Free tool
Amps to kVA Calculator
Amps times volts, divided by a thousand — and times 1.732 on three-phase. The arithmetic is one line. What trips people up is the voltage, and treating a breaker rating as if it were a load.
Amps × volts ÷ 1,000, with no power factor
kVA = amps × volts ÷ 1,000 on single-phase, and kVA = amps × volts × √3 ÷ 1,000 on three-phase using the line-to-line voltage. 100 A at 240 V is 24 kVA; 208 A at 208 V three-phase is about 75 kVA.
No power factor is applied — amps times volts already is apparent power. A 200 A service at 240 V is rated for 48 kVA, which is its capacity, not what the house draws. The tool keeps those apart and flags a line-to-neutral voltage entered as three-phase.
The current
At the stated voltage.
120 or 240 on a house.
The answer
Apparent power
24.00 kVA
kVA = amps × volts ÷ 1,000 → 100 A × 240 V ÷ 1,000
No power factor is applied: amps times volts already is apparent power. For real power in kW, the power factor comes in — that is a different conversion.
Where it sits among common single-phase ratings
The nearest common nameplate at or above 24.00 kVA is 25 kVA (the one below is 15 kVA). A reference point, not a selection: choosing a transformer depends on the demand calculation, continuous and motor loads, growth, and — on a utility-owned unit — the utility.
What this does not tell you
A transformer or generator size. Selection starts from a demand load calculation and the equipment's duty, not from one current reading. Transformer overcurrent protection is set by NEC 450.3.
Real power. kVA includes the reactive part of the current. For kW, multiply by the power factor.
Informational use only, please verify before you rely on it
This reproduces standard conversion arithmetic from current to apparent power in kVA for single-phase and three-phase systems. It is a preparation aid, not a determination and not a design. It does not select or size a transformer or generator, which starts from a demand load calculation, and it does not size conductors or overcurrent protection; transformer protection is governed by NEC 450.3. Whether a utility-owned transformer has capacity for added load or export is the utility's determination. Confirm against the equipment nameplate and with the authority having jurisdiction.
This tool is provided for general informational and educational purposes only. Its output is an illustrative estimate generated from the values you enter and from general assumptions that will not match every deal, market, lender, or homeowner. It is not tax, legal, accounting, financial, or professional advice, and it is not a quote, an offer, a credit decision, or a guarantee of pricing, approval, timing, savings, or eligibility.
You are solely responsible for independently confirming all information presented here including any figures, rates, fees, margins, timelines, tax treatment, and federal, state, local, or utility incentives, with the applicable lender, authority having jurisdiction, and your own qualified tax, legal, and financial advisors before acting on it, relying on it, or presenting it to a homeowner or any third party. Incentive programs, lender terms, and permitting requirements change frequently and vary by jurisdiction.
Seamless Home is not a tax advisor, law firm, lender, or licensed installing contractor, and makes no representation or warranty as to the accuracy, completeness, or currency of the information produced by this tool. To the fullest extent permitted by law, Seamless Home accepts no liability for any decision made or action taken in reliance on it.
When the current is known and the kVA is the question
The usual reason to go from amps to kVA on a project is a capacity conversation with the utility: a service upgrade, an EV charger or heat pump added to a house, a PV system's export. The utility frames its answer in kVA of transformer capacity. Who pays for a utility transformer upgrade covers why that cost splits at the property line and how to find out early.
Going the other way — current from a kVA nameplate — is the kVA to amps calculator, which uses the same standard sizes, and the VA to amps calculator covers small equipment rated in VA. For real power rather than apparent, the amps to kW calculator applies the power factor, and what power factor is explains why the two answers differ.
Frequently Asked Questions
How do you convert amps to kVA?+
Multiply amps by volts and divide by 1,000. On single-phase that is the whole calculation: 100 A at 240 V is 24 kVA. On three-phase, multiply by the square root of three as well, about 1.732, using the line-to-line voltage and the current in one line: 208 A at 208 V three-phase is about 75 kVA, and 100 A at 480 V three-phase is about 83.1 kVA.
Why is there no power factor in an amps to kVA conversion?+
Because volts times amps is apparent power by definition, and kVA is apparent power. Power factor is the ratio between real power in kW and apparent power in kVA, so it belongs in an amps to kW conversion. Applying it here gives a kW figure with a kVA label on it.
How many kVA is a 200 amp service?+
A 200 A, 120/240 V single-phase service is rated for 200 × 240 ÷ 1,000 = 48 kVA. That is the capacity of the service equipment, not the house's demand: an ordinary home draws a fraction of it most of the time, and the utility sizes its transformer from the load it expects, not from the main breaker.
Which voltage do I use for three-phase?+
The line-to-line voltage: 208, 240 or 480. On a wye system written 208Y/120 or 480Y/277, the second number is the line-to-neutral voltage. Entering it understates the kVA by a factor of about 1.73. The calculator flags 120 V and 277 V on three-phase and shows the corrected figure.
Does this tell me what size transformer I need?+
No. It shows where the figure sits among common nameplate ratings as a reference point. Selecting a transformer starts from a demand load calculation — continuous loads, motor starting, diversity and growth — and its protection is governed by NEC 450.3. On a utility-owned transformer, the size is the utility's decision.
What is the difference between amps to kVA and amps to kW?+
kVA is the apparent power the current represents; kW is the part of it doing real work. kW = kVA × power factor. For a heater the two are equal; for motors and electronics kW is smaller. Equipment ratings for transformers, generators and UPS units are given in kVA because the current, and the heat it makes in the windings, follows kVA.
Is this a determination?+
No. It reproduces the standard conversion arithmetic as a preparation aid. It does not size a transformer, generator, conductor or overcurrent device, and it does not decide whether an existing transformer has capacity for an added load. Confirm against equipment nameplates and with the authority having jurisdiction.
Related resources
kVA to Amps Calculator
Full-load current from a kVA rating — the reverse direction.
Learn more →Amps to kW Calculator
Real power from current, with power factor applied.
Learn more →kVA to kW Calculator
Real power from a kVA rating — conversion, not generator sizing.
Learn more →Who Pays for a Utility Transformer Upgrade?
Why the cost splits at the property line, and how to find out early.
Learn more →Utility capacity findings, caught before they stall the job
Seamless Home runs the design, permit and interconnection layer for the partners it works with, which is where a transformer capacity finding gets caught early rather than after install. Coverage is confirmed per service area rather than promised as blanket availability.
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