Size aluminum conductors faster with clear ampacity math. Add derating, margins, and continuous load checks. See the recommended gauge and print a report now.
| Scenario | Load (A) | Rating | Ambient (°C) | CCC | Margin | Typical Outcome |
|---|---|---|---|---|---|---|
| Small feeder | 55 | 75°C | 30 | 3 | 10% | Often fits around 6 AWG |
| Warm area | 80 | 75°C | 40 | 3 | 10% | Upsize due to ambient derating |
| Bundled conductors | 120 | 90°C | 35 | 6 | 0% | Upsize due to CCC adjustment |
1) Required design current
Ireq = Iload × (continuous ? 1.25 : 1.00) × (1 + margin%/100)
2) Adjusted ampacity
Iadj = Ibase × Fambient × FCCC
3) Selection rule
Choose the smallest size where Iadj ≥ Ireq
Base ampacity starts from a 30°C reference table for aluminum conductors with up to three current‑carrying conductors. Choose 60°C, 75°C, or 90°C to reflect insulation and termination limits. For example, 4 AWG shows 70 A at 60°C, 85 A at 75°C, and 95 A at 90°C, before any adjustments.
Ambient temperature changes allowable current. This calculator applies a correction factor Fambient relative to 30°C. At 40°C, typical factors are 0.82 (60°C), 0.88 (75°C), and 0.91 (90°C). A 85 A base at 75°C becomes 74.8 A after temperature correction, highlighting why warm spaces often require upsizing.
When more than three conductors share a raceway or cable, heat builds up and the CCC factor reduces ampacity. The tool uses common brackets: 4–6 CCC uses 0.80, 7–9 uses 0.70, and 10–20 uses 0.50. With six CCC, a temperature‑corrected 74.8 A becomes 59.8 A.
Continuous loads typically require 125% sizing. The required design current is Ireq = Iload × 1.25 when selected. If a circuit draws 80 A continuously, the base requirement becomes 100 A. Adding a 10% margin increases the target to 110 A, supporting future expansion and measurement uncertainty.
The results table lists adjusted ampacity Iadj = Ibase × Fambient × FCCC and compares it to Ireq. Utilization is shown as Required ÷ Adjusted. A utilization of 85% means a 15% thermal reserve under these assumptions. The recommended size is the smallest option where Iadj meets or exceeds Ireq.
Use the Plotly chart to compare sizes visually and to communicate decisions. Always confirm conductor type, installation method, termination ratings, and any additional derating rules that apply locally. Export CSV for design records and PDF for job submittals, then keep test readings and as‑built notes with the calculation set. If voltage drop is critical, calculate it separately and always coordinate breaker selection with equipment nameplate limits.
Select the lowest temperature rating that applies to both the conductor insulation and the termination points. If lugs are marked 75°C, treat the circuit as 75°C even when insulation is higher rated.
More current‑carrying conductors in a shared pathway raise heat density. Adjustment factors reduce allowable current to control conductor temperature, which helps prevent insulation damage and premature failures.
Continuous load means the current is expected to run for an extended period. When selected, the calculator applies a 125% sizing factor so the conductor has thermal headroom during long operating intervals.
No. This is a planning estimate based on a reference table and basic derating. You must confirm wiring method, local code, termination ratings, and any additional correction rules before finalizing the design.
It does not calculate voltage drop. If the run is long or the load is sensitive, compute voltage drop separately and upsize conductors or adjust circuit design to meet your performance target.
Use CSV for design logs, peer review, or importing into spreadsheets. Use PDF for submittals, job folders, and client documentation. Keep both with project assumptions and any later field verification notes.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.