One acre is 43,560 square feet. Five acres is 217,800 square feet, a square about 467 feet on a side. Ten acres is a square exactly 660 feet on a side. Twenty acres is commonly 660 by 1,320 feet. Forty acres is a square a quarter mile on a side, 1,320 by 1,320 feet, and walking its boundary is exactly one mile.
Those numbers are fixed. What changes from tract to tract is the shape, and how much of the acreage you can actually use. This page gives the dimensions, some comparisons you can picture, and a realistic look at what fits. It is part of our Oklahoma recreational land guide.
The acre
The National Institute of Standards and Technology defines the acre as exactly 43,560 square feet, which is also 10 square chains or 160 square rods. A surveyor's chain is 66 feet, so an acre is a strip one chain wide and ten chains long, 66 by 660 feet. There are 640 acres in a square mile.
An acre has no required shape. A square acre is about 208.7 feet on a side, but a long strip 100 feet wide and 435.6 feet deep is also one acre.
Dimensions at a glance
| Acres | Square feet | Side if square | Common rectangular shape | Distance around (square) |
|---|---|---|---|---|
| 1 | 43,560 | 208.7 ft | 66 ft x 660 ft | 835 ft |
| 2.5 | 108,900 | 330 ft | 330 ft x 330 ft | 1,320 ft (0.25 mile) |
| 5 | 217,800 | 466.7 ft | 330 ft x 660 ft | 1,867 ft (0.35 mile) |
| 10 | 435,600 | 660 ft | 660 ft x 660 ft | 2,640 ft (0.5 mile) |
| 20 | 871,200 | 933.4 ft | 660 ft x 1,320 ft | 3,734 ft (0.71 mile) |
| 40 | 1,742,400 | 1,320 ft | 1,320 ft x 1,320 ft | 5,280 ft (1 mile) |
| 80 | 3,484,800 | 1,866.8 ft | 1,320 ft x 2,640 ft | 7,467 ft (1.41 miles) |
| 160 | 6,969,600 | 2,640 ft | 2,640 ft x 2,640 ft | 10,560 ft (2 miles) |
All figures are arithmetic from the 43,560-square-foot acre. Side lengths are rounded to the nearest tenth of a foot.
Note the 20-acre row. A 20-acre tract cut as 660 by 1,320 feet has a boundary of 3,960 feet, three quarters of a mile, which is longer than the boundary of a square 20. Long, narrow tracts always have more boundary per acre, which means more fence, more neighbors and more edge.
Why 40, 80 and 160 keep turning up
Most of Oklahoma was surveyed under the Public Land Survey System, the grid of townships and sections. A township is about six miles on a side and contains 36 sections. A section is nominally one mile square and 640 acres. Sections divide by halves and quarters:
- Half section: 320 acres
- Quarter section: 160 acres, half a mile on a side
- Quarter of a quarter: 40 acres, a quarter mile on a side
- Quarter of a quarter of a quarter: 10 acres, 660 feet on a side
That is why rural land is so often sold in 10s, 20s, 40s, 80s and 160s, and why a "40" is a square a quarter mile across. In Oklahoma, everything outside the Panhandle is surveyed from the Indian Meridian and Indian Base Line, whose initial point is near old Fort Arbuckle in Murray County. Legal descriptions are explained in the land-buying glossary and in how to read a survey and plat.
Two cautions. The Bureau of Land Management notes that a section is usually, not always, 640 acres; sections along the north and west edges of a township often run over or under. And tracts in a development are usually laid out to fit roads and terrain, not the grid, so they are rarely perfect squares. The survey, not the round number in the listing, tells you the real acreage and shape.
Comparisons you can picture
A football field, including both end zones, is 360 feet by 160 feet. That is 57,600 square feet, or about 1.32 acres. So:
| Acres | Football fields, end zones included | City blocks 330 ft square |
|---|---|---|
| 1 | About three quarters of one field | 0.4 |
| 5 | 3.8 | 2 |
| 10 | 7.6 | 4 |
| 20 | 15.1 | 8 |
| 40 | 30.3 | 16 |
The "city block" column is only a yardstick: a square 330 feet on a side is 2.5 acres. Real blocks vary from town to town.
Walking gives a better feel than any comparison. At an easy three miles an hour on level ground, the boundary of a square 5 acres takes about seven minutes to walk, a square 10 takes ten minutes, and a square 40 takes twenty. On a wooded mountainside, allow several times that. If you are looking at a tract, walk the lines; see how to walk a property before buying.
What fits
Buildings take up far less room than people expect. The arithmetic:
| Item | Footprint | Share of one acre |
|---|---|---|
| 1,200 sq ft cabin | 1,200 sq ft | 2.8% |
| 30 ft x 40 ft shop | 1,200 sq ft | 2.8% |
| Gravel driveway, 12 ft x 300 ft | 3,600 sq ft | 8.3% |
| Septic installation area (typical minimum) | About 10,000 sq ft | 23% |
| Quarter-acre food plot | 10,890 sq ft | 25% |
A cabin, a shop, a 300-foot driveway and a septic area together use about 16,000 square feet, a little over a third of an acre. On five acres that leaves more than 90% of the tract untouched.
The septic area is the item that sets real minimums. OSU Extension's summary of the state rules, cited on our perc tests and septic systems page, puts the typical minimum lot size for an on-site system at half an acre with public water and three quarters of an acre with a private well, with about 10,000 square feet needed for the system itself. Some system types need more room: a lagoon needs at least 2.5 acres. The soil evaluation decides which type you may install.
5 acres
Room for a cabin or house, a shop, a garden, an RV pad and a good deal of woods between you and the road. A square 5 is about 467 feet across, so a neighbor's house can be within sight when the leaves are down. It is enough for a private weekend place. For hunting, what borders the tract matters more than the five acres themselves.
10 acres
Twice the buffer. A square 10 is 660 feet on a side, which puts a centrally placed cabin 330 feet from every line. There is room for a small food plot or two and a pond site if the terrain allows.
20 acres
Enough to separate uses: a building site near the road, and the back of the tract left alone for wildlife. A 660 by 1,320 foot tract runs a quarter mile deep.
40 acres
A quarter mile square. You can be out of sight and mostly out of earshot of the road, keep a real sanctuary area for deer, and still have several building sites to choose from.
How these sizes work for hunting, including what Oklahoma law says about shooting near roads and buildings, is covered in how many acres you need and managing 10 to 40 acres for deer. Family uses are in 7 things to do on your recreational land.
Deeded acres are not usable acres
The number on the deed is the total area inside the boundary. How much of it you can build on, drive across or plant depends on things the acreage figure does not show:
- Slope. A steep hillside is real acreage and good cover, but it is not a cabin site.
- Drainages and floodplain. Creek bottoms flood. Check the flood map; see flood zones, surveys and title insurance.
- Easements. A road or utility easement across the tract is land you own but cannot build on.
- Rock and soil. Shallow bedrock limits where a septic system and a foundation can go.
- Shape. A long, narrow tract has less usable interior than a square one of the same size.
Two five-acre tracts can have one buildable acre or four. That is one of the main things that separates their prices; see what drives recreational land prices. To judge slope and drainage before you visit, see how to read topo, flood and soil maps.
Price per acre changes with size too
Smaller tracts generally cost more per acre than larger ones in the same area, because the fixed costs of a sale are spread over fewer acres. We show the numbers in how much 5 acres costs in Oklahoma. When you compare a 5 with a 20, compare total price and usable ground, not just the per-acre figure.
Our tracts in Southeastern Oklahoma are surveyed, so the acreage and the corners are established before you buy. Current sizes are on recreational land for sale in Oklahoma and the tracking map.
Frequently asked questions
How big is 5 acres in feet?
Five acres is 217,800 square feet. As a square it is about 466.7 feet on each side, with a boundary of about 1,867 feet. A common rectangular shape is 330 feet by 660 feet. The actual dimensions of any tract depend on how it was surveyed, so check the plat for the real shape.
How many football fields is 10 acres?
About 7.6. A football field with both end zones is 360 by 160 feet, or 57,600 square feet, which is roughly 1.32 acres. Ten acres is 435,600 square feet. Counting only the 300 feet between the goal lines, a field is 48,000 square feet and ten acres is about nine of them.
How long does it take to walk around 40 acres?
A square 40-acre tract is 1,320 feet on each side, so the boundary is 5,280 feet, exactly one mile. On level, open ground at three miles an hour that is a twenty-minute walk. In steep or brushy country it takes much longer, and the boundary of a long, narrow 40 is more than a mile.
How big is a 10-acre square?
Exactly 660 feet on each side, which is one eighth of a mile. The boundary is 2,640 feet, half a mile. In the public land survey grid a 10-acre square is a quarter of a 40-acre quarter-quarter section, which is why 10-acre tracts are so common in rural Oklahoma.
Is 5 acres enough for a house, a shop and a septic system?
In area, easily. A 1,200 square foot cabin, a 30 by 40 foot shop, a 300-foot driveway and a typical septic area together use a little over a third of an acre. What matters is whether the tract has suitable ground: gentle slope, soil that passes a state soil evaluation, and a site outside the floodplain.
Why is land sold in 40-acre and 160-acre pieces?
Because of the Public Land Survey System. It divides land into sections that are nominally one mile square and 640 acres. A quarter section is 160 acres and a quarter of that is 40 acres, a square a quarter mile on each side. Deeds describe land by those divisions, so tracts were historically sold in those sizes.
Sources
- NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement — 1 acre = 43,560 square feet = 10 square chains = 160 square rods; 1 chain = 66 feet; 1 square mile = 640 acres.
- Bureau of Land Management, Land Legal Descriptions — townships of 36 sections, sections usually 640 acres, division into 160-acre and 40-acre parts.
- Oklahoma Historical Society, Encyclopedia of Oklahoma History and Culture, Indian Meridian and Initial Point — the Indian Meridian and Base Line as the reference for all of Oklahoma except the Panhandle; location of the initial point.
- NFL Rulebook, Rule 1, Section 1 — field dimensions of 360 feet by 160 feet. See "Before publishing".
- Blue River Realty, Perc Tests and Septic Systems on Oklahoma Land — typical minimum lot sizes and installation area for on-site sewage systems; lagoon minimum.
- Blue River Realty, How Much Does 5 Acres Cost in Oklahoma? — small-tract price premium.
- Blue River Realty, Flood Zones, Surveys and Title Insurance on Oklahoma Land — flood maps and surveys.
Part of the Oklahoma Recreational Land Guide. Looking for a tract? See recreational land for sale in Oklahoma.