kW to Amps Calculator

Convert a rack or room load in kilowatts to the current it draws per phase, and the circuit rating that keeps it at 80%.

Inputs

Result

Enter the load in kW to see the current.

Related tools

How the calculation works

The current a load draws depends on its real power, the voltage, the circuit type and the power factor (PF):

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

The default is 208 V three-phase at a power factor of 1.0, because racks drawing more than a few kilowatts are often fed with three-phase circuits in North American colocation. Change the voltage and phase to match the circuit you are quoting. For IT equipment, 0.9 or 0.95 are common planning values for PF; a lower PF means more current for the same kW.

The calculator also shows the apparent power in kVA (kW ÷ PF) and the smallest circuit rating that keeps the load at or below 80% of the breaker (amps ÷ 0.8). That 80% figure reflects the North American practice for continuous loads; it is planning context, not electrical advice, and other countries’ rules differ.

Line-to-line on a three-pole breaker. A three-phase rack circuit from a 208Y/120 V panel uses a three-pole breaker with three hot conductors. The voltage between any two of them is 208 V (line-to-line); between any one and neutral it is 120 V (208 ÷ √3, line-to-neutral). Enter 208 V. The answer is the current in each of the three conductors, which is the number to compare with the breaker’s rating.

Worked example

A colocation cabinet is planned for 10 kW of servers with a power factor of 0.95, on a 208 V three-phase circuit:

amps per phase = 10,000 ÷ (1.732 × 208 × 0.95) = 10,000 ÷ 342.3 = 29.22 A
apparent power = 10 ÷ 0.95 = 10.53 kVA
at 80% loading, the circuit needs a rating of at least 29.22 ÷ 0.8 = 36.52 A, so a 30 A three-phase circuit is too small and a 40 A one fits

The same cabinet in a facility that distributes 415 V three-phase (415Y/240 V):

amps per phase = 10,000 ÷ (1.732 × 415 × 0.95) = 14.64 A
applying the same 80% planning margin gives at least 18.31 A, so a 16 A three-phase circuit is too small and a 32 A one fits

Frequently Asked Questions

How many amps is 10 kW at 208 V three-phase?

At a power factor of 1.0, 10,000 ÷ (1.732 × 208) = 27.76 A per phase. At a power factor of 0.95 it is 29.22 A per phase. On a single-phase 208 V circuit, the same 10 kW at a power factor of 1.0 would draw 48.08 A.

Is a 30 A three-phase circuit rated for 30 A in total?

No. A three-phase breaker's rating applies to each of its three poles, and the calculator's current is per phase, so compare the two directly. A 10 kW rack at 208 V and a power factor of 0.95 draws 29.22 A per phase; keeping that at 80% needs a rating of at least 36.52 A, so a 40 A three-phase circuit rather than a 30 A one.

Should I use the kW figure from the server spec sheet?

A spec sheet usually gives the power supply rating, which is a maximum. Sizing from it gives a safe but often oversized circuit. A measured peak from similar servers, or the vendor's power calculator for your exact configuration, is closer to what the rack will draw; then leave headroom for growth.

How do A and B feeds change the amps I plan for?

A dual-corded rack normally shares its load across both feeds, so each carries about half. If one feed fails, the other carries all of it, so size each feed for the full kW, not half. For 10 kW at 208 V three-phase and a power factor of 0.95, that means 29.22 A per phase on each feed.