Watts to Volts
Watts Amps Volts Definition
Watts (W) — Electrical Power
A watt (W) is the unit of electrical power. One watt equals one joule (J) of energy transferred per second. Watts measure how fast electrical energy is consumed or produced. A 60 W light bulb consumes 60 joules of energy every second. Power in watts equals voltage in volts (V) multiplied by current in amps (A): P(W) = V(V) × I(A).
Volts (V) — Electrical Pressure
A volt (V) is the unit of electrical potential difference, or voltage. Voltage drives current through a circuit. A standard US wall outlet supplies 120 V, while European outlets supply 230 V. Higher voltage pushes more current through a given resistance. Voltage in volts equals power in watts (W) divided by current in amps (A): V(V) = P(W) ÷ I(A).
Amps (A) — Electrical Current
An ampere (A), or amp, is the unit of electrical current. Current measures the flow rate of electric charge through a conductor. A typical household circuit carries 15 A or 20 A. Current in amps equals power in watts (W) divided by voltage in volts (V): I(A) = P(W) ÷ V(V).
Interactive Power Triangle
Hover over each part of the formula to see what it represents.
P = V × I Watts Amps Volts Diagram
The power triangle is a visual tool used in electrical engineering to show the relationship between power (P), voltage (V), and current (I). Cover any one variable to see the formula for calculating the remaining value. This relationship is based on Watt's Law: P = V × I.
Voltage (V)
Electrical pressure that pushes current through the circuit. Measured in volts.
Current (I)
Flow rate of electric charge through a conductor. Measured in amps (A).
Power (P)
Rate of energy transfer in the circuit. Measured in watts (W). P = V × I.
Resistance (R)
Opposition to current flow. Measured in ohms (Ω). V = I × R.
Interactive Circuit Diagram
Hover over a component to learn its role
How to Convert Watts to Volts
To convert watts to volts, divide power (W) by current (A) for DC circuits. For AC circuits, also divide by the power factor (PF). The Watts to Volts conversion formula changes for single phase and three phase AC circuits. Use V = √(P × R) to convert watts to volts using resistance when current is unknown.
Watts Volts Amps Formula
There are 3 core formulas connecting watts, volts, and amps. These formulas derive from Watt's Law and Ohm's Law:
V = P ÷ I Voltage = Power ÷ Current
V = P ÷ (PF × I) Voltage = Power ÷ (Power Factor × Current)
V = P ÷ (√3 × PF × I) Voltage = Power ÷ (√3 × Power Factor × Current)
Formula Breakdown
Hover over each part of the formula to see what it represents.
Volts = Watts ÷ Amps
Using Resistance
DC Watts to Volts Calculation
Direct current (DC) circuits use the simplest watts to volts formula
DC watts to volts conversion uses the formula V(V) = P(W) ÷ I(A). Direct Current (DC) flows in one constant direction — batteries, solar panels, and power supplies produce DC power. The DC watts to volts formula does not require a power factor because DC has no reactive power component.
V(V) = P(W) ÷ I(A) Voltage in volts = Power in watts ÷ Current in amps
A 12 V DC battery powers a 60 W device. The current draw is 60 W ÷ 12 V = 5 A. Working in reverse: V = 60 W ÷ 5 A = 12 V.
Try It — DC Watts to Volts
Enter watts and amps to see the voltage
AC Watts to Volts Calculation
AC conversions require a power factor (PF) because not all power is used effectively
Single Phase
AC single phase watts to volts conversion uses V(V) = P(W) ÷ (PF × I(A)). Single phase AC power is standard in residential wiring — homes, offices, and small appliances run on single phase. The power factor (PF) ranges from 0 to 1 and represents how effectively the circuit uses power. A PF of 1 means 100% of the power is used; typical residential power factors range from 0.8 to 0.95.
V(V) = P(W) ÷ (PF × I(A)) Voltage = Power ÷ (Power Factor × Current)
AC Waveform
Three Phase
AC three phase circuits supply power through 3 alternating currents, offset by 120° from each other. Three phase power is used in industrial equipment, large motors, and commercial power distribution networks. The watts to volts formula for three phase depends on whether the measurement is line-to-line or line-to-neutral voltage.
Calculation with Line to Line Voltage
V(V) = P(W) ÷ (√3 × PF × I(A)) Line-to-line voltage is measured between any 2 phase conductors. Use this for motor loads and three-phase equipment. √3 ≈ 1.732.
Calculation with Line to Neutral Voltage
V(V) = P(W) ÷ (3 × PF × I(A)) Line-to-neutral voltage is measured between a phase conductor and the neutral point. Use this for single-phase loads connected to a three-phase panel.
Convert Watts to Volts using Resistance
Use this formula when current is unknown but resistance is available
Convert watts to volts using resistance with the formula V(V) = √(P(W) × R(Ω)). This formula combines Watt's Law and Ohm's Law. Use this watts to volts conversion when a multimeter reads resistance instead of current. This formula applies to both DC and AC circuits.
Watts Voltage Resistance
The relationship between watts, voltage, and resistance follows from combining P = V × I and V = I × R (Ohm's Law). Substituting gives P = V² ÷ R, which rearranges to V = √(P × R).
V = √(P × R) Voltage = Square root of (Power × Resistance)
A 100 W heater with 144 Ω resistance: V = √(100 × 144) = √14400 = 120 V.
Ohm's Law Triangle
Click a variable to isolate its formula
V = I × R
Combined with Watt's Law: V = √(P × R)
Watts to Volts Conversion Chart
Quick reference table for DC circuits at common current values
| Power (W) | @ 1 A | @ 5 A | @ 10 A | @ 15 A | @ 20 A |
|---|---|---|---|---|---|
| 10 W | 10 V | 2 V | 1 V | 0.6667 V | 0.5 V |
| 25 W | 25 V | 5 V | 2.5 V | 1.6667 V | 1.25 V |
| 50 W | 50 V | 10 V | 5 V | 3.3333 V | 2.5 V |
| 100 W | 100 V | 20 V | 10 V | 6.6667 V | 5 V |
| 150 W | 150 V | 30 V | 15 V | 10 V | 7.5 V |
| 200 W | 200 V | 40 V | 20 V | 13.3333 V | 10 V |
| 300 W | 300 V | 60 V | 30 V | 20 V | 15 V |
| 500 W | 500 V | 100 V | 50 V | 33.3333 V | 25 V |
| 750 W | 750 V | 150 V | 75 V | 50 V | 37.5 V |
| 1k W | 1,000 V | 200 V | 100 V | 66.6667 V | 50 V |
| 1.5k W | 1,500 V | 300 V | 150 V | 100 V | 75 V |
| 2k W | 2,000 V | 400 V | 200 V | 133.3333 V | 100 V |
| 3k W | 3,000 V | 600 V | 300 V | 200 V | 150 V |
| 5k W | 5,000 V | 1,000 V | 500 V | 333.3333 V | 250 V |
| 10k W | 10,000 V | 2,000 V | 1,000 V | 666.6667 V | 500 V |
Our Electrical Calculators
Free online tools for engineers, students, and professionals
Watts to Volts Calculator
Convert power (W) to voltage (V) for DC, AC single-phase, and AC three-phase circuits.
Watts Volts Amps Ohms Calculator
Calculate any 2 unknown electrical values from Resistance, Current, Voltage, and Power.
Watts to Electron Volts Converter
Convert energy between watt-seconds, watt-hours, and electron volts (eV).
Frequently Asked Questions
What does a Watt measure?
A watt (W) measures electrical power — the rate at which electrical energy is consumed or produced. One watt equals one joule of energy per second. A 100 W light bulb uses 100 joules of electrical energy every second. Watts are named after James Watt, the Scottish inventor. Watts are calculated by multiplying volts (V) by amps (A): P(W) = V(V) × I(A).
How many Volts are in a Watt?
There is no fixed number of volts in a watt because volts and watts measure different things — volts measure electrical pressure, watts measure electrical power. The relationship between watts and volts depends on the current (amps): V(V) = P(W) ÷ I(A). For example, 100 watts at 10 amps equals 10 volts, but 100 watts at 1 amp equals 100 volts.
Can Watts be converted to Volts?
Yes, watts can be converted to volts when you know either the current (amps) or the resistance (ohms). Using current: V = P ÷ I. Using resistance: V = √(P × R). Without at least one additional value, watts cannot be converted to volts because they measure different electrical properties.
How Many Volts is 100 Watts?
100 watts equals different voltages depending on the current. At 1 A, 100 W = 100 V. At 5 A, 100 W = 20 V. At 10 A, 100 W = 10 V. At 20 A, 100 W = 5 V. The formula is V = 100 W ÷ I(A). For a standard 120 V US circuit, 100 watts draws 0.83 A of current.
What is the difference between DC and AC circuits?
DC (Direct Current) flows in one constant direction — batteries, solar panels, and USB chargers produce DC power. AC (Alternating Current) periodically reverses direction at 50 Hz or 60 Hz — wall outlets and the power grid supply AC power. The watts to volts formula for DC is V = P ÷ I. AC circuits require a power factor (PF) in the formula: V = P ÷ (PF × I) for single phase.
Can I convert watts to volts without knowing the current?
Yes, convert watts to volts without current by using resistance. The formula is V = √(P × R), where P is power in watts and R is resistance in ohms. Measure resistance with a multimeter. For example, a 100 W load with 400 Ω resistance: V = √(100 × 400) = √40000 = 200 V.
What is a Power Factor?
Power factor (PF) is a number between 0 and 1 that measures how effectively an AC circuit uses electrical power. A PF of 1 means all supplied power is used as real power. A PF of 0.8 means 80% is real power and 20% is reactive power. Typical power factors: resistive loads (heaters, incandescent bulbs) have PF ≈ 1.0; motors and compressors have PF = 0.7 to 0.9; LED drivers have PF = 0.5 to 0.95. Power factor only applies to AC circuits — DC circuits have no reactive power.
When should I use line-to-line vs line-to-neutral Voltage?
Use line-to-line voltage when measuring between any 2 of the 3 phase conductors — this applies to three-phase motors, industrial equipment, and large HVAC systems. Common line-to-line voltages: 208 V, 480 V, 600 V. Use line-to-neutral voltage when measuring between a single phase conductor and the neutral wire — this applies to single-phase loads on a three-phase panel, lighting circuits, and receptacles. Common line-to-neutral voltages: 120 V, 277 V, 347 V.