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Voltage Drop Calculator

Science & Engineering

Single/three-phase · wire sizing · 5% rule

Quick Answer

Voltage Drop Calculator: Single/three-phase · wire sizing · 5% rule. Voltage Drop Calculator uses standard science & engineering formulas to compute accurate results instantly.

V
A
m
Voltage drop
6.72 V · 3.05%
Good (≤4%)

All sizes comparison

SizeΔV%
1.5 mm²11.20 V5.09%
2.5 mm²6.72 V3.05%
4 mm²4.20 V1.91%
6 mm²2.80 V1.27%
10 mm²1.68 V0.76%
16 mm²1.05 V0.48%
25 mm²0.67 V0.31%
35 mm²0.48 V0.22%
50 mm²0.34 V0.15%
70 mm²0.24 V0.11%
95 mm²0.18 V0.08%
Rule of thumb: keep drop ≤ 5% for lighting circuits (GB code) and ≤ 8% for motors at start. Single-phase current flows out AND back — hence the factor 2; balanced three-phase uses √3. Resistivity at 20°C: copper 0.0175, aluminum 0.0283 Ω·mm²/m; both rise ~0.4%/°C with temperature.

Calculation steps

  1. 1ΔV = 2·ρ·L·I/S = 2.000 × 0.0175 × 30 × 16 / 2.5 = 6.72 V
  2. 2Percentage = ΔV/U = 6.72/220 = 3.05%

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How to Use

  1. Enter known quantities: fill values and confirm units in the Voltage Drop Calculator.
  2. Instant solution: unknowns solve live with the formula shown transparently.
  3. Use constant/material tables: standard physical constants and material data are listed on this page.
  4. Compare conditions: change inputs to compare scenarios.

Key Points

  • Voltage Drop Calculator is a free online science & engineering tool — open and use, no sign-up.
  • All calculations run locally in your browser; your data never leaves the device.
  • Key capability: Single/three-phase · wire sizing · 5% rule.
  • Results come with formulas and reference tables so you can verify every number.

Formula & How It Works

Voltage Drop Calculator formula

Voltage Drop Calculator uses standard science & engineering formulas to compute accurate results instantly.

FAQ

How do I use the Voltage Drop Calculator?
Open the page and fill in the input fields — results update automatically. Single/three-phase · wire sizing · 5% rule.
Are the results accurate?
Yes. Standard formulas and conversion factors are used and verified.
Is it free? Do I need to sign up?
Completely free. No registration, login or download required.
Does it work on mobile?
Yes. The responsive design works on phones, tablets and desktops.
Is my data saved?
No. Everything runs locally in your browser.

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Source & Updates

Based on CODATA recommended constants and standard physics formulas. Last updated: 2025-07

Last updated:

Formulas and content on this page are reviewed by the YiJianSuan team. For reference only — official sources prevail.

Maintained and periodically reviewed by the YiJianSuan editorial team — review process in ourEditorial Policy.

Cite this page: YiJianSuan. Voltage Drop Calculator[EB/OL]. https://www.yijiansuan.com/en/c/science/voltage-drop

Results provided by this tool are for reference only and do not constitute professional advice.