Beware of well intended but wrong answers to this question!
I say that because you need to start with "what is the highest and best use" of the land in question. Is it residential, commercial, industrial, etc. Is it in an area that is subject to transition (soon to be commercial)?
Another thing is assuming it is residential, the main value in the land is the ability to build a home on it. If the zoning only allows one dwelling per acre it is at it's highest and best use. If it is 1.75 acres, you can't split the extra .75 acres so it adds very little additional value. If it is 2 acres but you can't split it, it is not worth 2x the price of a one acre parcel!
In premium properties, they sell by the "frontage foot" (i.e. X feet of frontage on the highway, or on the lake).
Real estate is not a commodity so you can't sell it by the sq. ft. or per acre without a lot of additional compensating factors.
Best of luck from Boise! I hope you found this answer helpful!