Electrical
Voltage drop calculator
Your inputs
Complete only the fields for your selected method. Use one consistent job or reporting period. Use zero for a known zero amount only when the field permits it. Missing costs and market rates are not added automatically. Currency selection labels amounts; it does not convert exchange rates.
How this calculation works
loop resistance = 2 × one-way length × resistance per 1,000 ft / 1,000; drop = current × loop resistance; drop percent = 100 × drop / source voltage
Use a steady direct-current or purely resistive model as described. This estimates electrical quantities only. Use equipment data for the actual operating condition and have a qualified person verify conductor sizing, circuit protection and compliance. Assumes a two-wire circuit with equal outgoing and return conductors. It excludes contact resistance, reactive effects and three-phase configurations. Use your own records for the same scope and period. Example figures are illustrative, not industry benchmarks. Results exclude income taxes and any cost you have not entered. Check the result before pricing work or committing resources.
What information do I need?
Use records for the same job, equipment or accounting period. Only the fields for your selected entry method are required. An unknown amount is not zero.
Input definitions and where to find them
- Source voltage (V): Use the matching measured quantity, time log, schedule or clearly stated estimate. Zero means intentionally none; an unknown amount is not zero.
- Load current at the condition being compared (A): Use the matching measured quantity, time log, schedule or clearly stated estimate. Zero means intentionally none; an unknown amount is not zero.
- One-way wire length (ft): Use the matching measured quantity, time log, schedule or clearly stated estimate. Zero means intentionally none; an unknown amount is not zero.
- Resistance of one conductor at operating temperature (Ω/1,000 ft): Use the matching measured quantity, time log, schedule or clearly stated estimate. Zero means intentionally none; an unknown amount is not zero.
Use the Where to find this value controls beside the inputs for available work-it-out helpers. Estimates remain your assumptions; a helper does not verify the source figures.
Worked example
Example amounts use US dollars (USD).
Example answer: Voltage drop is 2.5250 V for the illustrative inputs below.
Example inputs
- Source voltage: 24.00 V
- Load current at the condition being compared: 5.00 A
- One-way wire length: 100.00 ft
- Resistance of one conductor at operating temperature: 2.525 Ω/1,000 ft
- Voltage drop
- 2.5250 V
- Voltage drop percentage
- 10.5208 %
- Modeled receiving-end voltage
- 21.4750 V
- Round-trip wire resistance
- 0.5050 Ω
- Wire power loss
- 12.6250 W
These illustrative values are not recommended rates or industry averages. Replace every example input with your own figures.
Use the result well
Inputs come from your own records and stated assumptions; no rates or legal limits are looked up.
Review the entered assumptions and calculator limits before using these results. Have a qualified professional verify design and safety decisions.