Circuits & Power

Ohm’s law, power, energy, running costs and three-phase supplies.

• Cable Power Loss Calculator Power wasted as heat in a cable run, the efficiency it costs you, and what that energy is worth over a year.
• Electricity Cost Calculator What an appliance costs to run — per day, month and year — from its wattage, hours of use and your unit rate.
• kWh Calculator — Energy Use and Cost Converts watts and hours into kilowatt-hours, and works out what that energy costs over a day, a month and a year.
• Motor Power and Efficiency Calculator Electrical input power, current draw and losses for a motor from its shaft output, efficiency and power factor.
• Ohm's Law Calculator Enter any two of voltage, current, resistance and power, and get the other two — with the formula used shown.
• Power Factor Calculator Power factor, real, apparent and reactive power for a single-phase supply, plus the correction capacitance needed.
• Three-Phase Power Calculator Real, apparent and reactive power for a balanced three-phase load, with line and phase voltages.
• Transformer Sizing Calculator (kVA) The kVA rating a transformer needs for a given load, with growth headroom and the current on each winding.
• Transformer Turns Ratio Calculator Turns ratio from primary and secondary voltages, with the secondary winding turns and the current relationship.
• Voltage Drop Calculator Voltage lost along a cable run — from conductor area, length and current, for copper or aluminium.
• Wire Gauge Calculator — Size for Voltage Drop Conductor size needed to hold a cable run within a voltage drop limit, in mm² and AWG. Voltage drop only — not an ampacity or code check.