Physics and Engineering

  • Watt's Law Calculator
    Free Watt's Law calculator. Solve for power (P), voltage (V), or current (I) using P = V × I. Enter any two values to find the third instantly.
  • Electricity Units to kWh Calculator
    Convert electricity units to kilowatt-hours (1 unit = 1 kWh) and estimate your bill cost from units consumed and your per-unit tariff.
  • Space Heater Running Cost Calculator
    Calculate the running cost of an electric space heater per hour, day and month from wattage, hours used and your electricity rate per kWh.
  • Monthly Electricity Cost from Watts Calculator
    Calculate the monthly electricity cost of any device from its wattage, daily usage hours and your per-kWh rate. Get daily, monthly and yearly estimates.
  • Motor Torque from kW and RPM Calculator
    Calculate electric motor torque in newton-metres from power (kW) and speed (RPM) using T = 9549 x kW / RPM. Includes lb-ft conversion.
  • Battery Discharge Time Calculator
    Estimate how long a battery will last from its amp-hour capacity, load current, and usable depth of discharge. Free runtime calculator: t = (Ah × DoD) / A.
  • kWh from Amps, Volts and Hours Calculator
    Calculate electricity usage in kWh from amps, volts and hours. Enter current, voltage and run time to get energy used, power in watts and cost.
  • Electricity Bill Calculator
    Estimate your electricity bill from units consumed (kWh), the per-unit rate, and any fixed charge. Free, fast, and works with any currency.
  • Power from Torque and RPM Calculator
    Calculate mechanical power in kW, watts and horsepower from torque (N·m) and rotational speed (RPM) using P = T × RPM / 9549.
  • Time to Fill Tank Calculator
    Calculate how long it takes to fill a tank from its volume and water flow rate using t = V / Q. Supports liters, gallons, m3, and multiple flow units.
  • Gas Density Calculator
    Calculate the density of an ideal gas from pressure, molar mass, and temperature using ρ = PM/(RT). Free, instant results in kg/m³ and g/L.
  • EV vs Gas Cost per Mile Calculator
    Compare the cost per mile of driving an electric vehicle versus a gas car. Enter kWh/mile, electricity price, gas price, and MPG to see your savings.
  • Electricity Usage From Meter Reading Calculator
    Calculate kWh used between two electricity meter readings. Enter current and previous readings plus a meter multiplier to get usage and estimated cost.
  • EV kWh per 100 km Calculator
    Calculate your electric vehicle energy consumption in kWh per 100 km from the energy used and distance driven. Get km/kWh and Wh/km too.
  • Milliamps to Amps Calculator
    Convert milliamps (mA) to amps (A) instantly. Enter a current in mA and get the value in amperes using A = mA / 1000.
  • kWh to BTU Calculator
    Convert kilowatt-hours (kWh) to British Thermal Units (BTU) instantly. Enter kWh and get BTU using the factor 1 kWh = 3412.142 BTU.
  • Amps to Milliamps Calculator
    Convert amps (A) to milliamps (mA) instantly. Enter a current value in amperes and get the equivalent in milliamps using mA = A × 1000.
  • Battery Amp-Hours Needed Calculator
    Calculate the battery amp-hours (Ah) needed from watts, runtime hours and voltage. Includes depth-of-discharge adjustment for any 12V, 24V or 48V battery.
  • Water Flow Rate Through a Hose Calculator
    Estimate water flow rate through a hose from inner diameter, supply pressure and discharge coefficient. Get liters/min, GPM and exit velocity instantly.
  • Atmospheric Pressure at Altitude Calculator
    Compute atmospheric pressure at a given altitude using the barometric formula with sea-level pressure, temperature, and the standard lapse rate.
  • Reynolds Number for Pipe Flow Calculator
    Calculate the Reynolds number for fluid flow in a pipe from density, velocity, diameter and viscosity. Re = ρvD/μ. Find if flow is laminar or turbulent.
  • Velocity Head Calculator
    Calculate velocity head (hv = v²/2g) from flow velocity and gravity. Free fluid dynamics tool for pipe flow, Bernoulli and head loss analysis.
  • Specific Gravity Calculator (Fluids)
    Calculate the specific gravity of a fluid from its density and a reference water density using SG = ρ_fluid / ρ_water. Free, instant, and accurate.
  • Battery State of Charge Calculator
    Estimate battery State of Charge (SOC %) from a measured voltage reading using linear interpolation between empty (Vmin) and full (Vmax) voltages.

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