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TRANSFORMER PLANNING RESOURCE

TRANSFORMER KVA CALCULATOR

Convert your electrical load into kilovolt-amperes (kVA), calculate transformer full-load current, and compare ratings for your project. Use your results to prepare specifications for an equipment discussion, with final selection confirmed by a qualified engineer.

A planning basis. Not a final specification.

Sunbelt Solomon

Transformer calculator

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What would you like to calculate?

Phase
Load information

Do you expect the load to grow? optional

Ratings to compare pick up to 3

We pre-select the ratings around your load. Tap to change them.

Planning a project around this unit?Get a list of the equipment, testing and engineering work it will likely need.

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We'll send these results to your inbox. A copy goes to the Sunbelt Solomon team so we can help with next steps.

    Results are estimates for planning purposes. Final transformer selection should account for load type, motor starting, harmonics, ambient conditions and applicable codes. Confirm with a qualified engineer. Contact us for more information: 888-691-4712.

    How to use the calculator
    Sizing Formulas
    Project Fit
    Definitions
    FAQs

    HOW TO USE THE TRANSFORMER CALCULATOR

    Start with the information available for your project: equipment load, supply voltage, phase, or an existing transformer nameplate. Select the calculator mode that matches your question. Enter voltage in volts, so a 13.8 kilovolt supply is entered as 13,800 volts. The results provide a planning basis for comparing equipment requirements.

    Find a transformer Size

    Enter your load in kVA, kilowatts (kW), or amps, and choose single-phase or three-phase. When entering kW, use the applicable power factor. When entering amps, include voltage. Add a growth allowance if your project calls for additional capacity.

    Calculate transformer amps

    Enter the transformer rating in kVA or megavolt-amperes (MVA), along with primary and secondary voltages. Review the calculated full-load current on each side. For three-phase equipment, provide delta or wye connections when you need the winding turns ratio.

    Compare transformer ratings

    Professional service delivery using advanced equipment and proven methodologies.Compare up to three ratings against your entered load and growth allowance. Review calculated loading, spare capacity, and full-load current where voltage is supplied. Treat the fit labels as load comparisons, not confirmation that a transformer meets every project requirement.

    Transformer sizing and conversion formulas

    These formulas express the relationship between apparent power, voltage, and current. For balanced three-phase calculations, use line-to-line voltage and line current. Keep units consistent: the formulas below use volts, amps, and kVA. They do not calculate motor-starting performance, fault current, or protective-device settings.

    Calculation

    Single-phase apparent power

    Three-phase apparent power

    Single-phase full-load current

    Three-phase full-load current

    Convert kW to kVA

    Convert MVA to kVA

    Add a selected growth allowance

    Calculation

    kVA = volts × amps ÷ 1,000

    kVA = √3 × line-to-line volts × line amps ÷ 1,000

    Amps = kVA × 1,000 ÷ volts

    Amps = kVA × 1,000 ÷ (√3 × line-to-line volts)

    kVA = kW ÷ power factor

    kVA = MVA × 1,000

    Planning load = load kVA × (1 + growth percentage ÷ 100)

    Use the actual power factor when available. The calculator’s default is an assumption, not a measurement of your equipment. Changing power factor changes the kVA calculated from a kW load.

    Check the transformer fit for your project

    A kVA result answers a capacity question. Your transformer also needs the correct primary and secondary voltages, phase, connections, and configuration for the installation. For a replacement, compare the existing nameplate and drawings with the proposed equipment specifications. For an expansion, have the planned load and operating conditions reviewed before selecting a rating.

    Electrical requirements

    Document primary and secondary voltages, phase, frequency, connection requirements, and available nameplate information. Identify motor loads or nonlinear loads that require additional evaluation. Full-load current is not a fault-current calculation or a breaker-setting recommendation.

    Site and installation fit

    Include the required transformer configuration, dimensions, access constraints, and termination arrangement. A matching kVA rating does not establish physical compatibility. Share site drawings or a one-line diagram so the appropriate team can evaluate the equipment interface.

    Capacity and project timing

    Separate your present load from planned additions and document the growth allowance you use. Include your project location and required date when requesting options. Our team can review the equipment requirement and verify availability for the specific scope.
    Send your transformer specifications

    Understand your transformer calculation

    Equipment schedules and nameplates can describe the same project using different units. Understanding those units helps you supply consistent inputs and interpret the results. Apparent power, real power, and current answer different questions. Use the definitions below when preparing information for your electrical team.

    What is kVA?

    Kilovolt-amperes measure apparent power in an alternating-current system. Transformer capacity is expressed in kVA or MVA. Your calculated load kVA is a starting point for capacity planning, not a complete equipment specification.

    What is the difference between kW and kVA?

    Kilowatts measure real power. Kilovolt-amperes measure apparent power, and power factor relates the two: kW = kVA × power factor. When you know kW but need kVA, divide by the applicable power factor rather than treating the values as interchangeable.

    What are volts and amps?

    Volts measure electrical potential difference, and amps measure electrical current. For a given kVA rating and phase, calculated current changes with voltage. Keep primary and secondary voltage values distinct when reviewing transformer full-load current.

    What is power factor?

    Power factor is the ratio of real power to apparent power. Enter it as a decimal, such as 0.9, rather than a percentage such as 90. Use equipment information or a qualified electrical review to establish the value for your application.

    Transformer calculator frequently asked questions

    For an amps-to-kVA calculation, enter voltage, current, and phase. For a kW-to-kVA conversion, provide the load and applicable power factor. If you already know the load in kVA, enter that value directly. Confirm the source and units of each input before comparing transformer ratings.
    For single-phase equipment, multiply kVA by 1,000 and divide by voltage. For balanced three-phase equipment, divide by the line-to-line voltage multiplied by the square root of three. Use the transformer-amps mode to calculate primary and secondary full-load current from the entered rating and voltages.
    The appropriate allowance depends on your planned additions and operating requirements. The calculator lets you enter a growth percentage so you can compare its effect on planning capacity. A qualified engineer should assess motor starting, harmonics, loading patterns, and site conditions rather than apply one blanket allowance to every project.
    No. The comparison describes calculated loading against the selected kVA rating using your inputs and growth allowance. It does not verify voltage compatibility, physical fit, protection, or application-specific performance. Have a qualified engineer review the equipment specifications and installation requirements before making your final selection.
    The main calculations cover apparent power, full-load current, rating comparisons, and voltage or winding ratios where inputs allow. They do not establish final protective-device settings or conductor sizes. Any additional equipment suggestions are planning prompts that require review using the applicable system data and project requirements.
    Send your calculated load or required rating, primary and secondary voltages, phase, frequency, project location, and required date. Include a nameplate photo, equipment specification, or one-line diagram if available. Explain whether you are replacing equipment, expanding capacity, or planning temporary power so our team can review the requirement.

    Review your transformer requirements with our team

    Share your calculator results and project specifications with Sunbelt Solomon. We can discuss the equipment requirements and next steps, with technical suitability, availability, and project scope confirmed through review.

    Request a transformer quote
    Calculator results are planning estimates. Final transformer selection requires review of load characteristics, motor starting, harmonics, ambient conditions, installation requirements, and applicable codes by qualified professionals.