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LumaQuote Electrical calculators
Electrical Calculators
Free electrical calculators for contractors, estimators and energy auditors. Each one shows the formula with your numbers, works on a phone, and covers single-phase and three-phase.
- Watts to Amps Calculator Current from power, for single-phase, three-phase and DC. Open calculator
- Amps to Watts Calculator Power from current, with power factor. Open calculator
- kVA Calculator kVA from amps, full-load amps and transformer size. Open calculator
- 3 Phase Power Calculator kW, kVA and kVAR from line voltage and current. Open calculator
- Breaker Size Calculator The right breaker for a load, with the 125% rule. Open calculator
- Lighting Circuit Calculator How many fixtures fit on a 15, 20 or 30 A circuit. Open calculator
Which calculator do I need?
- You know the watts and need the current: watts to amps calculator.
- You know the current and need the power: amps to watts calculator.
- You are working with a transformer, generator or UPS: kVA calculator.
- You have a three-phase motor, panel or feeder: 3 phase power calculator.
- You need a breaker for a load: breaker size calculator.
- You are laying out lighting circuits: lighting circuit calculator.
Formulas at a glance
| To find | Single-phase | Three-phase |
|---|---|---|
| Amps from watts | W ÷ (V × PF) | W ÷ (1.732 × V × PF) |
| Watts from amps | V × A × PF | 1.732 × V × A × PF |
| kVA from amps | V × A ÷ 1,000 | 1.732 × V × A ÷ 1,000 |
| Amps from kVA | kVA × 1,000 ÷ V | kVA × 1,000 ÷ (1.732 × V) |
| Breaker for a continuous load | A × 1.25, next size up | A × 1.25, next size up |
V is line-to-line voltage for three-phase. PF is power factor (1.0 for resistive loads). DC: watts = volts × amps.
Lighting calculators
Sizing or retrofitting lighting? These work with the same numbers.
- Lighting layout calculator Fixture count and foot-candles for a room. Open
- High bay lighting calculator Warehouse fixture counts, spacing and savings. Open
- LED retrofit savings calculator Existing vs LED vs LED plus controls. Open
- LED equivalent wattage chart Input watts and LED replacements by fixture type. Open
Quoting lighting work?
LumaQuote is lighting audit and retrofit proposal software for electrical contractors. Count fixtures and take photos on site with the field app, even with no signal, then turn the audit into a priced proposal on your computer.
Free plan, no credit card. iPhone, iPad and Android.
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