Complete guide
Voltage Drop Calculator: formula, worked example and interpretation
Estimate conductor voltage drop from current, one-way length, resistance per thousand feet and circuit type. Enter the known values and the result updates instantly with an auditable breakdown.
What the Voltage Drop Calculator answers
Estimate conductor voltage drop from current, one-way length, resistance per thousand feet and circuit type.
Use the breakdown to compare the result with the source values before making a decision.
Formula and variables
The calculation uses drop=K×current×resistance×length/1000; K=2 for two-wire or √3 for three-phase. Every variable comes directly from a labeled field.
drop=K×current×resistance×length/1000; K=2 for two-wire or √3 for three-phaseWorked example
A 120 V, 15 A load across 100 ft with 1.588 ohm/1,000 ft drops about 4.76 V in a two-wire circuit.
Changing any field recalculates the result immediately, so nearby scenarios can be compared without reloading the page.
How to use the result
Treat the result as a planning value and compare it with the detailed rows shown beside it.
Keep units and time periods consistent. Use the share or PDF action to preserve the exact assumptions.
Assumptions and scope
This screening estimate omits reactance, temperature, power factor, terminals and code requirements; final conductor sizing needs applicable electrical rules.
The calculator exposes its assumptions instead of filling missing facts with hidden estimates.
Accuracy checks
Confirm the units, dates, rates and source figures before relying on the output.
Round only the displayed answer; Calculator24 keeps full JavaScript precision for intermediate arithmetic and exported values.
Input and output checklist
| Item | What to enter or review |
|---|---|
| Inputs | Source voltage (V), Load current (A), One-way conductor length (ft), Conductor resistance (ohm/1,000 ft), Circuit |
| Equation | drop=K×current×resistance×length/1000; K=2 for two-wire or √3 for three-phase |
| Example | A 120 V, 15 A load across 100 ft with 1.588 ohm/1,000 ft drops about 4.76 V in a two-wire circuit. |
| Limit | This screening estimate omits reactance, temperature, power factor, terminals and code requirements; final conductor sizing needs applicable electrical rules. |
Frequently asked questions
What does this Voltage Drop Calculator calculate?
Estimate conductor voltage drop from current, one-way length, resistance per thousand feet and circuit type.
Which formula does it use?
drop=K×current×resistance×length/1000; K=2 for two-wire or √3 for three-phase
Does the result update while I type?
Yes. Valid changes recalculate after a short delay and the previous result is not substituted for invalid input.
Which assumptions should I check?
Check units, rates, dates and every source value shown in the form.
Is the result exact?
This screening estimate omits reactance, temperature, power factor, terminals and code requirements; final conductor sizing needs applicable electrical rules.
Can I save or share the calculation?
Yes. Copy, Share, WhatsApp, PDF/Print, CSV, comparison and parameterized-link actions are available.
What to keep in mind
This screening estimate omits reactance, temperature, power factor, terminals and code requirements; final conductor sizing needs applicable electrical rules.
Results display up to 8 decimal places; exported numbers preserve calculation precision. This is a calculation summary, not an official certificate.