Calculate Volt Amps (VA) using Voltage and Current, or use VA to find Voltage or Current.
Volt Amps (VA)
Voltage (V)
Current (A)
Result:
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Understanding Volt Amps (VA)
Volt Amps (VA) is a unit of apparent power in an electrical system. It represents the product of the root-mean-square (RMS) voltage and the RMS current. Unlike Watts (W), which measure real power (the power actually doing useful work), Volt Amps measure apparent power, which includes both real power and reactive power (power that oscillates between the source and the load, not doing useful work but still consuming capacity).
The Basic Formula
The fundamental relationship between Voltage (V), Current (A), and Volt Amps (VA) is given by the formula:
VA = V × A
This formula holds true for the apparent power in a direct current (DC) circuit or a purely resistive alternating current (AC) circuit. In AC circuits with reactive components (like inductors and capacitors), the relationship becomes more complex and involves the power factor. However, the VA = V × A formula directly gives the apparent power (VA), which is crucial for sizing power sources, transformers, and circuit breakers.
Calculating Different Components
This calculator also allows you to determine Voltage or Current if you know the other two values.
To find Voltage (V): If you know the Volt Amps (VA) and the Current (A), you can rearrange the formula:
V = VA / A
To find Current (A): If you know the Volt Amps (VA) and the Voltage (V), you can rearrange the formula:
A = VA / V
Why is VA Important?
Volt Amps are critical in electrical engineering and power systems for several reasons:
Sizing Transformers: Transformers are rated in VA. Their capacity to handle apparent power directly relates to their VA rating.
Power Supplies: The total power capacity of a power supply unit (PSU) is often specified in VA.
Generators and UPS Systems: Uninterruptible Power Supplies (UPS) and generators are rated in VA to indicate their maximum apparent power output.
Circuit Protection: Fuses and circuit breakers are selected based on the current they can safely handle, but the total VA load determines the necessary current at a given voltage.
Cable Sizing: While not the sole factor, VA is considered when determining the appropriate gauge for electrical wiring.
Apparent Power vs. Real Power (Watts)
In AC circuits, the relationship between apparent power (VA) and real power (W) is defined by the power factor (PF):
Watts (W) = VA × Power Factor (PF)
The power factor is a value between 0 and 1 that indicates how effectively electrical power is being converted into useful work. A purely resistive load has a power factor of 1 (VA = W). Loads with inductive or capacitive components have power factors less than 1, meaning VA will be greater than W.
Example Calculations
Let's walk through some examples using our calculator:
Calculating VA: If a device draws 10 Amps (A) at 120 Volts (V):
VA = 120 V × 10 A = 1200 VA
Enter 120 in the Voltage field and 10 in the Current field, and select "Volt Amps (VA)". The result will be 1200 VA.
Calculating Voltage: If a UPS system has a capacity of 2000 VA and is supplying 8 Amps (A) to a load:
V = 2000 VA / 8 A = 250 V
Enter 2000 in the VA field and 8 in the Current field, and select "Voltage (V)". The result will be 250 V.
Calculating Current: If a transformer is rated for 500 VA and operates at 240 Volts (V):
A = 500 VA / 240 V ≈ 2.08 A
Enter 500 in the VA field and 240 in the Voltage field, and select "Current (A)". The result will be approximately 2.08 A.
This calculator simplifies these common electrical calculations, providing quick and accurate results for various applications.
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var voltage, current, va;
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resultValueElement.innerText = "Error";
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va = voltage * current;
resultValueElement.innerText = va.toFixed(2);
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current = parseFloat(document.getElementById("currentForVoltage").value);
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resultValueElement.innerText = "Error";
resultUnitElement.innerText = "Please enter valid positive numbers for VA and Current.";
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if (isNaN(va) || isNaN(voltage) || va <= 0 || voltage <= 0) {
resultValueElement.innerText = "Error";
resultUnitElement.innerText = "Please enter valid positive numbers for VA and Voltage.";
return;
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current = va / voltage;
resultValueElement.innerText = current.toFixed(2);
resultUnitElement.innerText = "A";
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}
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