_loss. Coss ½CV² is a lumped equivalent — prefer datasheet Eoss at Vds. Overlap P_sw plus P_coss may overestimate due to double counting; first-order only — validate against measured Eon/Eoff. Not soft-switching or Eon/Eoff tables.

How to use

Enter conduction I and Rds(on)

Choose current_basis (DC / on-interval RMS / full-cycle RMS). Optional Advanced Rds(Tj).

Enter switching Vds, Id, tr, tf, f_sw

Hard-switching overlap estimate. Id is the switched current — often the same as conduction I for rectangular PWM.

Optional gate, Coss/Eoss, Qrr, thermal

Qg+Vdrive together (gate-drive, not die loss). Eoss preferred over lumped Coss. Qrr·Vds·f is commutation loss, usually the complementary switch. Ta + Rth_JA uses P_device.

Example calculations

Common configurations with formula and result.

PWM on-interval RMS

10 A on-interval · D=0.5 · 50 mΩ · 48 V · 10 A · 50 ns / 40 ns · 100 kHz

2.5 W + 2.16 W

P_device = 4.66 W

DC continuous

DC 10 A · 50 mΩ · 48 V · 10 A · 50 ns / 40 ns · 100 kHz

5 W + 2.16 W

P_device = P_total = 7.16 W

Add gate, Eoss, Qrr

DC core + Qg=50 nC · Vdrive=10 V · Eoss=10 µJ · Qrr=100 nC

P_device += 1; P_gate=0.05; P_rr=0.48

P_device = 8.16 W · P_total = 8.69 W

Hot Rds ratio 1.44

DC core + rds_ratio=1.44

P_cond = 7.2 W

P_device = P_total = 9.36 W

MOSFET Total Loss calculator specification

Version 1.1.2 · Engine tested · Supplemental domain review · Internal · 2026-08-19

Calculation status

Engine tested 39/39 tests · Production surface contract 18/18
Supplemental domain review Internal · Pass · electrical-engineer · 2026-08-19
Named expert review Not performed
Calculation version 1.1.2

Review policy · Evidence · Reviewed by CalculatorX electrical review (EE-001) (electrical-engineer)

Definition: First-order MOSFET loss workspace. Device dissipation is P_device = P_cond + P_sw + P_coss. Associated total is P_total = P_device + P_gate + P_rr. Gate-drive and Qrr commutation are not this MOSFET’s junction loss. Omitted optional terms are not included (unknown ≠ 0), even though JSON keeps numeric 0.
What it calculates: MOSFET device dissipation P_cond+P_sw+P_coss, associated P_total = P_device+P_gate+P_rr, and optional Tj_est = Ta+P_device·Rth_JA. Omitted optional terms are listed in terms_omitted (unknown ≠ 0).
Inputs: I, Rds, current_basis, Vds, Id, tr, tf, f_sw required
current_basis — required: dc | on_interval_rms | full_cycle_rms
Optional D, Rds(Tj) fields, Qg+Vdrive, Coss or Eoss, Qrr, Ta_C+Rth_JA
Outputs: P_device_W (die) and P_total_W (associated), plus per-term P_cond_W, P_sw_W, P_gate_W, P_coss_W, P_rr_W
terms_applied, terms_omitted, terms_in_device, dominant_included
Optional Tj_est_C when Ta_C and Rth_JA are both set (from P_device_W)
Formula: P_device = P_cond + ½·Vds·Id·(tr+tf)·f + (½·Coss·Vds²·f | Eoss·f); P_total = P_device + Qg·Vdrive·f + Qrr·Vds·f; Tj = Ta + P_device·Rth
Assumptions: Hard-switching linear V/I overlap.
Conduction current_basis contract is identical to electrical.mosfet.conduction_loss.
Coss term is lumped or Eoss-at-Vds — not a Qoss(V) integral.
P_gate is drive-circuit power, not die dissipation.
P_rr is commutation loss, usually not this MOSFET.
Tj_est is steady-state RthJA of P_device only.
Units: A, Ω, V, s, Hz, C, F, J, °C, °C/W → W
Boundary conditions: Missing required conduction or switching field → MISSING_REQUIRED_INPUT
≤ 0 on required positives → VALUE_MUST_BE_POSITIVE
Non-finite number → INVALID_NUMBER
D not in (0, 1] when applied → FRACTION_OUT_OF_RANGE
Qg XOR Vdrive → NEEDS_TWO_INPUTS
Unknown current_basis, temperature_model, or coss_model → INVALID_MODE
coss_model=eoss without Eoss, or coss_eq without Coss → MISSING_REQUIRED_INPUT
Optional Qg/Coss/Eoss/Qrr if present must be > 0 → VALUE_MUST_BE_POSITIVE (explicit 0 is not yet a supported known-zero state; omit for unknown)
Coss and Eoss both set → warning EOSS_OVERRIDES_COSS (Eoss wins)
Only one of Ta_C / Rth_JA → warning THERMAL_NOT_APPLIED
current_basis=dc with f_sw > 0 → info DC_CURRENT_WITH_SWITCHING
Qg+Vdrive present → info GATE_NOT_IN_DEVICE
Qrr present → info QRR_NOT_IN_DEVICE
Example: I=10, Rds=0.05, current_basis=on_interval_rms, D=0.5, Vds=48, Id=10, tr=50ns, tf=40ns, f_sw=100kHz → P_device_W=4.66
Validation cases: 6 published on this page · 39/39 tests · Production surface contract 18/18 · View evidence
on-interval RMS 10 A, D=0.5, 50 mΩ, 48 V, 10 A, 50 ns, 40 ns, 100 kHz → P_cond=2.5, P_sw=2.16, P_device=4.66
dc 10 A, 50 mΩ, 48 V, 10 A, 50 ns, 40 ns, 100 kHz → P_cond=5, P_sw=2.16, P_device=P_total=7.16, 3 optional terms omitted
+ Qg=50 nC, Vdrive=10, Eoss=10 µJ, Qrr=100 nC → P_device=8.16, P_total=8.69
+ Qg, Qrr, Ta=25, Rth=10 without Coss → Tj_est=96.6 from P_device=7.16, not from P_total=7.69
Coss=1 nF → P_coss=0.1152 in P_device
Qg without Vdrive → error NEEDS_TWO_INPUTS
Sources: Infineon — OptiMOS device selection for synchronous rectification — Conduction losses P_cond = I_RMS² × RDS(on) · accessed 2026-08-14
Supports: MOSFET RMS current (not converter output current) for conduction; first-order loss stack
Texas Instruments SLYT664 — MOSFET power losses and how they affect power-supply efficiency — Conduction, switching, gate, and output capacitance · accessed 2026-08-14
Supports: P_cond = I_RMS²·RDS(on); P_sw ≈ ½·V·I·(tr+tf)·f; P_gate = Qg·Vdrive·f
Texas Instruments SLUA618 — Fundamentals of MOSFET and IGBT Gate Driver Circuits — Gate-drive energy split among driver and gate resistance · accessed 2026-08-16
Supports: P_gate is not entirely dissipated in the MOSFET junction
Erickson & Maksimović — Fundamentals of Power Electronics — Semiconductor conduction and switching loss
Supports: I_rms conduction and linear-transition switching estimates
Last reviewed: 2026-08-19
Reviewed by: CalculatorX electrical review (EE-001) (electrical-engineer)
Calculation version: 1.1.2

Background

Interpretation and common distinctions.

Compose MOSFET device dissipation from the conduction and switching probes, plus optional Coss/Eoss. Optional gate-drive and Qrr commutation are associated converter terms — they are not this MOSFET’s junction loss.

Default example: On-interval RMS 10 A · D = 0.5 · 50 mΩ + 48 V · 10 A · 50 ns / 40 ns · 100 kHz → P_device = 4.66 W (2.5 W conduction + 2.16 W switching). Three optional terms are not included (unknown ≠ 0).

DC 10 A continuous (no duty) is 7.16 W. Add Qg = 50 nC, Vdrive = 10 V, Eoss = 10 µJ, Qrr = 100 nC to that DC core → P_device = 8.16 W, associated loss budget = 8.69 W. Gate-drive (0.05 W) and Qrr (0.48 W) stay out of Tj.

Supported and not supported

Supported

current_basis and optional Rds(Tj) via the conduction engine
Hard-switching overlap + optional gate-drive (not in P_device)
coss_model: none | coss_eq | eoss
Qrr-related commutation P_rr = Qrr · Vds · f_sw (associated, not this die)
Optional Tj_est = Ta + P_device · Rth_JA
terms_omitted so omitted optionals are not presented as 0 W
API / MCP via electrical.mosfet.total_loss

Not supported

Soft-switching / ZVS / ZCS
Eon/Eoff table interpolation or Qoss(V) curves
Splitting P_gate between driver, Rg, and Rg,int
Compact thermal impedance Zth
Parallel FET current sharing

Agent / API notes

Capability id: electrical.mosfet.total_loss · tool id: mosfet-total-loss · pin calculation_version: 1.1.2.

Required: I, Rds, current_basis, Vds, Id, tr, tf, f_sw. current_basis is required (same contract as the conduction probe v1.2.1+). The published UI default is on_interval_rms with D=0.5. Prefer current_basis=dc when I is continuous. DC + switching frequency together is an engineering hint, not an error.

Omitting coss_model infers eoss if Eoss is set, else coss_eq if Coss is set, else none.

JSON keeps P_gate_W / P_coss_W / P_rr_W = 0 when omitted for compatibility; read terms_omitted (unknown ≠ 0). Providing Qrr=0 (or Qg/Coss/Eoss = 0) is currently rejected (VALUE_MUST_BE_POSITIVE); omit the field for unknown. Tj_est_C uses P_device_W.

Stable error codes: MISSING_REQUIRED_INPUT, INVALID_NUMBER, VALUE_MUST_BE_POSITIVE, FRACTION_OUT_OF_RANGE, INVALID_MODE, NEEDS_TWO_INPUTS.

Warning codes: those of the conduction probe, plus COSS_NOT_APPLIED, EOSS_OVERRIDES_COSS, THERMAL_NOT_APPLIED, DC_CURRENT_WITH_SWITCHING, GATE_NOT_IN_DEVICE, QRR_NOT_IN_DEVICE.

Other calculators in this family: ADC Error Budget Calculator, Diode Equation Calculator, LDO Thermal Calculator, LED Resistor Calculator, MOSFET Conduction Loss Calculator, MOSFET Junction Temperature Calculator, MOSFET Switching Loss Calculator, MOSFET Threshold & Overdrive Calculator . Explore all Semiconductor.

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Frequently asked questions

Key distinctions behind the calculation.

How is this different from the conduction and switching calculators?

Those remain the single-term probes. This workspace composes them and adds first-order Coss/Eoss, reverse recovery, and an optional RthJA junction estimate from P_device. Same engines, same current_basis and Rds(Tj) contract.

Why does an omitted term say Not included instead of 0 W?

Optional gate, Coss/Eoss, and Qrr are unknown until entered. Unknown is not zero. The API still returns numeric 0 for omitted P_gate/P_coss/P_rr so agents stay compatible, and lists them in terms_omitted.

Should I use Coss or Eoss?

Prefer datasheet Eoss at the switched Vds (P = Eoss·f). ½·Coss·V²·f is a lumped equivalent and can disagree with the nonlinear Coss(V) curve. Adding P_coss on top of the linear overlap P_sw can double-count some capacitive energy. The sum may overestimate; use as a first-order estimate and validate against measured Eon/Eoff where accuracy matters.

Is P_rr this MOSFET’s dissipation?

Usually not. P_rr = Qrr·Vds·f is recovered-charge commutation loss, commonly assigned to the complementary switch. It is included in associated P_total but excluded from P_device and Tj_est. It is not a full Irr(t) waveform model.

Is P_gate MOSFET junction dissipation?

No. Gate-drive energy is shared among the driver, external gate resistor, and the MOSFET internal gate resistance. Tj_est = Ta + P_device·RθJA does not include P_gate.

When should I use DC current with a switching frequency?

current_basis=dc assumes continuous current through the MOSFET (duty ≈ 1). If the FET is PWM-switched, use on-interval RMS with D, or full-cycle MOSFET RMS. The published default example is on-interval RMS with D=0.5, not a DC always-on case.

Does this include soft-switching?

No. ZVS/ZCS, Eon/Eoff tables, and Qoss(V) interpolation are out of scope.