Engineering & Electrical calculators
Ohm's law, voltage drop, wire gauge, power, resistors and HVAC.
25 free tools
Most used
BTU CalculatorFind the air conditioner or heater BTU size your room needsOhm's Law CalculatorSolve voltage, current, resistance and power from any two valuesResistor Color Code CalculatorDecode 4, 5 and 6-band resistors — or find the colors for any valueVoltage Drop CalculatorCheck voltage drop and power loss over any wire runWatts, Amps and Volts CalculatorConvert watts to amps, amps to watts, or find volts for DC and ACWire Size CalculatorFind the right AWG wire gauge for your load, distance and voltage
More engineering & electrical tools
Battery Life CalculatorEstimate how long a battery will last from capacity and loadCFM CalculatorWork out the airflow (CFM) a room or exhaust fan needsCircuit Breaker Size CalculatorFind the right breaker size for a load using the 80% continuous ruleConduit Fill CalculatorCheck NEC conduit fill % and how many wires fit in EMT or PVCGear Ratio CalculatorGet gear ratio, output RPM and output torque from tooth countsGenerator Size CalculatorFind the generator wattage you need from running and starting wattsHorsepower CalculatorConvert torque and RPM to horsepower and kW — or solve for torque or RPMkVA and Transformer Size CalculatorConvert kVA to amps (or amps to kVA) and pick a standard transformer sizeLED Resistor CalculatorFind the right current-limiting resistor and wattage for any LEDPipe Flow Rate CalculatorFind pipe flow in GPM or L/min from diameter and velocity — or the reverseSeries and Parallel Resistor CalculatorTotal resistance of any resistors in parallel and in series, instantlyThree-Phase Power CalculatorConvert between kW, kVA, amps and volts for balanced three-phase loadsVoltage Divider CalculatorFind Vout or the resistor you need for any two-resistor dividerBeam Deflection CalculatorMax deflection, bending moment and stress for common beam casesCapacitor CalculatorSeries and parallel capacitance, charge, energy and code decodingDecibel CalculatorConvert power or voltage ratios to dB and add sound levels correctlyDuct Size CalculatorSize round and rectangular HVAC ducts from airflow and velocityPower Factor CalculatorFind power factor, kVA and kvar, and size a correction capacitorRC Time Constant CalculatorTime constant, charge/discharge curve and cutoff frequency of an RC circuit