Calculate Volt Amps
Enter the electrical values, choose the system type, and calculate apparent power in VA and kVA.
Example Data Table
| System | Current | Voltage | Calculation | Apparent power |
|---|---|---|---|---|
| Single-phase AC | 10 A | 230 V | 230 × 10 | 2,300 VA |
| DC circuit | 5 A | 120 V | 120 × 5 | 600 VA |
| Three-phase line-to-line | 20 A | 400 V | 1.732 × 400 × 20 | 13,856 VA |
| Three-phase line-to-neutral | 8 A | 230 V | 3 × 230 × 8 | 5,520 VA |
| Single-phase AC | 16 A | 230 V | 230 × 16 | 3,680 VA |
Formula Used
DC and single-phase AC
Apparent power equals voltage multiplied by current.
VA = V × AThree-phase AC with line-to-line voltage
Use the square root of three when the stated voltage is measured between phases.
VA = √3 × V(line-to-line) × AThree-phase AC with line-to-neutral voltage
Use three when the stated voltage is measured from one phase to neutral.
VA = 3 × V(line-to-neutral) × AEstimated watts
Power factor estimates real power from apparent power. It does not replace a measured power study.
W = VA × power factorHow to Use This Calculator
- Enter the circuit current and choose mA, A, or kA.
- Enter the circuit voltage and choose V or kV.
- Select DC, single-phase, or the matching three-phase voltage reference.
- Enter the load power factor for an estimated watt value.
- Select Calculate Volt Amps and review VA, kVA, W, and kW.
- Download the result as CSV or PDF when needed.
Understanding Volt Amps
Volt amps measure apparent electrical power. They combine voltage and current. The result shows the total electrical capacity supplied to a load. This value is useful when sizing transformers, generators, inverters, breakers, and uninterruptible power supplies. It describes the electrical demand seen by the source.
A volt amp is not always equal to a watt. Watts show real power. Real power performs useful work. Motors, chargers, and electronic devices can draw current that does not convert fully into useful work. Their power factor explains the difference. A power factor of one makes watts and volt amps equal. A lower factor makes wattage smaller than apparent power.
Single Phase and DC Loads
For direct current and single phase alternating current, apparent power is voltage multiplied by current. A 230 volt device drawing 10 amps uses 2,300 volt amps. The same amount is 2.3 kilovolt amps. This simple method works for many household circuits and smaller commercial loads.
Voltage must represent the actual circuit value. Current should represent the expected running current. Use rated values when planning equipment capacity. Use measured values when checking an existing circuit. Startup current can be much higher than running current. Motors and compressors often need extra capacity during starting. Do not size protective equipment from apparent power alone. Follow electrical rules and equipment instructions.
Three Phase Calculations
Balanced three phase systems need a different multiplier. When voltage is measured line to line, multiply voltage, current, and the square root of three. This factor is about 1.732. A three phase load at 400 volts and 20 amps therefore needs about 13,856 volt amps. That equals about 13.86 kilovolt amps.
Some systems use line to neutral voltage. In that case, multiply voltage by current and three. Choose the voltage reference carefully. Mixing line to line and line to neutral values causes incorrect results. Check the panel label, wiring diagram, or meter setting before calculation. For unbalanced loads, calculate each phase separately. Add the phase results for a practical total.
Planning Capacity Safely
The calculator also estimates watts when you enter a power factor. This estimate helps compare apparent power with utility energy use. However, volt amps remain important for source equipment. A generator or transformer must carry the full apparent load. A low power factor may increase current without increasing useful wattage by the same amount.
Leave room for future loads. Consider continuous operation, temperature, conductor ratings, and local electrical requirements. Avoid running equipment at its maximum rating for long periods. Complex systems need review by a qualified electrician or engineer. Use this calculator as a planning aid. Confirm final designs with applicable codes and manufacturer data.
Record the inputs and result for future reference. Recheck unit selections before ordering electrical equipment. Clear labels prevent costly mistakes during installation, testing, maintenance, and future expansion at every site on demanding projects.
Frequently Asked Questions
What is a volt amp?
A volt amp, written VA, is apparent power. It combines the circuit voltage and current. It is important for equipment that supplies electrical capacity, such as transformers, inverters, and generators.
Are volt amps and watts the same?
They are equal only when power factor is 1.00. A lower power factor means watts are lower than VA. Motors and many electronic loads often have a power factor below one.
How do I calculate VA for single-phase power?
Multiply voltage by current. For example, 230 volts multiplied by 10 amps equals 2,300 VA. Use the rated or measured circuit values that match the equipment condition.
How do I calculate VA for three-phase power?
For line-to-line voltage, use square root of three multiplied by voltage and current. For line-to-neutral voltage, use three multiplied by voltage and current. Select the correct voltage reference first.
What does kVA mean?
kVA means kilovolt amps. One kVA equals 1,000 VA. Larger electrical equipment ratings are often expressed in kVA because the numbers are easier to read.
Can I enter milliamps or kiloamps?
Yes. Choose mA for milliamps, A for amps, or kA for kiloamps. The calculator converts the selected unit to amps before applying the electrical formula.
Which voltage should I use?
Use the voltage that matches your selected system. For three-phase circuits, confirm whether the voltage is line-to-line or line-to-neutral. Panel labels and equipment documents usually show this information.
Why does the calculator ask for power factor?
Power factor allows an estimated watt calculation. VA represents apparent power, while watts represent real power. The VA result remains valid without changing its formula.
Does this tool handle unbalanced three-phase loads?
It gives a balanced-load estimate. For unbalanced circuits, calculate each phase using its own voltage and current. Add the phase results after checking the circuit arrangement.
Can I use this result to size a breaker?
No single calculation can safely size protection. Breaker selection also needs conductor ratings, continuous-load rules, starting current, local codes, and manufacturer requirements. Consult a qualified professional for final design work.
Can I download the calculation?
Yes. After calculating, use Download CSV for a spreadsheet-friendly file. Use Download PDF for a compact summary that includes the inputs, formula, and calculated results.
Enter correct values and choose the proper electrical system.