Voltage Drop Chart
A printable voltage drop chart in PDF: copper and aluminium across 12 wire sizes, 8 run lengths, with NEC 3 % branch and 5 % total limits highlighted. Reviewed by a licensed PE.
Download as PDF
Single A4 page, ~ 80 kB, ready to print or pin in a job folder.
Download PDF (full chart)Need a chart for a specific load and length? Use the interactive voltage drop calculator — it generates a per-circuit PDF.
The chart — Copper, 1-phase 240 V, 20 A
%-drop = (2 × I × R × L) / V × 100 with R from NEC Chapter 9 Table 8 at 75 °C. Bold orange cells exceed 3 %; bold red cells exceed 5 %.
| Length (ft) → | #14 | #12 | #10 | #8 | #6 | #4 | #2 | #1 | 1/0 | 2/0 | 3/0 | 4/0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 25 | 0.64 | 0.40 | 0.25 | 0.16 | 0.10 | 0.06 | 0.04 | 0.03 | 0.03 | 0.02 | 0.02 | 0.01 |
| 50 | 1.28 | 0.80 | 0.50 | 0.32 | 0.20 | 0.13 | 0.08 | 0.06 | 0.05 | 0.04 | 0.03 | 0.03 |
| 75 | 1.92 | 1.21 | 0.76 | 0.48 | 0.31 | 0.19 | 0.12 | 0.10 | 0.08 | 0.06 | 0.05 | 0.04 |
| 100 | 2.56 | 1.61 | 1.01 | 0.64 | 0.41 | 0.26 | 0.16 | 0.13 | 0.10 | 0.08 | 0.06 | 0.05 |
| 150 | 3.84 | 2.41 | 1.51 | 0.96 | 0.61 | 0.39 | 0.24 | 0.19 | 0.15 | 0.12 | 0.10 | 0.08 |
| 200 | 5.12 | 3.22 | 2.02 | 1.27 | 0.82 | 0.51 | 0.32 | 0.26 | 0.20 | 0.16 | 0.13 | 0.10 |
| 250 | 6.40 | 4.02 | 2.52 | 1.59 | 1.02 | 0.64 | 0.40 | 0.32 | 0.25 | 0.20 | 0.16 | 0.13 |
| 300 | 7.68 | 4.83 | 3.03 | 1.91 | 1.23 | 0.77 | 0.49 | 0.39 | 0.31 | 0.24 | 0.19 | 0.15 |
For aluminium, multiply each value by ~ 1.6. Full Cu + Al matrix (12 sizes × 8 lengths) is in the downloadable PDF.
Quick examples
Example 1 — 20 A receptacle on 100 ft of 12 AWG Cu (240 V). Chart shows 1.61 % drop. Code-compliant on the branch (under 3 %).
Example 2 — 20 A on 250 ft of 12 AWG Cu (240 V). Chart shows 4.02 % drop — over 3 %. Upsize to 10 AWG (2.52 %) or accept the drop if total feeder + branch stays under 5 %.
Example 3 — 30 A EV charger on 80 ft of 10 AWG Cu (240 V). Chart at 75 ft × 30 / 20 = 0.76 × 1.5 = 1.14 % at 30 A. Add 5 ft → ~ 1.21 %. Well within 3 %.
Example 4 — 60 A subpanel feeder on 150 ft of 4 AWG Cu (240 V). Chart shows 0.39 % at 20 A → 0.39 × 60 / 20 = 1.17 % at 60 A. Excellent.
- What is the NEC voltage drop limit?
- The NEC does not mandate a voltage drop limit, but the Informational Notes to NEC 210.19(A) (branch circuits) and 215.2(A) (feeders) recommend ≤ 3 % drop on the branch and ≤ 5 % combined feeder + branch for "reasonable efficiency of operation." Some local jurisdictions (and AS/NZS 3000) make these limits enforceable. The chart on this page colour-codes every cell that exceeds 3 % (orange) or 5 % (red) so you can pick a wire size at a glance.
- How do I read a voltage drop chart?
- Find your run length on the left axis and your conductor size on the top. The cell shows the voltage drop as a percentage of the source voltage for the reference load (20 A at 240 V single-phase in this chart). To convert: drop scales linearly with current — at 40 A double the value, at 10 A halve it. Drop in % is inversely proportional to voltage — at 120 V double the percentage, at 480 V quarter it.
- Voltage drop chart for 12V DC and 24V DC systems?
- For low-voltage DC (solar, RV, battery banks), the same physics apply but the percentages are much higher because the system voltage in the denominator is small. 10 AWG copper at 50 ft and 20 A on 12 V DC drops ~ 20 % — totally unusable. Low-voltage DC almost always needs an upsize: use 4 AWG or 2 AWG for any run over 25 ft at 20 A. The interactive voltage drop calculator handles DC mode directly.
- Does the chart work for 3-phase circuits?
- The chart shown here is for single-phase 240 V. For 3-phase use the formula Vd% = (√3 × I × R × L) / V × 100, which gives roughly 13 % less drop than the single-phase chart for the same conductor and length. A 3-phase circuit at 480 V also benefits from a 2× higher denominator, so 3-phase 480 V runs are roughly 4× more forgiving than 1-phase 240 V at the same current.
- When is voltage drop critical?
- Long runs (≥ 100 ft) and motor loads. Motors lose torque proportional to V², so a 10 % drop becomes a 19 % torque loss at start-up — often enough to stall a fully loaded motor or trip the overloads. For lighting, > 3 % drop visibly dims incandescents and reduces LED driver life. For electronics with universal-input switching power supplies, voltage drop matters less but still affects efficiency.
Sources
- NFPA. NFPA 70 — National Electrical Code (2023). Article 210.19(A) Informational Note No. 4 (branch); Article 215.2(A) Informational Note No. 2 (feeder); Chapter 9 Table 8 (DC resistance).
- Standards Australia. AS/NZS 3008.1.1:2017 — Selection of cables — Section 4 (voltage drop).
- IEC. IEC 60364-5-52:2009 Annex G — Voltage drop in consumer installations.