# Electrical Unit Converter

Free electrical unit converter and Ohm's Law calculator. Calculate voltage, current, resistance, and power from any two known values.

## What this calculates

Calculate any electrical value from two known values using Ohm's Law. Enter voltage and resistance, voltage and current, resistance and current, or power and voltage to find all other values.

## Inputs

- **Calculate From** — options: Voltage + Resistance → Current & Power, Voltage + Current → Resistance & Power, Resistance + Current → Voltage & Power, Power + Voltage → Current & Resistance
- **First Value** — min 0 — Voltage (V), Resistance (Ohm), or Power (W) depending on selection
- **Second Value** — min 0 — Resistance (Ohm), Current (A), or Voltage (V) depending on selection

## Outputs

- **Voltage** — formatted as text — Electrical potential difference in volts (V).
- **Current** — formatted as text — Electrical current in amperes (A).
- **Resistance** — formatted as text — Electrical resistance in ohms (Ω).
- **Power** — formatted as text — Electrical power in watts (W).
- **Formulas Used** — formatted as text — The Ohm's Law formulas applied.

## Details

Ohm's Law is the foundation of electrical engineering, relating voltage (V), current (I), resistance (R), and power (P).

Ohm's Law Formulas

- V = I × R (Voltage = Current × Resistance)

- I = V / R (Current = Voltage / Resistance)

- R = V / I (Resistance = Voltage / Current)

Power Formulas

- P = V × I (Power = Voltage × Current)

- P = I² × R (Power = Current² × Resistance)

- P = V² / R (Power = Voltage² / Resistance)

Units

- Voltage: Volts (V)

- Current: Amperes (A)

- Resistance: Ohms (Ω)

- Power: Watts (W)

Common Examples

- US household outlet: 120V, 15A circuit = 1,800W max

- European outlet: 230V, 16A circuit = 3,680W max

- LED bulb: 120V, 0.083A = 10W, resistance ≈ 1,440Ω

## Frequently Asked Questions

**Q: How do I convert watts to amps?**

A: Divide watts by voltage: Amps = Watts / Volts. For example, a 1,500W space heater on a 120V US outlet draws 1,500/120 = 12.5 amps. For a 230V European outlet, the same heater would draw 1,500/230 = 6.5 amps.

**Q: What is Ohm's Law?**

A: Ohm's Law states that the current through a conductor is directly proportional to the voltage and inversely proportional to the resistance: V = I × R. It was formulated by Georg Simon Ohm in 1827 and is the fundamental law of electrical circuits.

**Q: How many watts can a 15-amp circuit handle?**

A: A 15-amp circuit at 120V can theoretically handle 1,800 watts (15A × 120V). However, the National Electrical Code recommends loading circuits to only 80% capacity for continuous loads, so 1,440 watts is the practical safe maximum.

**Q: Why is P = I²R but also P = V²/R?**

A: Both are derived from P = V×I using Ohm's Law. Substituting V = IR gives P = (IR)×I = I²R. Substituting I = V/R gives P = V×(V/R) = V²/R. All three power formulas give the same result; use whichever one matches your known values.

---

Source: https://vastcalc.com/calculators/conversion/electrical-unit-converter
Category: Conversion
Last updated: 2026-04-21