Amps to kVA converter
Converting amps to kVA finds the apparent power that a current represents at a given voltage, the figure used to compare a load with the kVA rating of a transformer, generator or UPS. Because kVA counts all the current the source must supply, no power factor is applied.
Convert amps to kVA
Updates as the values change. The page address keeps the values for sharing.
NEC load calculations under Article 220 are carried out in volt-amperes, and panel schedules total their loads in VA. Converting a feeder current or a calculated load in amps to kVA connects those figures with the equipment that will supply them.
Formulas
Single phase AC
On a 120/240 V system the 240 V value is used with the current on each leg; a balanced 100 A load is 24 kVA.
Three phase AC
Gives the total apparent power of a balanced three-phase load from the current in one line, for comparison with a three-phase transformer's nameplate.
The result is kVA and, alongside it, VA. Converting further to kW requires the load's power factor; the kVA to kW converter does that step.
Worked examples
150 A of calculated load at 208 V three phase
The demand load of a small commercial space, from its load calculation.
kVA = √3 × V(L-L) × I ÷ 1,000kVA = 1.732 × 208 V × 150 A ÷ 1,000 = 54.04 kVA
The load is 54.0 kVA. The transformer chosen is the next standard rating at or above that figure, with any allowance for growth decided by the designer.
80 A on a 240 V single-phase circuit to a UPS
The current drawn at full load by the equipment the UPS will carry.
kVA = V × I ÷ 1,000kVA = 240 V × 80 A ÷ 1,000 = 19.2 kVA
The load is 19.2 kVA, the figure to compare with the UPS kVA rating; its kW rating is checked separately against the load's real power.
400 A at 480 V three phase
A main feeder current on a 480Y/277 V service.
kVA = √3 × V(L-L) × I ÷ 1,000kVA = 1.732 × 480 V × 400 A ÷ 1,000 = 332.554 kVA
The apparent power is 332.6 kVA.
Conversion table
| Amps (A) | 120 V single phase (kVA) | 240 V single phase (kVA) | 208 V three phase (kVA) | 480 V three phase (kVA) |
|---|---|---|---|---|
| 10 | 1.20 | 2.40 | 3.60 | 8.31 |
| 15 | 1.80 | 3.60 | 5.40 | 12.47 |
| 20 | 2.40 | 4.80 | 7.21 | 16.63 |
| 30 | 3.60 | 7.20 | 10.81 | 24.94 |
| 40 | 4.80 | 9.60 | 14.41 | 33.26 |
| 50 | 6.00 | 12.00 | 18.01 | 41.57 |
| 60 | 7.20 | 14.40 | 21.62 | 49.88 |
| 80 | 9.60 | 19.20 | 28.82 | 66.51 |
| 100 | 12.00 | 24.00 | 36.03 | 83.14 |
| 125 | 15.00 | 30.00 | 45.03 | 103.92 |
| 150 | 18.00 | 36.00 | 54.04 | 124.71 |
| 200 | 24.00 | 48.00 | 72.05 | 166.28 |
| 225 | 27.00 | 54.00 | 81.06 | 187.06 |
| 300 | 36.00 | 72.00 | 108.08 | 249.42 |
| 400 | 48.00 | 96.00 | 144.11 | 332.55 |
| 600 | 72.00 | 144.00 | 216.16 | 498.83 |
| 800 | 96.00 | 192.00 | 288.21 | 665.11 |
Generated by the converter's engine. Each column applies to a system of that voltage and phase only.
Common mistakes
Choosing a generator by kW when the load is given in kVA
A generator rated 100 kW at PF 0.8 supplies 125 kVA. Comparing a load's kVA with the generator's kW rating, or the reverse, can make the unit look larger or smaller than it is.
Using the single-phase formula on a three-phase load
Leaving out √3 for a three-phase load gives only 58% of its true apparent power, enough to undersize a transformer by nearly half.
Treating 120 V as the line-to-line voltage of a 208Y/120 V system
On a 208Y/120 V system, 120 V is phase to neutral. Used in the three-phase formula as if it were line to line, it understates the kVA by 42%.
Converting a breaker rating instead of the load
A 200 A main breaker converts to a kVA figure for the panel's capacity, which is not the demand load the transformer must serve. The load calculation gives the current to convert.
Frequently asked questions
How many kVA is 100 amps at 208 V three phase?
36.03 kVA. At 480 V three phase, 100 A is 83.14 kVA.
How many kVA is 100 amps at 240 V single phase?
24.0 kVA; at 120 V it is 12.0 kVA.
Why do NEC load calculations use VA instead of watts?
Conductors and transformers must carry the full current, including the reactive part. Working in volt-amperes keeps the calculation tied to current, whatever the power factor of the loads.
What kVA is a 200 A residential service?
At 240 V a 200 A service corresponds to 48.0 kVA at full rating. Utility transformers serving homes are sized from diversified demand, which is usually much lower.
How is kVA converted to kW?
By multiplying by the power factor: kW = kVA × PF. A 50 kVA load at PF 0.9 is 45 kW. The kVA to kW converter shows the reactive power as well.