Free Construction Calculators & Tools/Cable Sizing Calculator

Cable Sizing Calculator

Determine appropriate cable sizes based on load current, voltage drop limits, and installation conditions. Includes IEC derating factors for temperature, grouping, and installation methods.

Load Parameters
Installation Conditions

Enter load parameters and click Calculate to see cable sizing results

Notes:

  • Calculations based on IEC 60364 / BS 7671 standards
  • BS 7671 guidance (public LV supply): total voltage drop from origin 3% for lighting, 5% for other uses; check the current DEWA/ADDC regulations and project specification
  • XLPE insulation allows higher operating temperature
  • Always verify with local electrical codes and regulations
  • Consider future load growth when selecting cable sizes
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DISCLAIMER

This calculator provides ESTIMATES for preliminary planning purposes. Results are based on standard assumptions and may not reflect your specific project conditions.

By using this tool, you acknowledge that:

1. All calculations are approximate and based on typical industry standards and assumptions.

About This Calculator

The Cable Sizing Calculator helps electrical engineers and MEP contractors determine the correct cable cross-section for power distribution systems across the UAE and Gulf. Calculate required cable sizes based on load current, voltage drop limits, cable length, and installation conditions. Applies IEC/BS derating factors for ambient temperature, cable grouping, and installation methods commonly used in Gulf construction.

When to Use This Calculator

  • Designing electrical distribution systems for buildings
  • Sizing main feeders and sub-main cables
  • Checking voltage drop compliance for long cable runs
  • Applying derating factors for Gulf climate conditions
  • Verifying cable specifications for tender submissions

How to Use This Calculator

1

Enter Load Details

Input load current (A), voltage (V), and power factor for the circuit.

2

Specify Cable Route

Enter cable length and select installation method (tray, conduit, direct burial, etc.).

3

Set Derating Factors

Apply factors for ambient temperature, cable grouping, and installation conditions.

4

Check Voltage Drop

Verify voltage drop is within acceptable limits (typically 3-5% for final circuits).

5

Review Cable Size

Get recommended cable cross-section (mm²) with current-carrying capacity verification.

Typical Scenarios in UAE & Gulf Projects

Commercial Tower in Dubai

An MEP contractor checks the main feeder for an 800A load. The calculator flags that 800A exceeds the largest single cable in its table (300mm²) and gives no breaker size: the feeder needs parallel cables or a busbar trunking system designed by an electrical engineer.

Industrial Facility in Abu Dhabi

A 200A three-phase motor feeder (80m, XLPE, direct in ground, 45°C, 3 grouped circuits). Combined derating is about 0.55, so the calculator selects 300mm² (216A derated) with 0.5% voltage drop and a 200A breaker (Ib ≤ In ≤ Iz).

Calculation Methodology

How Cable Sizing Works

Cable sizing ensures the selected conductor can safely carry the design current without overheating or exceeding voltage drop limits. The fundamental requirement is Iz ≥ Ib ÷ (Ca × Cg × Ci), where Iz is the cable's tabulated current rating, Ib is the design current, and Ca, Cg, Ci are derating factors for ambient temperature, cable grouping, and installation method respectively. The calculator selects the smallest standard cable size (from 1.5 mm² to 300 mm²) whose derated capacity meets or exceeds the design current.

Voltage Drop Calculation

After selecting a cable for current capacity, the voltage drop must be verified. The formula is: Vd(%) = (mV/A/m × Ib × L) ÷ (1000 × V) × 100, where mV/A/m is the cable's voltage drop per ampere per metre (from IEC tables), Ib is the design current in amps, L is the one-way cable length in metres, and V is the system voltage. Per DEWA and ADDC regulations, voltage drop must not exceed 3% for main feeders, 2.5% for sub-mains, and 5% total from transformer to final outlet. If the drop exceeds limits, the calculator automatically upsizes the cable.

Understanding Derating Factors for Gulf Conditions

Standard cable ratings assume 30°C ambient temperature, a single circuit, and open installation. Gulf construction rarely matches these ideal conditions. The ambient temperature factor (Ca) reduces capacity for the 40–50°C temperatures common in UAE — for example, a PVC cable at 45°C is derated to 79% of its standard rating. The grouping factor (Cg) accounts for reduced heat dissipation when multiple cables share a tray or conduit — three grouped cables retain only 70% of individual capacity. The installation method factor (Ci) reflects whether the cable is clipped to a surface (factor 1.0), in conduit (0.87), or buried in a duct (0.80). All three factors multiply together to determine the effective current-carrying capacity.

Frequently Asked Questions

BS 7671 (Appendix 4) and IEC 60364-5-52 give guidance for installations supplied from a public low-voltage network: a total voltage drop from the origin of the installation to the point of use of no more than 3% for lighting and 5% for other uses (6% and 8% where the installation has its own private LV supply). How that total is split between feeders, sub-mains and final circuits is a design choice. Check the current DEWA or ADDC/ADWEA regulations and the project specification, which may set their own limits.

Standard cable ratings are at 30°C ambient. For Gulf conditions (40-50°C), apply derating factors: at 40°C = 0.87, at 45°C = 0.79, at 50°C = 0.71. Example: A 95mm² cable rated 200A at 30°C becomes 174A at 40°C (200 × 0.87).

Aluminum cables are cost-effective for larger sizes (>50mm²) and long runs. Common in main feeders and outdoor installations. Requires larger cross-section than copper (typically 1.6× area for same current). Use copper for final circuits, motor connections, and where space is limited.

For a 32A circuit at 30°C with PVC insulation clipped direct (Method C): 4mm² copper cable is rated at 36A, sufficient for 32A. However, if the cable is in conduit (Method B1, rated 30A at 4mm²), you need to upsize to 6mm² (rated 38A). Always check derating for ambient temperature — in UAE at 40°C, 4mm² drops to ~31A, which is marginal for 32A. A 6mm² cable is the safer choice for Gulf conditions.

For three-phase circuits, voltage drop is: Vd(%) = (mV/A/m × Ib × L) ÷ (1000 × VL) × 100, where VL is the line-to-line voltage (e.g., 400V). The mV/A/m values for three-phase are lower than single-phase because current returns via three conductors. For example, a 50mm² copper cable has 0.93 mV/A/m (three-phase) vs 1.55 mV/A/m (single-phase). A 200A load over 80m on 50mm² at 400V gives: (0.93 × 200 × 80) ÷ (1000 × 400) × 100 = 3.72%. That uses most of a 5% total budget in the feeder alone, so upsizing to 70mm² is usually worthwhile.

The standard copper cable sizes per IEC 60228 used in UAE projects are: 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, and 300 mm². For final circuits, 2.5mm² (lighting) and 4mm² (power sockets) are most common. Sub-mains typically range from 16–70mm², and main feeders from 95–300mm². For loads exceeding 300mm² capacity, parallel cables are used. DEWA and ADDC accept both single-core and multi-core configurations.

PVC (polyvinyl chloride) insulation is rated to 70°C conductor temperature, while XLPE (cross-linked polyethylene) is rated to 90°C. This means XLPE cables carry approximately 15–20% more current for the same cross-section. For example, a 50mm² PVC cable in Method C carries 125A, while the same size in XLPE carries 149A. XLPE also has better resistance to moisture, chemicals, and ageing — making it preferred for underground installations, outdoor cable trays, and Gulf climate conditions where higher ambient temperatures reduce PVC cable ratings more severely.

Both DEWA (Dubai) and ADDC (Abu Dhabi) follow IEC 60364 as the base standard, but have local variations. Voltage drop limits, conductor material rules and approved installation methods can differ between the two authorities and between editions of their regulations, so take the limits from the current DEWA or ADDC/ADWEA regulations and the project specification rather than from this page. Cable colour coding follows the IEC convention: brown/black/grey for phases, blue for neutral, green-yellow for earth. Always verify current edition of the relevant authority's regulations as requirements are updated periodically.

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This calculator reflects the logic built into Arkan's construction management platform.

Last Updated: January 2026

Standards Reference: Calculations based on IEC 60364 and BS 7671 (IET Wiring Regulations)

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