Volts to Amps Calculator
Convert voltage to current using power (watts) or resistance (ohms). Features unit dropdowns (mV–kV, mW–MW, mΩ–MΩ), automatic wire gauge recommendations, and appliance reference tables.
How to Convert Volts to Amps
Converting volts to amps tells you how much current flows through a circuit at a given voltage—essential information for selecting wire gauge, circuit breakers, and fuses. This calculator supports full unit conversion (mV to kV, mW to MW, mΩ to MΩ) and automatically recommends the appropriate NEC wire gauge for the calculated current.
Pick Method
Choose "Using Watts" if you know the power consumption, or "Using Resistance" for Ohm's Law calculations.
Enter Values with Units
Input voltage (mV/V/kV) and either power (mW/W/kW/MW) or resistance (mΩ/Ω/kΩ/MΩ).
Get Current + Wire Size
Current is shown in amps (and milliamps for small values) with the recommended NEC wire gauge.
Volts to Amps Formula
Example Calculations
A single bulb draws under 1A. Multiple bulbs can share a 15A circuit safely.
Uses 83% of a 15A circuit. NEC requires a 20A circuit for continuous use (80% rule).
Common in automotive and hobbyist circuits. Power consumed: P = 12 × 1.2 = 14.4W.
Standard US electric dryer. Requires a NEMA 14-30 outlet and 10 AWG wiring.
USB Power Delivery at 20V/5A. Standard USB at 5V/2A = 10W max. USB-C PD at 20V delivers 10× more power.
Volts to Amps Conversion Table (Using Power)
| Watts | 5V | 12V | 24V | 120V | 240V | 480V |
|---|---|---|---|---|---|---|
| 10W | 2.00A | 0.83A | 0.42A | 0.08A | 0.04A | 0.02A |
| 50W | 10A | 4.17A | 2.08A | 0.42A | 0.21A | 0.10A |
| 100W | 20A | 8.33A | 4.17A | 0.83A | 0.42A | 0.21A |
| 500W | 100A | 41.67A | 20.83A | 4.17A | 2.08A | 1.04A |
| 1,000W | 200A | 83.33A | 41.67A | 8.33A | 4.17A | 2.08A |
| 1,500W | 300A | 125A | 62.50A | 12.50A | 6.25A | 3.13A |
| 2,000W | 400A | 166.67A | 83.33A | 16.67A | 8.33A | 4.17A |
Wire Gauge Selection Guide (NEC)
| AWG | Max Amps (60°C) | Breaker | Common Use |
|---|---|---|---|
| 14 | 15A | 15A | Lighting, general outlets |
| 12 | 20A | 20A | Kitchen, bathroom, garage |
| 10 | 30A | 30A | Dryers, water heaters, AC |
| 8 | 40A | 40A | Ranges, EV chargers |
| 6 | 55A | 50-60A | Sub-panels, heavy equipment |
| 4 | 70A | 70A | Service entrance, large motors |
| 2 | 95A | 100A | Main service panels |
Common Appliance Current Draw
| Appliance | Watts | Voltage | Amps | Wire/Breaker |
|---|---|---|---|---|
| LED Bulb | 12W | 120V | 0.1A | 14 AWG / 15A shared |
| Phone Charger | 18W | 120V | 0.15A | 14 AWG / 15A shared |
| Laptop | 65W | 120V | 0.54A | 14 AWG / 15A shared |
| Microwave | 1,200W | 120V | 10A | 12 AWG / 20A dedicated |
| Space Heater | 1,500W | 120V | 12.5A | 12 AWG / 20A dedicated |
| Clothes Dryer | 5,400W | 240V | 22.5A | 10 AWG / 30A |
| Electric Range | 9,600W | 240V | 40A | 8 AWG / 50A |
| EV Charger L2 | 9,600W | 240V | 40A | 8 AWG / 50A |
| Central AC | 3,500W | 240V | 14.6A | 10 AWG / 30A |
| Hot Tub | 12,000W | 240V | 50A | 6 AWG / 60A |
⚠️ Electrical Safety & Current Limits
- Dangerous current levels: As little as 10mA (0.01A) across the heart can cause ventricular fibrillation. At 120V with typical skin resistance (1,000-10,000Ω dry), contact can produce 12-120mA—well into the lethal range. Always de-energize circuits before working.
- NEC 80% rule: Continuous loads must not exceed 80% of breaker rating. 15A breaker → 12A max continuous (1,440W at 120V). 20A → 16A (1,920W). 30A → 24A (5,760W at 240V).
- Wire sizing for current: Wire must be rated for the full calculated current. Using undersized wire causes resistive heating, insulation degradation, and fire. Always match wire gauge to breaker rating per NEC Table 310.16.
- GFCI/AFCI protection: Kitchens, bathrooms, outdoors, garages, and laundry areas require GFCI protection (trips at 5mA leakage). Bedrooms require AFCI protection (detects arc faults).
Practical Applications of Volts to Amps Conversion
The volts-to-amps conversion is the gateway calculation for virtually all electrical safety work. Every time you plug in an appliance, charge a device, or flip a switch, Ohm's Law determines how much current flows through the wires behind your walls. Getting this calculation wrong has real consequences: undersized wiring is the leading cause of residential electrical fires in the United States, causing an estimated 45,000 fires and $1.4 billion in property damage annually.
In residential applications, the most common scenario is determining whether an existing circuit can handle a new device. A typical 120V/15A circuit can supply 1,800W total (or 1,440W continuously per NEC). If you're already running a 1,200W microwave and try to add a 1,500W heater on the same circuit, the combined 22.5A far exceeds the 15A rating and will trip the breaker—or worse, could overheat the wiring if the breaker is faulty.
In automotive and solar applications, the lower voltage (12V or 24V) means much higher currents for the same power. A 1,000W car amplifier at 12V draws 83.33A—requiring 4 AWG cable and a proper fuse. This is why solar installations increasingly use higher voltages (48V or even 400V+) to reduce current and allow smaller, less expensive wiring.
For the reverse conversion, use our Amps to Volts Calculator. To convert voltage to power, try our Volts to Watts Calculator. When working with AC circuits, our AC Wattage Calculator lets you calculate real power (W), apparent power (VA), and reactive power (VAR) from voltage and current — including single-phase and three-phase modes. For transformer voltage step-up/down calculations, visit our Transformer Calculator.