Free tool
kVA to Amps Calculator
kVA times a thousand, divided by the voltage — and by 1.732 on three-phase. The arithmetic is one line. The two ways to put the wrong voltage into it are more common than the arithmetic is hard.
kVA × 1,000 ÷ volts, with no power factor
amps = kVA × 1,000 ÷ volts on single-phase, and amps = kVA × 1,000 ÷ (volts × √3) on three-phase using the line-to-line voltage. A 25 kVA transformer at 240 V delivers 104.2 A; a 75 kVA transformer at 208 V delivers 208.2 A per line.
No power factor is applied, because kVA is already apparent power. The errors that matter are in the voltage: a line-to-neutral figure (120 or 277) in the three-phase formula overstates the current by 1.73 times, and 120 V for a 120/240 V single-phase secondary doubles it. The tool flags both.
The rating
The nameplate kVA. Enter 500 VA as 0.5.
The voltage the kVA is rated at.
The answer
Full-load current
104.2 A
amps = kVA × 1,000 ÷ volts → 25 × 1,000 ÷ (240 V)
No power factor is applied, and none should be: kVA is already apparent power, the quantity current is drawn against.
What the number is
The current the equipment delivers at its full nameplate rating. It is a rating, not a measurement: a transformer or generator carrying less than its rated load delivers proportionally less.
What this does not tell you
The overcurrent protection. Transformer protection is set by NEC 450.3, whose primary and secondary percentages depend on the voltage class, the rated current and whether the secondary is protected as well. It is not a matter of rounding this figure up to a breaker size.
A conductor size. Ampacity depends on conductor material, insulation and terminal temperature ratings, raceway fill and ambient temperature, none of which are entered here.
Informational use only, please verify before you rely on it
This reproduces standard conversion arithmetic from apparent power in kVA to full-load current for single-phase and three-phase systems. It is a preparation aid, not a determination and not a design. It does not size overcurrent protection, which for transformers is governed by NEC 450.3, or conductors, which depend on material, insulation and terminal temperature ratings, raceway fill and ambient temperature. 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.
Where a kVA figure turns up on a project
On most residential and light-commercial jobs the kVA rating that matters is on equipment nobody on the job owns: the utility's service transformer. When the utility finds it cannot take a new load or a PV system's export, the finding is stated in kVA and the remedy is a larger one. Who pays for a utility transformer upgrade covers why the cost splits at the property line and how to find out before the customer signs; the interconnection layer is where that finding arrives.
The voltage input is where the mistakes live, and which voltage a building has depends on its service. Single-phase vs three-phase power explains 120/240 V split-phase against 208Y/120 and 480Y/277, and why a 240 V appliance on a 208 V building delivers less. For conversions in the other units, the amps to watts and watts to amps calculators handle real power with power factor applied.
Frequently Asked Questions
How do you convert kVA to amps?+
Multiply kVA by 1,000 to get volt-amperes, then divide by the voltage. On a single-phase system that is the whole calculation: a 25 kVA transformer at 240 V delivers 104.2 A. On a three-phase system you divide by the square root of three as well, about 1.732, using the line-to-line voltage: a 75 kVA transformer at 208 V delivers 208.2 A per line, and a 500 kVA transformer at 480 V delivers 601.4 A.
Why is there no power factor in a kVA to amps conversion?+
Because kVA is already apparent power — volts times amps — and current is drawn against apparent power, not against real power. Power factor is the ratio between kW and kVA. It belongs in a kW to amps conversion, where the watts figure leaves out part of the current, and it does not belong in a kVA one. Applying it to a kVA figure is a common error and it overstates the current by the same ratio it was meant to correct.
Which voltage do I use for a three-phase transformer?+
The line-to-line voltage: 208, 240 or 480. A wye secondary is written with two numbers, such as 208Y/120 or 480Y/277, and the second is the line-to-neutral voltage. Entering 120 or 277 into the three-phase formula divides by a voltage that is too small by a factor of 1.732 and overstates the current by the same amount. The tool flags both of those entries and shows the corrected figure.
What about a 120/240 V single-phase transformer?+
Use 240 V. A single-phase three-wire secondary — the ordinary residential service — is rated in kVA across the full 240 V winding, and each hot leg carries the resulting current. A 25 kVA transformer at 240 V delivers 104.2 A on each leg. Entering 120 V would double that to 208.3 A, which is not a current the transformer is rated to deliver on any conductor.
Is the full-load current the breaker size?+
No. It is the current the equipment is rated to deliver, which is the input to the protection calculation rather than its result. Transformer overcurrent protection is governed by NEC 450.3, which sets maximum primary and secondary percentages that depend on the voltage class, the rated current and whether the secondary is protected as well. The conductor sizing that follows depends on material, insulation and terminal ratings, raceway fill and ambient temperature. None of that is on this page.
Does this work for a generator rated in kVA?+
Yes — a generator's kVA rating converts to its rated current exactly as a transformer's does, using the voltage and phase of its output. That figure answers what the machine can deliver. It does not answer what size of machine a building needs, which depends on running and starting loads and is a separate calculation.
Is this a determination?+
No. It reproduces the standard conversion arithmetic as a preparation aid. It reports the full-load current at the nameplate rating and nothing else — not overcurrent protection, not conductor size, not whether an existing transformer has capacity for an added load, which on a utility-owned transformer is the utility's determination. Confirm against the equipment nameplate and with the authority having jurisdiction.
Related resources
Amps to Watts Calculator
Real power from current, with power factor — and what a breaker rating can carry.
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 →Single-Phase vs Three-Phase Power
Split-phase, 208Y/120 and 480Y/277, and what each one changes.
Learn more →Solar Interconnection Services
Where utility capacity findings arrive and get resolved.
Learn more →Utility findings, handled 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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