Relative Air Density (RAD) is a measure of how much Air is available to be mixed with Fuel and burnt to make the most power.
Too much Air and the mixture is Lean, Too little ait and the mixture is Rich.
Too Rich and the engine runs sluggish, too Lean and possible engine damage awaits.
By being able to compare RAD from one day to another, a Race Engine Tuner can make the necessary adjustments to adapt their tune to a known good setting.
RAD Calc enables you to measure the Air Density and your Jetting then save it for future reference. At a later date, the current Air Density can be compared to a stored setup and suggested Jetting changes considered.
RAD Calc is a Tool to help in your jetting decisions, it still takes some common sense and an understanding of Race Engine Tuning.