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kW to kVA Calculator

Convert real power in kW into apparent power in kVA for generator and transformer sizing.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Apparent power at PF 0.8

100 kVA

High confidence

kVA = kW ÷ power factor, taken here as 0.8. Motor inrush frequently determines generator size rather than running load — check starting current separately.

Conversion factor applied
1.25 kVA per kW

Sizing a generator, transformer or supply from a known load means working from real power back to apparent power, because it is apparent power that the conductors and switchgear actually have to carry. Dividing by the power factor does that, and the worse the power factor the larger the required capacity for identical useful output — current flows and heats cables whether or not it is doing work. Two checks belong alongside the arithmetic. A generator should be assessed against both its kW and its kVA rating, taking whichever binds first. And motor starting current, which can be several times the running figure, frequently sets the machine size regardless of what the steady-state calculation says.

Add the equipment this sizes

This result is a specification — 100 kVA — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Apparent power = real power / power factor; kVA = kW / PF

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Frequently asked questions

Why does a worse power factor need a bigger supply?
Because the supply has to carry the current, and a poor power factor means more current for the same useful work. The conductors, switchgear and transformer all size on apparent power, so a low power factor consumes capacity without doing anything with it.
Should I size a generator on this figure?
On this figure and the kW figure both, then take the more demanding. Check starting loads separately — motor inrush can far exceed running apparent power and is often what actually determines the set size.
Do electronics have a poor power factor?
Older switch-mode supplies often did. Modern equipment above a modest power threshold generally has correction built in, so a contemporary IT or LED load is usually better behaved than its reputation suggests. Measure rather than assume on a large installation.