The equation for the law of conservation of energy is as follows:

KEi + PEi = KEf + PEf

You may also find the equation written as follows:

KEi + PEgi + PEsi = KEf + PEgf + PEsf

KEi - Initial Kinetic Energy
PEi - Initial Potential Energy
KEf - Final Kinetic Energy
PEf - Final Potential Energy
KEi - Initial Kinetic Energy
PEgi – Initial gravitational potential energy (if height is involved)
PEsi – Initial Elastic Potential Energy
KEf - Final Kinetic Energy
PEgf – Final Gravitational Energy (if height is involved)
PEsf – Final Elastic Potential Energy