kW to VA Calculator
Convert kilowatts to volt-amperes using power factor. Calculate apparent power (VA) needed for UPS sizing, wiring, and transformer selection from real power load.
Volt-Amperes
2500 VA
Power (kW)
2
Apparent Power (kVA)
2.5
Apparent Power (VA)
2500
Formula Used
VA = (kW × 1000) / PF = (2 × 1000) / 0.8
VA = (kW × 1000) / PF
About the kW to VA Calculator
A kW to VA calculator converts real power in kilowatts to apparent power in volt-amperes using power factor — essential for UPS sizing, wiring design, and selecting circuit protection for loads with known wattage but variable power factor. When specifying UPS systems, power distribution units (PDUs), or circuit breakers for AC loads, you must work in VA (or kVA), not watts. A 2 kW server load with PF 0.9 requires 2,222 VA from the UPS; the same load at PF 0.6 requires 3,333 VA — more than 50% more UPS capacity for the same real power delivered. Getting this wrong means selecting an undersized UPS that overloads when the server draws full current. Our kW to VA calculator works for any combination of kW and power factor from 0.1 to 1.0, and also shows the reactive power (VAR) component for a complete picture of the power triangle. It is used by data center engineers, IT managers, commercial electricians, and industrial facility managers worldwide.
Formula
VA = (kW × 1000) / PF | VAR = VA × √(1 - PF²) | kVA² = kW² + kVAR²
How It Works
VA = (kW × 1000) / PF. kVA = kW / PF. Reactive power: VAR = VA × sin(arccos(PF)) = VA × √(1 - PF²). Example 1 (IT equipment): 3 kW server at PF 0.95: VA = 3,000 / 0.95 = 3,158 VA (3.16 kVA). A 3,500 VA UPS would handle this with adequate headroom. Reactive: VAR = 3,158 × √(1 - 0.95²) = 3,158 × 0.312 = 985 VAR. Example 2 (motor load): 5.5 kW motor at PF 0.75: VA = 5,500 / 0.75 = 7,333 VA (7.33 kVA). A 7.5 kVA transformer or generator is the minimum; 10 kVA recommended for startup surge. Example 3 (mixed office): 10 kW total at PF 0.85: VA = 10,000 / 0.85 = 11,765 VA (11.76 kVA) → 15 kVA UPS recommended with 25% headroom.
Tips & Best Practices
- ✓UPS sizing with headroom: size UPS to 125% of calculated VA demand. If your servers total 8 kW at PF 0.92 = 8,696 VA, select a UPS rated for at least 10,870 VA. Standard next size up: 12 kVA or 15 kVA UPS.
- ✓Mixed PF environments: data centers often mix servers (PF 0.9–1.0) with CRAC units (PF 0.85–0.90) and lighting (PF 0.5–0.9 without PFC). Calculate VA separately for each load type, then sum, rather than applying an average PF to total kW.
- ✓PDU (Power Distribution Unit) rating: PDUs are rated in kVA/kW pairs (e.g., 8.64 kW / 10 kVA). The kVA limit is binding: a PDU rated 10 kVA can handle 8.64 kW at PF 0.864 — load it with high-PF servers up to 9.9 kW, or lower-PF equipment to only 6 kW at PF 0.6.
Who Uses This Calculator
Data center engineers converting server power draws (kW) to VA for UPS and PDU sizing. Commercial electricians sizing wiring and circuit breakers for motor and lighting loads where wattage is specified. IT managers verifying that existing UPS capacity can handle server expansion plans. Facilities engineers performing load studies for power infrastructure upgrades.
Optimised for: USA · UK · Canada · Australia · Calculations run in your browser · No data stored
Frequently Asked Questions
How do I convert kW to VA?
VA = (kW × 1000) / PF. Example: 3 kW load with PF 0.75: VA = 3,000 / 0.75 = 4,000 VA (4 kVA). Lower power factor means higher VA for the same real power.
Why must VA be higher than watts for most loads?
Most AC loads (motors, fluorescent ballasts, switching power supplies) draw reactive current in addition to real current. This reactive component does no useful work but must still flow through wires and breakers, increasing the VA requirement.
How do I size a UPS using kW?
Convert your total load from kW to VA using the expected PF. Most IT equipment has PF 0.9–1.0. A 2 kW server load at PF 0.9: VA = 2,000 / 0.9 = 2,222 VA. Size the UPS to 125% capacity: 2,222 × 1.25 = 2,778 VA → 3,000 VA UPS.