Pretty close to 予定 (よてい) in meaning, but perhaps more elaborate - you'd use 計画 to say "I have a plan to get rich!" or to say "I planned out our whole vacation to 3 countries." . . but you wouldn't use 予定。
(FP)
計 (measure) + 画 (a drawing)
= 計画 (plan)
余計な
( よけい な)
excessive, uncalled-for, and unnecessary (usually used in the context of 余計なお世話だよ! (よけいなおせわだよ!): 'Mind your own business!')
余 (excess) + 計 (measure)
= 余計 (uncalled-for)