Electrical calculation tool
Voltage Calculator
Solve voltage, current, resistance, and power for a simple circuit. The calculator uses Ohm's law for resistive loads and shows the formula table so the result is easy to verify.
Voltage Inputs
Choose the unknown value, then enter the other circuit values. For AC circuits, reactive loads, or building wiring, treat this as a basic estimate only.
Presets
Direct Answer
With the current inputs, the circuit estimate is:
Power
24.00 W
Voltage 12.00 V x current 2.00 A
| Result | Value | Formula |
|---|---|---|
| Voltage | 12.00 V | I x R |
| Current | 2.00 A | V / R |
| Resistance | 6.00 ohms | V / I |
| Energy | 0.096 kWh | (W x hours) / 1000 |
| Estimated cost | $0.02 | kWh x rate |
Formula and Method
| Unknown | Formula | Use when |
|---|---|---|
| Voltage | V = I x R | Current and resistance are known. |
| Current | I = V / R | Voltage and resistance are known. |
| Resistance | R = V / I | Voltage and current are known. |
| Power | P = V x I | Voltage and current are known. |
Before You Work on a Circuit
- De-energize the circuit before touching conductors or terminals.
- Verify ratings on the power supply, breaker, wire, connector, fuse, and load.
- Do not use this page to size household wiring, breakers, or code-regulated installations.
- Use a qualified electrician for live work, building wiring, service panels, or unfamiliar circuits.
Worked Example
Suppose a 12 V DC LED strip draws 2 A. Power is 12 x 2 = 24 W. If it runs for 4 hours, energy use is 24 x 4 / 1000 = 0.096 kWh. At $0.16 per kWh, that short run costs about $0.02.
Official References
These references are used for unit definitions and safety context. They do not replace local electrical code, product manuals, or a qualified professional.
Voltage Calculator FAQ
What formula does the voltage calculator use?
For simple direct-current resistive circuits, it uses Ohm's law: voltage equals current multiplied by resistance, or V = I x R. It also calculates current as I = V / R, resistance as R = V / I, and power as P = V x I.
Can this calculator be used for AC household wiring?
Use it only for basic estimates. Household AC systems can involve impedance, phase, breaker ratings, code requirements, and safety hazards that this simple calculator does not model.
Why does power change when voltage or current changes?
Electrical power in watts is the product of voltage and current. If a device draws 2 amps at 12 volts, the estimated power is 24 watts.
Is 50 volts always safe?
No. OSHA materials treat exposed parts at 50 volts or more as a serious hazard, and lower voltages can still be dangerous in some conditions. De-energize circuits before working on them.
About This Calculator
Free voltage calculator for Ohm's law. Solve voltage, current, resistance, power, and energy use with formulas, unit definitions, examples, and electrical safety references.
Frequently Asked Questions
What is Ohm's Law?
Ohm's law describes the relationship between voltage, current, and resistance in a simple resistive circuit. The core formula is V = I x R.
What formula does the Voltage Calculator use?
The calculator uses V = I x R for voltage, I = V / R for current, R = V / I for resistance, and P = V x I for power. It also estimates kWh from watts and runtime.
Can I use this for household AC wiring?
Use it only for basic estimates. Household AC wiring can involve impedance, phase, breaker ratings, code requirements, and safety hazards that a simple Ohm's law calculator does not model.
Why does power change when voltage or current changes?
Power in watts equals voltage multiplied by current. A 12 volt load drawing 2 amps is about 24 watts before accounting for real-world losses or device-specific behavior.
Is this calculator a substitute for an electrician?
No. Use it for educational estimates and simple checks only. De-energize circuits before working on them and use a qualified electrician for live work, service panels, building wiring, or code-regulated installations.
The SuperCalc Editorial Team maintains calculator interfaces, formula notes, examples, and supporting explanations. Methods, assumptions, source links, and review depth vary by calculator and are documented on the relevant page where available.