Watt Calculator — Electrical Power from V, I, R
Find the power consumed by any electrical component. Enter any two of voltage (V), current (I) or resistance (R) and this calculator derives the power in watts plus the missing quantity — using P = V × I, P = V²/R or P = I²R.
V
A
Ω
Electrical power dissipated (P = V × I)
- 1
Resistance (R = V ÷ I)
12 ÷ 2 = 6 - 2
Power (P = V × I)
12 × 2 = 24
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Power (W) = Voltage (V) × Current (A). Also: P = V²/R or P = I²×R. Enter any two of V, I, R and get the third plus power. Default example: 12 V × 2 A = 24 W (resistance = 6 Ω). All three formulas are equivalent via Ohm's law V = I × R.
Formel
How this is calculated
Electrical power is the rate at which energy is transferred or dissipated in a circuit, measured in watts (W). The three equivalent power formulas all stem from combining P = V × I with Ohm's law (V = I × R). If you know voltage and current, use P = V × I directly. If you know voltage and resistance, substitute I = V/R to get P = V²/R. If you know current and resistance, substitute V = I × R to get P = I²R.
This calculator reads whichever two fields you fill in and solves for the third before computing power. For example, a 240 V appliance drawing 10 A consumes 2 400 W (2.4 kW). A 100 Ω resistor with 5 V across it dissipates 25 mW (0.025 W).
The formulas assume a purely resistive DC (or equivalent AC) load at steady state. For AC circuits with reactive loads — capacitors, inductors, motors — the apparent power in volt-amperes (VA) differs from real power in watts by the power factor. Non-ohmic devices such as LEDs or transistors may not follow simple Ohm's law exactly at all operating points.
Ofte stillede spørgsmål
P = V × I = 240 × 5 = 1 200 W (1.2 kW). This is exactly how electricity meters work — kilowatt-hours are calculated by multiplying power in kW by time in hours.
Watts measure real power — energy actually converted to heat, light or mechanical work. Volt-amperes measure apparent power — the product of RMS voltage and RMS current. For purely resistive loads they are equal. For reactive loads (motors, transformers), apparent power is higher; the ratio of real to apparent power is the power factor (0–1).
Power = Voltage × Current. Since mains voltage is fixed, reducing current reduces consumption. Practical steps: replace high-wattage bulbs with LED equivalents, choose appliances with higher energy efficiency ratings, and turn off standby loads. A plug-in watt-meter lets you measure the actual consumption of individual devices.
Også kendt som
TG we-Calculate Editorial Team. (2026). Watt Calculator — Electrical Power from V, I, R [Online calculator]. TG we-Calculate. https://we-calculate.com/da/calculator/watt-calculator
TG we-Calculate Editorial Team. "Watt Calculator — Electrical Power from V, I, R." TG we-Calculate. 2026. https://we-calculate.com/da/calculator/watt-calculator.
TG we-Calculate Editorial Team, "Watt Calculator — Electrical Power from V, I, R," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/da/calculator/watt-calculator
@misc{wecalculate_watt_calculator, title = {Watt Calculator — Electrical Power from V, I, R}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/da/calculator/watt-calculator}}, year = {2026}, note = {TG we-Calculate} }
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