What the result means
kVA is apparent power: volts times amps, divided by 1,000, with 1.732 added for three-phase. Transformers, generators and UPS units are rated in kVA because they must carry the full current regardless of power factor.
Use kVA to amps to find how much current a transformer or generator can supply, and amps to kVA to see how much capacity a measured load uses.
How it's calculated
- Single-phase: kVA = V × I ÷ 1,000
- Three-phase: kVA = 1.732 × V × I ÷ 1,000
- I = kVA × 1,000 ÷ (V or 1.732 × V)
Worked example
A 208 V three-phase panel carrying 100 A per phase.
- kVA = 1.732 × 208 × 100 ÷ 1,000
- kVA = 36.03
That load uses 36.03 kVA of transformer or generator capacity.
Reference table
The values below are computed from the same calculator functions used above. They let you compare common sizes and operating points without replacing the interactive calculation or its assumptions.
| kVA | 208 V | 240 V | 480 V |
|---|---|---|---|
| 15 | 41.64 | 36.09 | 18.04 |
| 30 | 83.27 | 72.17 | 36.09 |
| 45 | 124.91 | 108.26 | 54.13 |
| 75 | 208.19 | 180.43 | 90.21 |
| 100 | 277.58 | 240.57 | 120.28 |
| 112.5 | 312.28 | 270.64 | 135.32 |
| 150 | 416.37 | 360.85 | 180.43 |
| 225 | 624.56 | 541.28 | 270.64 |
| 300 | 832.74 | 721.71 | 360.85 |
| 500 | 1387.90 | 1202.85 | 601.42 |
Reference values are examples based on the stated assumptions. Verify manufacturer data, conductor ampacity and local requirements before using a result.
Sources and assumptions
The listed formulas use the assumptions shown in the worked example. Calculator formulas are published with their units so a technician can check a result instead of treating it as a black box.
Last reviewed . Spot an error? Email support@tiermenu.com.
FAQ
What's the difference between kVA and kW?
kW = kVA × power factor. kVA is what equipment must carry, kW is the work done.
How many amps is a 75 kVA transformer at 208 V three-phase?
75,000 ÷ (1.732 × 208) ≈ 208 A full-load on the secondary.
Does single-phase 240 V use 1.732?
No. Standard 120/240 V split-phase is single-phase, so kVA = V × I ÷ 1,000.
Is 208 V single-phase from a three-phase panel single-phase?
Yes, a two-pole load on 208 V is a single-phase load. Use the single-phase mode with 208 V.
Using a reference result in the field
A calculator is most useful when the inputs match the job being checked. Where a field asks for a length, confirm whether it is one-way or total; where it asks for current, confirm whether the load is continuous or intermittent. The unit label beside the result is part of the result; do not carry a number into another calculation without checking its units.
Reference rows are provided for comparison, not as universal design limits. They use the values and conditions stated with each table. A different conductor material, temperature, power factor or load type can change a field result. Where the page calls out a code check, equipment rating or manufacturer table, that check remains part of the job.
Use the interactive inputs for the exact conditions at hand, then review the displayed formula and assumptions. If a value looks unexpected, change one input at a time and compare it with a known point in the reference table. Keep the measured readings and job-specific notes with the work record so another technician can understand how the result was obtained.
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