Reproduce one steady-DC voltage-drop record for a selected 8–18 AWG annealed-copper two-conductor candidate without selecting wire or claiming compliance.
Use this result well
Inputs that matter
One named review scope; current/source basis; responsible review, product, route/temperature and installation-boundary records; one supported 8–18 AWG uncoated annealed-copper candidate; measured one-way route; entered conductor temperature, steady DC current, source voltage and source-owned drop threshold
Output to expect
Temperature-adjusted reference resistance, two-conductor loop resistance, voltage drop and percentage, remaining terminal voltage, entered-threshold margin, ideal constant-current I²R dissipation and an arithmetic within/outside status for that candidate
How it works
Adjust the NIST 20 °C annealed-copper resistance with the entered coefficient relation, double the one-way route for separate outgoing and return conductors, apply ΔV = I × Rloop, and compare the result only with the user-entered threshold
The model is steady DC with a separately established current and an uncoated annealed-copper two-conductor loop. It refuses AC/reactive behavior, shared/chassis returns, other materials, finished-cable selection and code-sizing tasks.
Within the entered threshold is not a wire recommendation or proof of ampacity, protection, temperature, insulation, terminals, fault behavior, product suitability, workmanship, code compliance or installation approval; keep qualified review external.
Choose your path
Built around the job you need to finish
Reproduce one already identified 8–18 AWG uncoated annealed-copper candidate's steady-DC two-conductor voltage-drop record at an entered temperature and compare it only with a source-owned threshold, without selecting wire or approving an installation.
Electrical engineer reviewing one low-voltage DC candidate
Trace the current, source, route, temperature and copper resistance basis instead of accepting a hidden wire-size recommendation.
Name the review record, classify the current/source basis, retain product and safety boundaries, enter one candidate and inspect resistance, drop, margin and I²R arithmetic.
Can reproduce the candidate calculation and route it through product, protection, thermal, fault and installation review without treating arithmetic status as approval.
Technician reconciling a changed route or operating assumption
Update a measured one-way path or planning temperature without silently changing conductor, current, voltage or threshold assumptions.
Load the retained record, change only the reviewed field, confirm the doubled route and adjusted resistance, then retain a new candidate result for the named reviewer.
Produces a versioned, field-transparent result with no automatic conductor substitution or stale hidden assumption.
Safety, code, accessibility or mobile reviewer
Confirm unsupported AC/material/return/code tasks are refused and that every boundary and result remains operable on a narrow screen.
Exercise unsupported model options, required/bounded fields, threshold states, manual history, export, reset, authority links and desktop/mobile layouts.
Finds no unsafe recommendation, duplicate announcement, unnamed control, horizontal overflow or evidence claim beyond the tested surface.
Authoritative checks for this tool
Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.
The selectable gauges use nominal DC resistance for uncoated annealed copper at 20 °C from NBS Handbook 100. A reference-table value is not a certificate for a finished cable, strand construction, plating, terminals or installed route.
R20 = NIST table value in Ω per 1,000 ft
Reproduce the bounded two-conductor model
The engine adjusts reference resistance with the entered 20 °C copper coefficient, doubles one-way length for distinct outgoing and return conductors, then applies steady-current Ohm's-law arithmetic. The entered temperature is an assumption, not a predicted operating temperature.
The page reports whether this candidate's arithmetic is within the threshold copied from the responsible design record. It does not prescribe a universal percentage or evaluate ampacity, overcurrent protection, fault current, insulation, terminals, environment, product suitability, workmanship or code approval.
drop % = ΔV ÷ source V × 100; margin = entered threshold − calculated drop
Updated: August 2026
Example Scenarios
An engineer records the current/source basis, exact candidate status and measured route, then reproduces the 12 AWG drop calculation before completing product, protection and installation review.
A technician updates the one-way route and planning temperature for the same approved calculation basis, retains the new candidate result and returns it to the responsible reviewer rather than selecting a conductor.
A reviewer selects the AC/reactive, shared-return, other-material or code-sizing boundary and receives a task-specific refusal directing the work to the applicable product data and qualified electrical method.
Common Mistakes to Avoid
✕
Treating a passing voltage-drop comparison as a wire-size recommendation
✓
Keep the selected gauge labeled as a candidate and retain separate ampacity, protection, thermal, product, fault, terminal, code and authorization records.
✕
Entering an unreviewed average, nominal voltage or guessed route
✓
Use a source-owned steady-current and source-voltage basis, measure the one-way route, document the planning temperature and return the result to the named responsible reviewer.
FAQ
No. It means only that this candidate's calculated steady-DC drop is not above the percentage you entered. Ampacity, overcurrent protection, temperature rise, insulation, terminals, fault behavior, product suitability, code compliance and authorization require separate evidence and qualified review.
Voltage drop is only one design consideration, and this page does not have the installation, protection, conductor, environment, equipment and jurisdiction evidence needed to select wire. Enter one already identified candidate and review the record responsibly.
Enter the measured source-to-load route once. The supported model doubles it for separate outgoing and return conductors and reports the resulting round-trip length. Do not use this model for a chassis or shared return.
No. The executable boundary is steady DC with uncoated annealed copper and two distinct conductors. AC/reactive behavior, other materials and finished-cable selection require the applicable standards, product records and engineering method.
It adjusts the NIST 20 °C reference resistance using the displayed coefficient relation. The Tool does not predict conductor temperature, thermal equilibrium or insulation suitability; establish and review that temperature basis externally.
About Reviewed Copper Voltage-Drop Candidate
Use this record after the circuit scope, steady current, source voltage, candidate conductor and responsible reviewer are already identified. It applies the NIST annealed-copper resistance basis to one selected 8–18 AWG candidate, adjusts resistance for an entered conductor temperature, doubles the measured one-way route for separate outgoing and return conductors, and compares the calculated drop with a threshold you supply. It does not choose wire, establish current, model AC or shared returns, verify a finished cable, determine ampacity or protection, or approve electrical work.