{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"wire-voltage-drop"},"result":{"entity_type":"calculator","id":"wire-voltage-drop","calculator_id":"wire-voltage-drop","canonical_url":"https://tttkmbb.com/engineering/wire-voltage-drop","name":"Wire Voltage Drop Calculator","title":"Wire Voltage Drop Calculator – Drop in Volts and Percent by AWG or mm², Length, Current and Material","category":"engineering","category_name":"Engineering & Automotive","tool_name":"calculate_wire_voltage_drop","featured_mcp_tool":false,"description":"Computes the resistance of a copper or aluminium conductor from its AWG gauge or cross-section and one-way length, then the voltage drop, percentage drop, voltage at the load and power lost for DC, single-phase or three-phase circuits.","use_when":"You are sizing a cable run (solar, automotive, 12 V LED, branch circuit) and need to know whether the voltage drop stays within a limit such as 3 %.","do_not_use_when":"You need ampacity (heating limits, which depend on insulation and installation method, not covered here), or the conductor is not copper or aluminium.","inputs":[{"name":"voltage_v","label":"Source voltage","type":"number","unit":"V","required":true,"max":100000,"exclusive_min":0,"description":"Supply voltage (line-to-line for three-phase).","example":12},{"name":"current_a","label":"Load current","type":"number","unit":"A","required":true,"min":0,"max":100000,"description":"Current carried by the conductor in amperes.","example":10},{"name":"length_m","label":"One-way length","type":"number","unit":"m","required":true,"max":100000,"exclusive_min":0,"description":"Distance from source to load in metres (1 ft = 0.3048 m); the return conductor is accounted for automatically.","example":5},{"name":"awg","label":"Wire gauge (AWG)","type":"integer","required":false,"min":-3,"max":40,"description":"American Wire Gauge number. Use 0 for 1/0, −1 for 2/0, −2 for 3/0, −3 for 4/0. Give either awg or cross_section_mm2.","example":12},{"name":"cross_section_mm2","label":"Cross-section","type":"number","unit":"mm²","required":false,"max":2000,"exclusive_min":0,"description":"Conductor cross-sectional area in mm² (metric cable sizes 1.5, 2.5, 4, 6, 10 …). Give either awg or cross_section_mm2."},{"name":"material","label":"Conductor material","type":"enum","required":false,"default":"copper","values":[{"value":"copper","label":"Copper (1.724×10⁻⁸ Ω·m)","aliases":["cu"]},{"value":"aluminium","label":"Aluminium (2.65×10⁻⁸ Ω·m)","aliases":["aluminum","al"]}],"description":"Conductor material; resistivity at 20 °C.","example":"copper"},{"name":"phase","label":"Circuit type","type":"enum","required":false,"default":"dc","values":[{"value":"dc","label":"DC (two conductors)"},{"value":"single_phase","label":"Single-phase AC (two conductors)","aliases":["single","1ph","ac"]},{"value":"three_phase","label":"Three-phase AC (balanced)","aliases":["three","3ph"]}],"description":"DC and single-phase count the outgoing and return conductor (×2); balanced three-phase uses ×√3.","example":"dc"},{"name":"conductor_temperature_c","label":"Conductor temperature","type":"number","unit":"°C","required":false,"default":20,"min":-50,"max":200,"description":"Operating temperature of the conductor; resistance rises about 0.4 % per °C above 20 °C (use 75 for a fully loaded cable).","example":20}],"outputs":[{"name":"conductor_diameter_mm","label":"Conductor diameter","type":"number","unit":"mm","decimals":3,"description":"Bare conductor diameter (from AWG or derived from the area)."},{"name":"cross_section_mm2","label":"Cross-section","type":"number","unit":"mm²","decimals":3,"description":"Conductor area."},{"name":"resistance_per_km_ohm","label":"Resistance per km","type":"number","unit":"Ω/km","decimals":4,"description":"ρ / A at the given temperature, per conductor."},{"name":"conductor_resistance_ohm","label":"One-way resistance","type":"number","unit":"Ω","decimals":5,"description":"Resistance of one conductor over length_m."},{"name":"voltage_drop_v","label":"Voltage drop","type":"number","unit":"V","decimals":3,"description":"2 × I × R (DC, single-phase) or √3 × I × R (three-phase)."},{"name":"voltage_drop_percent","label":"Voltage drop","type":"number","unit":"%","decimals":2,"description":"voltage_drop_v / voltage_v × 100."},{"name":"voltage_at_load_v","label":"Voltage at load","type":"number","unit":"V","decimals":3,"description":"voltage_v − voltage_drop_v."},{"name":"power_loss_w","label":"Power lost in the cable","type":"number","unit":"W","decimals":3,"description":"2 × I² × R (DC, single-phase) or 3 × I² × R (three-phase)."},{"name":"assessment","label":"Assessment","type":"string","decimals":4,"description":"Comparison with the common 3 % (branch circuit) and 5 % (total) voltage-drop recommendations (NEC informational note)."}],"input_schema":{"type":"object","properties":{"voltage_v":{"description":"Supply voltage (line-to-line for three-phase). Unit: V.","type":"number","maximum":100000,"exclusiveMinimum":0,"examples":[12],"x-unit":"V"},"current_a":{"description":"Current carried by the conductor in amperes. Unit: A.","type":"number","minimum":0,"maximum":100000,"examples":[10],"x-unit":"A"},"length_m":{"description":"Distance from source to load in metres (1 ft = 0.3048 m); the return conductor is accounted for automatically. Unit: m.","type":"number","maximum":100000,"exclusiveMinimum":0,"examples":[5],"x-unit":"m"},"awg":{"description":"American Wire Gauge number. Use 0 for 1/0, −1 for 2/0, −2 for 3/0, −3 for 4/0. Give either awg or cross_section_mm2.","type":"integer","minimum":-3,"maximum":40,"examples":[12]},"cross_section_mm2":{"description":"Conductor cross-sectional area in mm² (metric cable sizes 1.5, 2.5, 4, 6, 10 …). Give either awg or cross_section_mm2. Unit: mm².","type":"number","maximum":2000,"exclusiveMinimum":0,"x-unit":"mm²"},"material":{"description":"Conductor material; resistivity at 20 °C.","type":"string","enum":["copper","aluminium"],"default":"copper","examples":["copper"]},"phase":{"description":"DC and single-phase count the outgoing and return conductor (×2); balanced three-phase uses ×√3.","type":"string","enum":["dc","single_phase","three_phase"],"default":"dc","examples":["dc"]},"conductor_temperature_c":{"description":"Operating temperature of the conductor; resistance rises about 0.4 % per °C above 20 °C (use 75 for a fully loaded cable). Unit: °C.","type":"number","minimum":-50,"maximum":200,"default":20,"examples":[20],"x-unit":"°C"}},"additionalProperties":false,"required":["voltage_v","current_a","length_m"]},"output_schema":{"type":"object","properties":{"conductor_diameter_mm":{"description":"Bare conductor diameter (from AWG or derived from the area). Unit: mm.","type":"number","x-unit":"mm"},"cross_section_mm2":{"description":"Conductor area. Unit: mm².","type":"number","x-unit":"mm²"},"resistance_per_km_ohm":{"description":"ρ / A at the given temperature, per conductor. Unit: Ω/km.","type":"number","x-unit":"Ω/km"},"conductor_resistance_ohm":{"description":"Resistance of one conductor over length_m. Unit: Ω.","type":"number","x-unit":"Ω"},"voltage_drop_v":{"description":"2 × I × R (DC, single-phase) or √3 × I × R (three-phase). Unit: V.","type":"number","x-unit":"V"},"voltage_drop_percent":{"description":"voltage_drop_v / voltage_v × 100. Unit: %.","type":"number","x-unit":"%"},"voltage_at_load_v":{"description":"voltage_v − voltage_drop_v. Unit: V.","type":"number","x-unit":"V"},"power_loss_w":{"description":"2 × I² × R (DC, single-phase) or 3 × I² × R (three-phase). Unit: W.","type":"number","x-unit":"W"},"assessment":{"description":"Comparison with the common 3 % (branch circuit) and 5 % (total) voltage-drop recommendations (NEC informational note).","type":"string"}}},"formula":"d_mm = 0.127 × 92^((36 − awg) / 39); A = π d² / 4; R = ρ × (1 + α (T − 20)) × length_m / A; voltage_drop_v = k × current_a × R with k = 2 (dc, single_phase) or √3 (three_phase); ρ_copper = 1.724e-8 Ω·m, ρ_aluminium = 2.65e-8 Ω·m","method":"Resistive (DC) drop only; conductor reactance and power factor are ignored, which is accurate for cables up to about 25 mm² / 4 AWG at 50–60 Hz. The 3 %/5 % limits follow NEC 210.19(A) and 215.2(A) informational notes and similar rules in IEC 60364-5-52.","sources":[{"name":"Wikipedia – American wire gauge","url":"https://en.wikipedia.org/wiki/American_wire_gauge","type":"reference","retrieved_at":"2026-09-24"},{"name":"Wikipedia – Electrical resistivity and conductivity","url":"https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity","type":"reference","retrieved_at":"2026-09-24"},{"name":"NFPA 70 – National Electrical Code (voltage drop informational notes 210.19(A), 215.2(A))","url":"https://www.nfpa.org/codes-and-standards/nfpa-70-standard-development/70","type":"standard","retrieved_at":"2026-09-24"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"12 V, 10 A, 5 m of 12 AWG copper","inputs":{"voltage_v":12,"current_a":10,"length_m":5,"awg":12},"expected":{"conductor_diameter_mm":2.053,"cross_section_mm2":3.309,"resistance_per_km_ohm":5.2104,"conductor_resistance_ohm":0.02605,"voltage_drop_v":0.521,"voltage_drop_percent":4.34,"voltage_at_load_v":11.479,"power_loss_w":5.21},"url":"https://tttkmbb.com/api/v1/calculate/wire-voltage-drop?voltage_v=12&current_a=10&length_m=5&awg=12"},{"name":"230 V single-phase, 16 A, 30 m of 2.5 mm² copper","inputs":{"voltage_v":230,"current_a":16,"length_m":30,"cross_section_mm2":2.5,"phase":"single_phase"},"expected":{"resistance_per_km_ohm":6.896,"conductor_resistance_ohm":0.20688,"voltage_drop_v":6.62,"voltage_drop_percent":2.88,"voltage_at_load_v":223.38,"power_loss_w":105.923},"url":"https://tttkmbb.com/api/v1/calculate/wire-voltage-drop?voltage_v=230&current_a=16&length_m=30&cross_section_mm2=2.5&phase=single_phase"}],"faq":[{"q":"Is the length one-way or round trip?","a":"Enter the one-way distance from source to load; the calculator doubles it for DC and single-phase circuits and uses √3 for balanced three-phase."},{"q":"How much drop is acceptable?","a":"The NEC recommends at most 3 % on a branch or feeder and 5 % overall for efficiency; low-voltage systems (12 V solar or automotive) often need thicker cable than the current alone suggests to stay under 3 %."}],"tags":["voltage drop","wire gauge","awg","cable size","voltage drop calculator","wire resistance"],"related":[{"calculator_id":"ohms-law","reason":"V = I·R for the conductor resistance."},{"calculator_id":"electric-power","reason":"Load current from power and voltage."},{"calculator_id":"led-resistor","reason":"Low-voltage LED circuits where drop matters."}],"links":{"html":"https://tttkmbb.com/engineering/wire-voltage-drop","markdown":"https://tttkmbb.com/engineering/wire-voltage-drop.md","json":"https://tttkmbb.com/engineering/wire-voltage-drop.json","api":"https://tttkmbb.com/api/v1/calculate/wire-voltage-drop","schema":"https://tttkmbb.com/api/v1/calculators/wire-voltage-drop","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T01:44:51Z"}