How to Calculate Cable Current Capacity (KHA) and Choose the Right Wire Size

Choosing the correct cable size is one of the most important steps in any electrical installation. Using an undersized cable can cause overheating, voltage drop, and even fire hazards.

In this article, I share my simple and practical method to calculate current carrying capacity (KHA) and determine the proper cable cross-section based on electrical load. This is the same approach I personally use in real projects.

What Is KHA (Current Carrying Capacity)?

KHA refers to the maximum electrical current a cable can safely carry without excessive temperature rise.

Every cable has its limit. If the load current exceeds this limit, insulation damage and safety risks may occur. That’s why calculating KHA before choosing a wire size is essential.

Step 1 – Calculate Load Current

First, calculate the load current (I).

For Single-Phase Systems

I = P / (V × cos φ)

I = Current (Ampere)
P = Power (Watt)
V = Voltage (Volt)
cos φ = Power factor (typically 0.8–0.85)

For Three-Phase Systems

I = P / (√3 × V × cos φ)

Step 2 – Apply Safety Factor (My Simple Trick)

After obtaining the load current, multiply it by 125%.

This provides a safety margin and prevents the cable from operating at its maximum capacity.

Formula:

KHA = 1.25 × I

This is my main trick — simple but effective.

Example Calculation

Power = 2200 W
Voltage = 220 V
Power factor = 0.85

Calculate Current

I = 2200 / (220 × 0.85)
I ≈ 11.7 A

Apply Safety Factor

KHA = 1.25 × 11.7 ≈ 14.6 A

KHA ≈ 15 A

Step 3 – Select Cable Size

1.5 mm² → ~15 A
2.5 mm² → ~20–25 A
4 mm² → ~30–35 A

Recommended cable size:

1.5 mm²

If the cable length is long or ambient temperature is high, choose one size larger.

Why This Method Works

Simple and practical
Includes safety margin
Prevents overheating
Easy to apply
Suitable for residential and small industrial systems

Final Thoughts

Never guess cable size — always calculate.

Calculate load current
Multiply by 125%
Match with cable ampacity table
Increase one size if necessary

Simple. Safe. Practical.