Aisha K.
Mar 12, 2026
Clean layout and the results update instantly. Exactly what I needed for a quick planning check.
Electrical & Wiring
Electrical Voltage Drop Calculator
V_drop = 2 × I × R × length; % = V_drop ÷ system voltage.
Compute voltage drop and percent loss for a circuit run. Planning estimates only — verify measurements and local codes on site.
Inputs
1200
5500
110480
142
Smart analysis
Recommendations
Tailored to your live inputs and result—guidance only, not professional advice.
- Interpret
Treat this as a planning estimate
Primary result: Voltage drop = 5.02 V. Re-run with optimistic and pessimistic inputs to understand the range—not just a single point.
Scenario studio
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Scenario A
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Scenario B
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Plain-English guide
Terms & how it works
Confused by a field? Read the short definitions here while you use the tool.
Load (amps)
The “Load (amps)” value used in this tool’s formula. Adjust it to see results update live.
One-way length (ft)
The “One-way length (ft)” value used in this tool’s formula. Adjust it to see results update live.
System voltage (V)
The “System voltage (V)” value used in this tool’s formula. Adjust it to see results update live.
Wire gauge (AWG number: 14=14, 12=12…)
The “Wire gauge (AWG number: 14=14, 12=12…)” value used in this tool’s formula. Adjust it to see results update live.
How this calculator works
Compute voltage drop and percent loss for a circuit run. Planning estimates only — verify measurements and local codes on site. V_drop = 2 × I × R × length; % = V_drop ÷ system voltage. Example: 40 A on 100 ft with 8 AWG at 240 V → check if under 3% guideline.
V_drop = 2 × I × R × length; % = V_drop ÷ system voltage.
Example: 40 A on 100 ft with 8 AWG at 240 V → check if under 3% guideline.
When to use this Voltage Drop
Common use cases
- Compute voltage drop and percent loss for a circuit run.
- Sanity-check with this case: 40 A on 100 ft with 8 AWG at 240 V → check if under 3% guideline.
- The relationship is: V_drop = 2 × I × R × length; % = V_drop ÷ system voltage.
Localized examples
- Electrical & Wiring: the example on this page uses the same formula as the widget.
What you get
- Fields: Load (amps), One-way length (ft), System voltage (V), Wire gauge (AWG number: 14=14, 12=12…)
- V_drop = 2 × I × R × length; % = V_drop ÷ system voltage.
- Example on the page: 40 A on 100 ft with 8 AWG at 240 V → check if under 3% guideline.
How to Calculate Voltage Drop Step-by-Step
- 1Enter Load (amps), One-way length (ft), System voltage (V), then the remaining fields. Use the values you have, not a catalog average, unless that is all you know.
- 2V_drop = 2 × I × R × length; % = V_drop ÷ system voltage.
- 3Worked case: 40 A on 100 ft with 8 AWG at 240 V → check if under 3% guideline.
- 4Buy materials after you walk the job. This is a first-pass quantity, not a purchase order.
Governing formula
V_drop = 2 × I × R × length; % = V_drop ÷ system voltage.
40 A on 100 ft with 8 AWG at 240 V → check if under 3% guideline.
Example: set Load (amps) = 40, One-way length (ft) = 100, System voltage (V) = 240, then read the result.
Variable definitions
- loadAmps
Load (amps)
The “Load (amps)” field. Default 40; typical range 1–200.
- lengthFt
One-way length (ft)
The “One-way length (ft)” field. Default 100; typical range 5–500.
- voltage
System voltage (V)
The “System voltage (V)” field. Default 240; typical range 110–480.
- wireGaugeAwG
Wire gauge (AWG number: 14=14, 12=12…)
The “Wire gauge (AWG number: 14=14, 12=12…)” field. Default 8; typical range 14–2.
- The takeoff (V_drop = 2 × I × R × length; % = V_drop ÷ system voltage.) ignores waste, code, and what you find when you open the wall. Measure twice on site.
- Nothing here is uploaded for the calculation itself.
Frequently Asked Questions
V_drop = 2 × I × R × length; % = V_drop ÷ system voltage.
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Community
Reviews & Ratings
See what others think about this tool, then leave your own rating to help improve CalculioHub.
4.8
out of 5.0
4 reviews
Daniel R.
Feb 28, 2026
Very usable on mobile. Would love a save/export option later, but the math feels solid.
Priya S.
Feb 3, 2026
The FAQ section answered my questions before I even had to search. Smooth dark mode too.
Marcus L.
Jan 19, 2026
Simple inputs, clear outputs. This replaced three bookmarks I used to juggle.
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