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Texas electrician exam formula sheet

PSI gives you no formula sheet and you cannot bring paper into the exam, so this sheet is for studying: learn the formulas and the NEC section where each value lives. Every formula links to its practice.

Texas electrician exam formula sheet · 2026 NEC

√3 1.732 (three-phase)

K for copper 12.9 Ω·cmil/ft

K for aluminum 21.2 Ω·cmil/ft

Continuous load 125% (3 hours or more)

Passing score 70% on each part

Dwelling load calculations

Dwelling optional load calculation120.82(A) · 120.82(B)

General (VA) = 8,000 + 40% × (2 VA × ft² + 1,500 × circuits + nameplates − 8,000)Total (VA) = General + Largest heat or AC choice + EVSE at 100%Service (A) = Total (VA) ÷ 240 V

Dwelling standard load calculation120.41 · 120.52(A), 120.52(B)

Lighting (VA) = Area (ft²) × 2 + 1,500 × (small-appliance + laundry circuits), then Table 120.45Total (VA) = Lighting demand + 75% of 4+ appliances + Dryer + Range + Larger of heat or ACService (A) = Total (VA) ÷ 240 V

Fastened appliance demand load120.53 · 120.54, 120.55, 120.57

Four or more: Demand (VA) = 75% × Sum of nameplatesThree or fewer: Demand (VA) = Sum of nameplates

Commercial load calculations

Commercial lighting loadTable 120.42(A) · 120.5(E)

Lighting load (VA) = Floor area (ft²) × Unit load from Table 120.42(A) (VA/ft²)Continuous feeder sizing (VA) = Lighting load × 1.25Show window (VA) = 200 × Length (ft); Sign outlet = 1,200 VA

Receptacle load120.14(I) · 120.14(H)

Receptacle load (VA) = 180 × yokes + multioutlet assembly loadDemand (VA) = 10,000 + 50% × (Receptacle load − 10,000)

Conductors and overcurrent

Ampacity correction and adjustmentTable 310.16 · Table 310.15(B)(1)(1)

Adjusted ampacity (A) = Table ampacity (A) × Temperature correction factor × Adjustment factorRequired table ampacity (A) = Load (A) ÷ (Correction factor × Adjustment factor)

Conductor sizingTable 310.16 · 110.14(C)(1)

Required ampacity (A) = Load (A), from the termination temperature columnColumn: 60 °C if the circuit is 100 A or less and terminals are not marked 75 °C; 75 °C if over 100 A

Continuous loadsArticle 100, Continuous Load · 210.19(A)

Minimum rating or ampacity (A) = 1.25 × Continuous load (A) + 1.00 × Noncontinuous load (A)Maximum continuous load (A) = Breaker rating (A) ÷ 1.25 (80% of the rating)

Overcurrent device sizing240.4 · 240.4(B)

800 A or less: Largest device (A) = next standard rating at or above the conductor ampacity (A)Over 800 A: Largest device (A) = standard rating at or below the conductor ampacity (A)14, 12, 10 AWG: never above the 240.4(D) limit

Voltage dropChapter 9, Table 8 · 210.19 Informational Note

Single-phase: VD (V) = 2 × K × I × L ÷ CMThree-phase: VD (V) = 1.732 × K × I × L ÷ CMMinimum CM = 2 (or 1.732) × K × I × L ÷ Allowed VD (V)

Motors

Motor branch-circuit conductors430.22 · 430.6(A)(1)

Minimum ampacity (A) = 1.25 × table full-load current (A)Conductor size = smallest size in Table 310.16, terminal temperature column, with ampacity ≥ minimum ampacity

Motor feeders430.24 · 430.62(A)

Feeder ampacity (A) = 1.25 × largest motor FLC + sum of other motor FLCs + 1.25 × continuous other loads + noncontinuous other loads

Feeder OCPD (A) ≤ largest motor branch OCPD rating + sum of other motor FLCs, rounded down to a standard size

Motor full-load current430.6(A)(1) · 430.6(A)(2)

Conductors and short-circuit protection: FLC (A) = Table 430.248 or 430.250 value for the hp and voltageSeparate overload protection: current (A) = motor nameplate current

Motor overload protection430.32(A)(1) · 430.32(C)

Service factor ≥ 1.15 or temperature rise ≤ 40 °C: Overload (A) ≤ 1.25 × nameplate currentAll other motors: Overload (A) ≤ 1.15 × nameplate current

Motor short-circuit protection430.52(C)(1) · Table 430.52(C)(1)

Maximum rating (A) = Table FLC (A) × Table 430.52(C)(1) percentIf that is not a standard size, the next standard size up in 240.6(A) is allowed (Exception No. 1)

Boxes and raceways

Box fill314.16(B) · Table 314.16(A)

Minimum box volume (in³) = Total conductor count × Volume allowance for the size (in³)

Conduit fillChapter 9, Table 1 · Chapter 9, Notes to Tables

Total conductor area (in²) = Σ (number of conductors × area of one, Table 5)Pick the smallest trade size whose allowed area (Table 4, 40% column) ≥ total conductor areaMax conductors of one size = allowed area ÷ area of one, round up only at 0.8 or more

Pull box sizing314.28(A)(1) · 314.28(A)(2)

Straight pull: Length (in.) ≥ 8 × largest trade size

Angle or U pull: Distance to opposite wall (in.) ≥ 6 × largest trade size in the row + sum of the other trade sizes in that row

Same conductor: Distance between entries (in.) ≥ 6 × larger trade size

Grounding and bonding

Equipment grounding conductor sizingTable 250.122 · 250.122(A)

EGC size = Table 250.122 row for the overcurrent device rating (A)Increased EGC (cmil) = Table EGC (cmil) × Increased ungrounded size (cmil) ÷ Normal ungrounded size (cmil)

Grounding electrode conductor sizingTable 250.66 · 250.66(A)

GEC size = Table 250.66 row for the largest ungrounded service conductorParallel sets: Equivalent area (cmil) = Sets × Area of one conductor (cmil)

Rod only: never more than 6 AWG Cu. Concrete-encased only: never more than 4 AWG Cu. Ring only: never more than the ring conductor

Transformers

Transformer currentTable 450.5(B) · 240.21(C)

Single-phase: I (A) = kVA × 1,000 ÷ E (V)Three-phase: I (A) = kVA × 1,000 ÷ (E (V) × 1.732)Turns ratio = Ep ÷ Es = Np ÷ Ns = Is ÷ Ip

Transformer overcurrent protectionTable 450.5(B) · 240.6(A)

Primary only (Ip 9 A or more): Max primary OCPD (A) = Ip × 1.25, next standard size up allowedPrimary and secondary: Max primary OCPD (A) = Ip × 2.50, no rounding upPrimary and secondary (Is 9 A or more): Max secondary OCPD (A) = Is × 1.25, next standard size up allowed

Electrical theory

Ohm's law and power120.5 · Chapter 9, Table 8

E (V) = I (A) × R (Ω)P (W) = E (V) × I (A) = I² × R = E² ÷ R

Power factor and efficiency430.6(A)(1) · Table 430.250

True power (W) = Apparent power (VA) × PFEfficiency (%) = Output (W) ÷ Input (W) × 100Motor output (W) = hp × 746

Series and parallel circuitsChapter 9, Table 8

Series: RT (Ω) = R1 + R2 + R3Parallel: RT (Ω) = 1 ÷ (1/R1 + 1/R2 + 1/R3)Two in parallel: RT (Ω) = (R1 × R2) ÷ (R1 + R2)

Three-phase power120.5 · 120.5

Three-phase: I (A) = VA ÷ (E × 1.732)Three-phase: kVA = E (V) × I (A) × 1.732 ÷ 1,000Single-phase: I (A) = VA ÷ E (V)

Written in our own words from the 2026 NEC. Section numbers point to your own code book; values such as ampacities and motor currents are looked up there, not printed here. texaselectricianexam