The Watts, Volts, Amps, and Ohms Calculator makes it easy to calculate electrical power, voltage, current, and resistance in seconds. Enter any two known values, choose what you want to calculate, and get your result with the formula used. It’s a handy tool for students, electricians, electronics enthusiasts, and anyone working with electrical circuits.
Watts / Volts / Amps / Ohms Calculator
Find power, voltage, current or resistance from any two compatible known values. Results update automatically as you type.
Calculation Results
View your answer, calculation formula and electrical reference formulas.
6 Ω
Default example: 12 V and 2 A give 6 Ω.
Formula Used
R = V / I
Resistance equals voltage divided by current.
Electrical Formulas
How to Use the Watts, Volts, Amps, and Ohms Calculator
Using this calculator is simple, even if you’re not familiar with electrical formulas.
- Choose what to calculate: Select Watts, Volts, Amps, or Ohms from the dropdown menu.
- Enter two known values: Fill in the two electrical values you already know, leaving the target quantity and unused field blank.
- Click Calculate: The calculator will display the answer along with the formula used.
- Copy your result: Use the Copy Result button to save the calculation for later.
- Start again: Click Clear All to remove your entries or Reload Defaults to restore the example values.
Electrical Formulas Used in the Calculator
The calculator uses Ohm’s law and standard electrical power formulas to find the missing value.
| Quantity | Formula | What It Calculates |
|---|---|---|
| Resistance | R = V / I | Ohms from volts and amps |
| Resistance | R = V² / P | Ohms from volts and watts |
| Resistance | R = P / I² | Ohms from watts and amps |
| Current | I = V / R | Amps from volts and ohms |
| Current | I = P / V | Amps from watts and volts |
| Current | I = √(P / R) | Amps from watts and ohms |
| Voltage | V = I × R | Volts from amps and ohms |
| Voltage | V = P / I | Volts from watts and amps |
| Voltage | V = √(P × R) | Volts from watts and ohms |
| Power | P = V × I | Watts from volts and amps |
| Power | P = V² / R | Watts from volts and ohms |
| Power | P = I² × R | Watts from amps and ohms |
Here, V stands for voltage, I for current, R for resistance, and P for power.
Frequently Asked Questions
1. How do I calculate watts from volts and amps?
Multiply the voltage by the current. The formula is P = V × I. For example, a 12-volt circuit drawing 2 amps uses 24 watts of power.
2. How do I calculate amps from watts and volts?
Divide the power in watts by the voltage in volts. The formula is I = P / V. For example, a 100-watt device operating at 20 volts draws 5 amps.
3. How do I calculate ohms from volts and amps?
Divide the voltage by the current using R = V / I. For example, 12 volts divided by 2 amps gives a resistance of 6 ohms.
4. Can I calculate volts, watts, amps, or ohms if I know only one value?
Generally, no. You need two suitable known electrical values to calculate the third quantity using the formulas in this calculator.
5. Is this calculator suitable for AC and DC circuits?
The calculator is suitable for basic electrical calculations using Ohm’s law and standard power formulas. For AC circuits, real power calculations may also require the power factor and other circuit details, particularly with inductive or capacitive loads.