Transformer Load Calculator
Actual transformer loading in kVA and percent of rating from measured voltage and current, plus full-load current.
Inputs
kVA
V
A
Results
- Load
- 74.8 %
- Actual load
- 374.1 kVA
- Full-load current
- 721.7 A
- Spare capacity
- 125.9 kVA
Formula
Load kVA = V × I (× √3) ÷ 1000
Load % = Load kVA ÷ Rating × 100
Full-load current = Rating × 1000 ÷ (V × √3)
Assumptions & limits
- Use the highest phase current for unbalanced loads.
- Keep normal loading at or below ~80% for headroom.
Worked example
400 × 540 × 1.732 ÷ 1000 = 374.1 kVA = 74.8% of 500 kVA; full load = 721.7 A.