Calculator Inputs
Example Data Table
| System | Material | Size | Length (m) | Current (A) | Voltage (V) | Drop (V) | Drop (%) | Comment |
|---|---|---|---|---|---|---|---|---|
| Single Phase AC | Copper | 8 AWG | 30 | 40 | 230 | 4.91 | 2.13 | Acceptable branch run |
| Three Phase AC | Aluminum | 25 mm² | 70 | 60 | 400 | 9.88 | 2.47 | Good feeder performance |
| DC | Copper | 16 mm² | 20 | 55 | 48 | 2.73 | 5.69 | Upsize conductor advised |
Formula Used
Temperature-adjusted resistivity:
ρT = ρ20 × [1 + α × (T - 20)]
Resistance of one conductor over one-way length:
R = ρT × L / A
DC circuits:
Vdrop = 2 × I × R
Single-phase AC circuits:
Vdrop = 2 × I × (R × cosφ + X × sinφ)
Three-phase AC circuits:
Vdrop = √3 × I × (R × cosφ + X × sinφ)
Percentage drop: Vdrop% = (Vdrop / Source Voltage) × 100
Here, I is current, L is one-way conductor length, A is effective cross-sectional area, ρ is material resistivity, α is the temperature coefficient, φ is the load angle, and X is conductor reactance.
How to Use This Calculator
- Select the circuit type: DC, single-phase AC, or three-phase AC.
- Choose the conductor material and size method.
- Enter one-way wire length, design current, and source voltage.
- For AC systems, enter power factor and conductor reactance.
- Set conductor operating temperature and number of parallel conductors.
- Enter the maximum acceptable voltage drop percentage.
- Click Calculate Voltage Drop to see results above the form.
- Use the CSV or PDF buttons to export the current result set.
Frequently Asked Questions
1. Why does the calculator ask for one-way length?
One-way length is the physical route from source to load. The calculator automatically applies the return path for DC and single-phase circuits inside the formula.
2. Why does temperature affect voltage drop?
Conductor resistance rises as temperature increases. Higher resistance causes more voltage drop and greater power loss under the same current.
3. When should I include reactance?
Include reactance for AC circuits, especially longer runs, larger conductors, grouped cables, or three-phase feeders. It matters less on short, low-current branch circuits.
4. What is a good design limit for voltage drop?
Many designers target around 3% for branch circuits and around 5% total feeder plus branch drop. Project standards and local codes may differ.
5. How do parallel conductors change the result?
Parallel conductors increase effective cross-sectional area and reduce total resistance. That lowers voltage drop and power loss when current splits evenly between them.
6. Why is aluminum different from copper?
Aluminum has higher resistivity than copper, so it usually needs a larger cross-sectional area to achieve a similar voltage drop at the same load.
7. Does low power factor increase AC voltage drop?
Yes. Lower power factor increases the reactive component in AC calculations, which can raise total voltage drop when conductor reactance is included.
8. Can I use this tool for code compliance decisions?
Use it for design screening and quick checks. Final compliance should always be verified against applicable electrical codes, manufacturer data, and project specifications.