science

Electrical Power Calculator

Electrical power calculator: solve any two of P = VI to find the third, plus daily energy use (kWh) and monthly electricity cost estimates.

Free online · Instant results

Known quantities (pick any two)

Voltage (V)

Resistance (Ω)

Voltage

220 V

Current (solved)

2.2 A

Resistance

100 Ω

Power (solved)

484 W

Solution steps

1Known: V = 220 V, R = 100 Ω
2V = 220 V, I = 2.2 A
3R = 100 Ω, P = 484 W
4Verified: V = I × R and P = V × I

Energy note: running 1 hour consumes 0.484 kWh; at 0.55 CNY/kWh that's ≈ 0.266 CNY/hour.

Ohm's law wheel (12 formulas)

Solve for	From I,R	Alt 1	Alt 2
V =	I × R	P / I	√(P × R)
I =	V / R	P / V	√(P / R)
R =	V / I	V² / P	P / I²
P =	V × I	I² × R	V² / R

💡 Ohm's law applies to ohmic (resistive) devices. Motors, LEDs and switching power supplies are non-linear — their effective resistance changes with voltage.

Frequently Asked Questions

How much electricity does a 100W device use per day?▼

100W × 24h = 2400Wh = 2.4 kWh. Monthly cost = 2.4 × 30 × your electricity rate.

How do I use the Ohm's Law Calculator?▼

Open the page and fill in the input fields — results update automatically. V=IR — solve any two of voltage, current, resistance.

Are the results accurate?▼

Yes. Standard formulas and conversion factors are used and verified.

Is it free? Do I need to sign up?▼

Completely free. No registration, login or download required.

Does it work on mobile?▼

Yes. The responsive design works on phones, tablets and desktops.

💡

This is a dedicated variant of the Ohm's Law Calculator, pre-configured for this scenario with tailored FAQs.