Energy is the currency of physics: the capacity to do work, measured in joules, never created or destroyed but constantly converted from one form to another. Work is a force applied through a distance (W = Fd), kinetic energy is the energy of motion (½mv²), gravitational potential energy is the energy of height (mgh), and power is simply the rate at which energy moves (P = E/t, so a watt is a joule per second).
Calculate kinetic energy in joules from mass and velocity (KE = ½mv²).
KE = ½ × m × v²Calculate gravitational potential energy from mass and height (PE = mgh).
PE = m × g × hCalculate mechanical work from force, distance and angle (W = Fd cos θ).
W = F × d × cos(θ)Calculate power from work (energy) and time (P = W/t).
P = W / tConvert watts to joules: calculate energy in joules from power and time (E = P × t).
E = P × tThese are the calculators for questions that are really about capacity or cost: how much energy it takes to lift a load, how much a moving mass is carrying, or how many joules a 2 kW appliance consumes in an hour. They compute ideal figures — a perfect conversion with no losses. Real motors, heaters and batteries shed some fraction as waste heat, so treat the answer as the physical minimum and add the efficiency of your actual device on top.