Free Tool
PLSS Aliquot Acreage Calculator
Click the squares to map out a tract inside a Public Land Survey System section. The tool totals the acreage and writes the aliquot legal description for you — useful whether you own minerals, hold a working interest, or are just reading a deed.
One Section = 640 acres
Quick select a 160-acre quarter:
Selected Acreage
Legal Description
Quick reference: Section = 640 ac • Quarter (NW/4) = 160 ac • Half (N/2) = 320 ac • Quarter-quarter (NW/4 NW/4) = 40 ac
This tool assumes a regular 640-acre section. Always confirm acreage against the official survey plat, especially for sections with government lots.
How the Public Land Survey System works
Across most of the United States, land is described using the Public Land Survey System (PLSS) — a grid of squares laid out from baselines and principal meridians. The building block is the section: a square one mile on each side, containing roughly 640 acres. Thirty-six sections make up a township, a six-mile by six-mile block located by its Township and Range coordinates.
Aliquot parts: how a section gets divided
A section is split into aliquot parts — equal halves and quarters. Quarter the section and each piece is 160 acres (the NW/4, NE/4, SW/4, SE/4). Quarter one of those again and you get a 40-acre quarter-quarter, written like NW/4 NW/4. Read these descriptions right to left: NW/4 SE/4 is the northwest quarter of the southeast quarter.
Why acreage matters to owners
The number of acres you own drives nearly everything else. It feeds your net mineral acres, which in turn determine your division order decimal and the size of every royalty check. If your deed describes your tract in aliquot parts, this tool converts that description into a clean acreage figure in seconds.
Frequently asked questions
How many acres are in a section?
A standard section is one mile square and contains 640 acres. A quarter is 160 acres, a quarter-quarter is 40 acres, and a half is 320 acres.
How do I read an aliquot legal description like NW/4 SE/4?
Read right to left. NW/4 SE/4 means the northwest quarter of the southeast quarter — start with the 160-acre SE quarter, then take its northwest quarter, which is 40 acres.
What do Township and Range mean?
They locate which section you mean. Township is the north-south position of a six-mile block from a baseline; Range is its east-west position from a principal meridian. See the glossary for related terms.
Are all sections exactly 640 acres?
Most are close, but surveying adjustments mean some are not. Sections on the north and west edges of a township often hold irregular government lots whose acreage is on the official plat — don't assume every piece is exactly 40 acres.
This calculator is an educational reference for regular PLSS sections and does not replace a licensed survey, title opinion, or the official plat. Always verify against recorded documents.
Want to save tracts, map multiple sections, or track your acreage over time? See Pro.