Meter first when possible
Measured phase current avoids the conversion assumptions needed for kW and kVA planning modes and captures whatever mixed load topology already exists.
Best input
3-Phase PDU / Phase Load Balance Calculator
Check whether phase A, B, and C are reasonably balanced, how close the heaviest phase is to its limit, and how much single-phase load you would need to move to rebalance the distribution. Use measured amps when available, or plan from per-phase kW or kVA on common wye systems.
Calculator
Inputs
For kW and kVA modes, this page assumes per-phase line-to-neutral loading on a wye system. If you have mixed line-to-line loads or metered phase currents already, use amperes mode.
Neutral current is estimated from the fundamental current vector only. Harmonic-heavy IT loads can raise neutral current above this estimate.
Results
Highest phase-
Average phase current-
Imbalance-
Estimated neutral current-
Total apparent power-
Total real power-
Enter three phase loads to compare utilization, headroom, and balance.
| Phase | Input | Current | kVA | kW | Target headroom | Utilization | Status |
|---|---|---|---|---|---|---|---|
| No calculation yet. | |||||||
Balancing guidance
Move from highest to lowest-
Lightest phase for new load-
Spread between max and min-
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Assumptions and formulas
The calculator is designed for three-phase distribution review where you already know, or can estimate, the total single-phase load assigned to each phase. It does not attempt to reconstruct phase current from arbitrary line-to-line branch combinations because those currents do not add arithmetically in the simple way many spreadsheets assume.
Wye voltage conversion
V_LN = V_LL / sqrt(3)
Phase current conversion
I_phase = P_phase x 1000 / (V_LN x PF) for kW mode
I_phase = S_phase x 1000 / V_LN for kVA mode
NEMA-style current unbalance
I_avg = (I_A + I_B + I_C) / 3
Unbalance % = 100 x max(|I_A - I_avg|, |I_B - I_avg|, |I_C - I_avg|) / I_avg
Fundamental neutral current estimate
I_N = sqrt(I_A^2 + I_B^2 + I_C^2 - I_A I_B - I_B I_C - I_C I_A)
Schneider Electric documents both the NEMA-style max-deviation imbalance formula and the fact that harmonic-rich nonlinear loads can produce neutral current above the phase current even when the phase fundamentals are balanced. That is why the neutral result here is labeled as a planning estimate rather than a compliance value.
What this is good for
Use this page to compare metered phase currents across rack PDUs, floor PDUs, or panel-fed IT loads; to estimate whether a planned move would improve or worsen balance; and to translate between phase current and per-phase power on common 208Y/120 V, 400Y/230 V, 415Y/240 V, 480Y/277 V, or 600Y/347 V systems.
Do not use it as a substitute for harmonic analysis, branch-circuit coordination, breaker trip studies, or vendor validation for delta systems or unusual line-to-line loading patterns. If you have a smart PDU or meter, measured phase currents remain the strongest input.
Frequently asked questions
What imbalance percentage is acceptable?
There is no universal answer. Many operators treat low-single-digit to around 10% current imbalance as a practical planning target, but the real limit depends on the equipment, neutral loading, upstream transformer effects, and site policy.
Why does the calculator ask for power factor?
Power factor is only needed when you enter kW. Measured amperes and kVA already reflect apparent load directly, so the page uses power factor only to convert between real power and current.
Can I use this for 208 V line-to-line branch loads?
Only indirectly. If those loads are already metered into phase currents, use amps mode. For planning with mixed line-to-line circuits, calculate or meter the resulting phase currents first instead of assuming each branch simply adds to one phase.
Why can neutral current still be high when the phases look balanced?
Switch-mode power supplies and other nonlinear loads can produce triplen harmonics that add in the neutral. The neutral estimate shown here ignores that harmonic component, so it should not be used as a neutral-conductor design check.
Does the 80% continuous target always apply?
No. It is a common planning convention and often lines up with continuous-load practice, but you still need to confirm the actual breaker, cord, PDU, and local code requirements that apply to your installation.
Practical planning notes
Balance protects headroom
One overloaded phase can trip or force derating even if the total three-phase kW still looks comfortable on paper.
Weakest phase wins
Neutral current is not solved by averages
A perfectly even average does not guarantee a lightly loaded neutral once nonlinear IT loads and harmonics enter the picture.
Harmonics matter
Small moves can fix ugly spreads
Shifting one or two single-phase devices from the heaviest phase to the lightest phase can often recover more headroom than expected.
Quick win
Nameplate current is not measured current
Rack drawings and equipment labels are useful starting points, but live metering usually reveals a different operating balance than installed-nameplate totals suggest.
Reality check