Amps to kVA Calculator

Convert the amps of a feeder, service or breaker into kVA, the unit UPS, generator and transformer ratings use.

Inputs

Result

Enter the current in amps to see the apparent power in kVA.

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How the calculation works

Apparent power in kVA is volts × amps, with √3 for three-phase:

Single-phase: kVA = volts × amps ÷ 1,000
Three-phase: kVA = √3 × volts × amps per phase ÷ 1,000, with the line-to-line voltage and √3 ≈ 1.732

No power factor is involved. The answer is the capacity of the conductors or breaker in the same unit that UPS, generator and transformer nameplates use, so you can compare them directly. To find the real power in kW, multiply by the load’s power factor.

The default is 480 V three-phase, a common voltage for building services and datacenter feeders in North America. Change it for a 208 V or 415 V feed, or a single-phase supply.

A 480 V feeder’s two voltages. A service or feeder labeled 277/480 V or 480Y/277 V has 480 V between phases (line-to-line) and 277 V from each phase to neutral (480 ÷ √3, line-to-neutral). The amps on the breaker or feeder are per phase. Enter 480 V with three-phase selected; entering 277 V would understate the kVA by a factor of √3.

Worked example

A building has a 200 A, 480 V three-phase service available for a server room:

kVA = 1.732 × 480 × 200 ÷ 1,000 = 166.28 kVA (166,277 VA)

That is the full rating. The usable figure for a continuous load is lower; in North America, continuous loads are commonly planned at 80% of the breaker rating.

A 100 A, 208 V three-phase panel in an existing IT room:

kVA = 1.732 × 208 × 100 ÷ 1,000 = 36.03 kVA

Frequently Asked Questions

How many kVA is a 200 A, 480 V three-phase service?

1.732 × 480 × 200 ÷ 1,000 = 166.28 kVA. That is the apparent power at the full 200 A; how many kW it can deliver depends on the load's power factor.

How many kVA is a 100 A single-phase supply?

At 240 V, 100 × 240 ÷ 1,000 = 24 kVA; at 230 V it is 23 kVA. Single-phase kVA is simply volts × amps ÷ 1,000.

Can a UPS be matched to a feeder by comparing kVA alone?

Not reliably. Compare the UPS's maximum input current from its data sheet with the feeder. While it recharges its batteries and covers its own losses, a UPS can draw noticeably more input current than its output kVA suggests.

Why convert to kVA instead of kW?

Electrical equipment is limited by current, and kVA is current scaled by voltage, so it compares feeders, UPS systems, generators and transformers without knowing the load's power factor. Once you know the power factor, the kVA to kW calculator gives the real power.