Three-Phase Current Calculator
Three-phase power calculations need a √3 factor that trips people up if they're used to single-phase math — this handles that directly from power, line voltage and power factor.
Inputs
Result
24.55 A
I = P / (√3 × V × pf)
How the three-phase current calculator works
Line current: I = P ÷ (√3 × V × power factor), where P is in watts, V is line-to-line voltage.
The √3 (≈1.732) accounts for the phase relationship between the three conductors in a balanced three-phase system.
Worked example: 15 kW load, 415 V line voltage, 0.85 power factor
- I = (15 × 1000) ÷ (1.732 × 415 × 0.85) = 15,000 ÷ 611.3 ≈ 24.54 A.
Common mistakes to avoid
Applying the single-phase formula (I = P ÷ V) to a three-phase system
Skipping the √3 factor overstates the current by roughly 73%, since three-phase power delivers the same total power at a lower current per conductor than single-phase would for the same voltage.
Using phase voltage instead of line voltage, or vice versa
Line-to-line voltage (between any two of the three phases) and line-to-neutral voltage are different values in a three-phase system — mixing them up throws off the result by a factor of √3 in the wrong direction.
Frequently asked questions
Why is three-phase power used for larger industrial loads?
It delivers the same total power at lower current per conductor than single-phase, meaning thinner cables and smaller equipment for a given power rating — a major cost saving at scale.
What's the relationship between line voltage and phase voltage?
In a standard three-phase system, line voltage = phase voltage × √3 — for example, 230 V phase voltage corresponds to about 400 V line voltage.
Does power factor affect three-phase systems the same way it affects single-phase?
Yes, the same underlying concept applies — a lower power factor increases the current needed to deliver the same real power, in both single and three-phase systems.
How would this change for an unbalanced three-phase load?
This formula assumes a balanced load across all three phases; an unbalanced load needs each phase's current calculated separately, since they'd draw different amounts.
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