Electrical Calculators & Conversions

Free Electrical Calculators and Conversion Tools

WireResult provides a complete set of tools to convert watts to amps, calculate energy costs, find the right wire gauge, check voltage drop, and solve Ohm's law problems. Every calculator gives you instant, accurate answers with formulas and step-by-step breakdowns. All results account for voltage, current type (DC/AC), and power factor, which are variables that generic unit converters ignore.

Calculators and Tools

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Watts to Amps

Convert watts to amps at any voltage. Size breakers and wire for appliances, heaters, and equipment.

1500W at 120V 1800W at 240V 3000W at 208V 5000W at 240V

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Amps to Watts

Convert amps to watts at any voltage. Find how much power a circuit delivers and what appliances it can run.

15A at 120V 20A at 240V 30A at 208V 50A at 480V

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kW to Amps

Convert kilowatts to amps for industrial and commercial loads. HVAC, EV chargers, and three-phase equipment.

5 kW at 240V 7.5 kW at 208V 10 kW at 480V 20 kW at 208V

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HP to Amps

Convert single-phase and three-phase AC motor horsepower to running current and NEC Table 430.248 / 430.250 full-load current for branch-circuit sizing.

1 HP at 120V 1/2 HP at 240V 5 HP at 208V 3Φ 10 HP at 480V 3Φ

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Energy Cost

Calculate electricity cost for any appliance. See daily, monthly, and yearly running costs by wattage and rate.

1500W Cost 1200W Cost 3500W Cost 100W Cost

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Voltage Drop

Calculate voltage drop for any wire gauge, amperage, and distance. Check each run against NEC 210.19(A) Informational Note 4's 3% and 5% drop targets.

12AWG 20A 10AWG 30A 8AWG 40A 6AWG 50A

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Wire Size

Find the right wire gauge for any amperage and distance. Copper and aluminum picks against NEC ampacity and the 3% drop target.

20A at 100ft 30A at 150ft 50A at 200ft 100A at 300ft

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Ohm's Law

Enter any two of voltage, current, resistance, or power. Solves for the other two using the power wheel.

120V and 10A 12V and 2A 240V and 20A 24V and 5A

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Formulas

Step-by-step electrical formulas with worked examples. Watts to amps, Ohm's law, voltage drop, and more.

Watts to Amps Ohm's Law Voltage Drop Wire Sizing

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kVA to Amps

Convert kVA to amps for generators, UPS, and transformers. Single-phase and three-phase. Apparent-power current only; source kW ratings are separate manufacturer specs.

5 kVA at 240V 10 kVA at 208V 20 kVA at 480V 50 kVA at 208V

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VA to Watts

Convert a load's VA to watts at any power factor. Load-side real-power calculation for UPS and power-supply sizing.

500 VA to Watts 1000 VA to Watts 1500 VA to Watts 3000 VA to Watts

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mAh to Wh

Convert mAh to Wh for any battery. Check FAA airline limits and compare power bank capacity.

5000mAh 10000mAh 3000mAh 20000mAh

Popular Calculations

arrow_forward1500 Watts to Amps at 120V arrow_forward1800 Watts to Amps at 240V arrow_forward20 Amps to Watts at 120V arrow_forward5 kW to Amps at 240V arrow_forward1 HP Motor Amps at 240V arrow_forward1500W Running Cost arrow_forwardWire Size for 30A at 100ft arrow_forward12 AWG Voltage Drop at 20A, 100ft arrow_forwardOhm's Law: 120V, 10A arrow_forward10 kVA to Amps at 240V arrow_forward1000 VA to Watts arrow_forward5000 mAh to Wh at 3.7V

What Can You Do with These Electrical Calculators?

Convert watts to amps (and back) for DC, single-phase AC, and three-phase AC at any voltage
Size wire gauge to NEC 310.16 ampacity at 60°C, 75°C, or 90°C terminal ratings
Check voltage drop against the 3% branch / 5% total NEC recommendation on long runs
Find motor full-load amps at 120, 208, 240, 277, 460, and 480 V with NEC 430.52 OCP guidance
Calculate kW, kVA, and HP conversions for industrial loads, transformers, and generators
Estimate appliance running costs with country presets for 12 countries
Convert battery capacity from mAh to Wh at any cell voltage for solar, RV, and EV builds
Solve any Ohm's Law combination of voltage, current, resistance, and power
Select line-to-line or line-to-neutral for accurate three-phase results

Frequently Asked Questions

How do I convert watts to amps? expand_more

Divide the wattage by the voltage: Amps = Watts ÷ Volts. For example, 1500 watts at 120 volts is 12.5 amps (DC). For AC circuits, also divide by the power factor: Amps = Watts ÷ (Volts × PF). Use the Watts to Amps Calculator for instant results at any voltage.

What wire size do I need? expand_more

Wire size depends on amperage, distance, source voltage, and termination temperature ratings. Longer runs need thicker wire to stay within the 3% branch-circuit voltage-drop target recommended in NEC 210.19(A) Informational Note 4 (5% total feeder+branch). As a common starting point, 30 amps at 100 feet on a 120V branch circuit is often sized at 8 AWG copper, but the actual pick depends on cable type, ambient and bundling conditions, and local code. Use the Wire Size Calculator for your specific variables.

Why do 240V appliances draw fewer amps than 120V appliances? expand_more

For the same real power, current scales inversely with voltage: Amps = Watts ÷ Volts. A 1,500W space heater draws 12.5 A at 120V but only 6.25 A at 240V, because doubling the voltage halves the current. Lower current generally means less I²R loss in the conductors over the same run length, and often allows a smaller conductor and overcurrent device for the same duty, which is why US dryers, water heaters, EV chargers, and ranges use 240V dedicated circuits. Actual conductor and OCP sizing still depends on the appliance nameplate, cable type, termination temperature, and local code. Use the Watts to Amps Calculator for any wattage.

What is Ohm's Law? expand_more

Ohm's Law defines the relationship between voltage (V), current (I), resistance (R), and power (P). The core formula is V = I × R. Given any two of these four values, you can calculate the other two. Use the Ohm's Law Calculator to solve for any combination.