Distribution Transformer Load Calculator
Enter your transformer rating, connected load and power factor to find the loading percentage, spare kVA capacity and rated 3-phase current, with a clear load status and recommendation.
Results
Load (kVA)
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Loading
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Spare capacity (kVA)
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Rated current (A)
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Load current (A)
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Status
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Current values are calculated for a 3-phase transformer at 400 V line voltage: current (A) = kVA x 1000 / (1.732 x 400).
How to use
- Enter the transformer nameplate rating in kVA (for example 50, 100 or 200).
- Enter the total connected load in kW and the average power factor (0.8 is typical for mixed loads).
- Press Calculate to see loading percentage, spare capacity, currents and the load status.
Understanding the result
- Under-loaded (below 50%) — the transformer is running well below its capacity, which usually means higher relative losses and a larger-than-needed unit.
- Optimal (50% to 90%) — a healthy range with good efficiency and room for short peak loads.
- Near limit (90% to 100%) — acceptable but with little margin; watch for future load growth.
- Overloaded (above 100%) — reduce connected load, shift some load to another transformer, or plan an upgrade before the winding overheats.