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Branch Circuit Wire Size Calculation

PASS

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Circuit inputs and coordinated result

Project: —
Location: —
Prepared by: —
System: Single-phase AC
Source voltage: 120 V
Loads: 0 A continuous + 16 A noncontinuous
Conductor: Copper · stranded
Insulation / terminals: 90°C (194°F) / 75°C (167°F)
Ambient / CCC: 30°C (86°F) · 2 current-carrying
Run / target: 100 ft · 3% maximum
Power factor / reactance: 1 · 0.08 mΩ/m
Protective device: 20 A confirmed

Calculated decision

Required ampacity: 16 A
Ampacity minimum: 12 AWG
Voltage-drop minimum: 8 AWG
Final phase conductor: 8 AWG Copper
Calculated voltage drop: 2.62 V · 2.19%
Wire-type EGC: 8 AWG Copper
Governing check: Voltage drop governs
Planning status: PASS

Supported planning scope

For common DC, single-phase, and balanced three-phase circuits using one non-parallel conductor per phase. The calculator does not model neutrals, motors, HVAC, welders, EV-specific rules, taps, dwelling allowances, hazardous locations, or local amendments.

Guided circuit inputs

Circuit load

SystemSource voltage — VConductor materialConstructionProduct availability is confirmed during the conduit handoff.Insulation temperature ratingEquipment terminal ratingUse the lowest applicable marked termination rating.Temperature input unitNEC table ranges are evaluated in Celsius.Ambient temperature — °CEquivalent: 86°F.Current-carrying conductorsDetermine neutral treatment before entering this count.Continuous load — ANoncontinuous load — AOne-way circuit length — ftMaximum voltage drop — %Power factorReactance — mΩ/mPlanning input; verify the installed wiring method.Conductor temperature for voltage drop — °CEquivalent: 167°F.Confirmed protective device — AThis calculator does not select the breaker or fuse.Equipment grounding conductor material

Coordinated result

How the final size was selected

Use this conductor plan in Conduit Size

Transfers 2 × 8 AWG Copper circuit conductors and 1 × 8 AWG Copper equipment grounding conductor.

Continue to Conduit Size

Load requirement

16 A

16 A + 125% × 0 A.

Ampacity minimum

12 AWG

20 A planning limit after the entered conditions.

Voltage-drop minimum

8 AWG

First supported size at or below the 3% target.

Final coordinated size

8 AWG

Voltage drop governs; calculated drop 2.19%.

Protective-device review: planning checks pass

20 A device · required load ampacity 16 A · final conductor planning limit 50 A.

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Export this coordinated circuit plan

The report retains ampacity, voltage-drop, protective-device, grounding, and governing-size calculations.

Continue this calculation

Send these inputs to another calculator

The destination opens with compatible conduit and cable inputs already selected. This calculator and its results remain unchanged.

Continue to Conduit SizeTransfers 2 circuit conductors and one EGC as separate rows. Select exact insulation and manufacturer products so published outside diameters are used.Open calculator →

What this coordinates

One visible planning sequence

The result reuses the site’s ampacity, voltage-drop, and equipment-grounding engines. The larger of the ampacity and voltage-drop sizes becomes the installed circuit conductor, then the entered protective device and any phase-conductor increase are applied to the wire-type EGC.

What you must verify

No hidden installation assumptions

Confirm the protective device, neutral treatment, conductor count, wiring method, exact conductor product, raceway, local amendments, equipment instructions, and authority-having-jurisdiction requirements before installation.