Acreage · Sections · Measuring land · October 19, 2026

How Big Is 40 Acres? Feet, Football Fields and Maps

How big is 40 acres? As a square, 1,320 feet (a quarter mile) on a side, about 30 football fields. Other shapes, metric and how to see a forty on a map.

How big is 40 acres? Laid out as a square, 40 acres is 1,320 feet on each side, which is exactly a quarter mile. That is 1,742,400 square feet, one-sixteenth of a square mile, or a bit over 16 hectares. In the township and range states it is also a very familiar shape: the quarter-quarter section, the “forty” that shows up on plat books and county parcel maps all over the Midwest and West. Below are the numbers, a few ways to picture it, the shapes a forty can take and how to see one on a map.

The short answer

Area: 40 × 43,560 = 1,742,400 square feet, or about 193,600 square yards.
As a square: 1,320 × 1,320 feet, a quarter mile on each side.
Perimeter of that square: 5,280 feet, so walking around a square forty is a one-mile walk.
Football fields: about 30 with end zones, or about 36 counting only the 100-yard playing field.
Metric: about 16.19 hectares, or 0.162 square kilometers; a square forty is about 402 meters on a side.
Square miles: 0.0625, which is 1/16 of a square mile.

The math behind 40 acres

One acre is 43,560 square feet, the U.S. standard. Multiply by 40 and you get 1,742,400 square feet. The square root of that is 1,320, so a perfectly square 40 acres measures 1,320 feet by 1,320 feet. Since a mile is 5,280 feet, each side is one quarter of a mile, and four sides add up to one full mile.

The same figures work the other way. A square mile holds 640 acres, so 40 acres is 640 ÷ 16. That is no accident: the federal survey grid was built in miles and then split into quarters and quarters again, and the forty is what you get after two rounds of quartering. Our guide to how many acres in a section lists every step of that split.

Ways to picture 40 acres

Football fields. A football field with both end zones is 360 by 160 feet, or 57,600 square feet. Dividing 1,742,400 by that gives 30.25 fields. Without the end zones, 300 by 160 feet, it is about 36.
A quarter-mile walk. Each side of a square forty is the length of one lap around a standard running track, give or take a few feet.
Driving past it. At 30 miles an hour, a car covers a quarter mile in 30 seconds, so a square forty along a rural road takes about half a minute to pass.
Walking around it. At a steady 3 miles an hour, walking the one-mile boundary of a square forty takes about 20 minutes on flat, open ground. Fences, brush and creeks add a lot.
Building lots. Forty acres equals 160 quarter-acre lots on paper, but streets, setbacks and drainage take a large share in a real subdivision. See how many lots per acre for why the usable count is lower.

Not every forty is a square

Forty acres can come in any shape, and the dimensions change a lot. A few common layouts with the same area:

1,320 × 1,320 feet: the classic square quarter-quarter section.
660 × 2,640 feet: an eighth of a mile wide and half a mile long, often the result of splitting an 80 down the middle the other way.
330 × 5,280 feet: a long strip 1/16 mile wide and a full mile deep, the kind of shape that turns up along roads and rivers.
Irregular tracts: metes-and-bounds parcels, lots along a lake or curving road, and leftovers from older divisions can be any shape at all.

The narrower the shape, the longer the fence line. A square forty needs about one mile of perimeter fence, while the 660 × 2,640 rectangle needs about 1.25 miles and the 330 × 5,280 strip about 2.1 miles, all for the same 40 acres.

The “forty” in township and range descriptions

In the 30 public land states, a legal description such as “NW 1/4 of the NE 1/4 of Section 12” describes one quarter-quarter section, nominally 40 acres. These pieces are called aliquot parts, and much of rural land has been bought and sold in forties, eighties and quarter sections for generations. If you see a parcel described this way, our guide to quarter sections shows how to read the fractions from right to left.

Nominal is the key word. Sections on a township’s north and west sides, sections touched by lakes or rivers and areas with old survey errors can hold more or less than 640 acres. Those odd-sized pieces are often mapped as numbered government lots instead of forties, and a lot described as “Lot 2” may be 36 acres or 44 acres. Always check the acreage on the deed, plat or survey rather than assuming a perfect 40.

How to see 40 acres on a map

Open a county parcel viewer. Our land map links to free county GIS sites. In township and range country, the section grid often shows as faint lines, and forties appear as squares about a quarter mile across.
Use the measure tool. Most viewers have an area tool. Trace the parcel and compare the result with the acreage in the parcel pop-up.
Check the scale. Zoom until the scale bar shows a quarter mile; a square forty should be about one bar-length on each side.
Remember the limits. GIS parcel lines are drawn for tax mapping and can be off by many feet. For the real boundary, see how to find the acreage of a property, and hire a licensed surveyor when it matters.

If you are walking the ground instead, our guide to measuring an acre of land covers pacing, measuring wheels and mapping apps, and the same methods scale up to a forty.

40 acres next to other common sizes

1 acre: about 208.7 feet square.
5 acres: about 466.7 feet square, or 660 × 330 feet as an aliquot piece.
10 acres: 660 × 660 feet as a quarter of a forty.
20 acres: half a forty, 1,320 × 660 feet.
40 acres: 1,320 × 1,320 feet.
80 acres: two forties, 1,320 × 2,640 feet.
160 acres: a quarter section, half a mile square.

Questions people ask

How many feet is 40 acres on each side?

1,320 feet if it is square, which is a quarter mile. Other shapes hold the same area, such as 660 by 2,640 feet.

How many football fields is 40 acres?

About 30 counting the end zones, since a full field is 360 by 160 feet, and about 36 counting only the 100-yard playing field.

How many square miles is 40 acres?

0.0625 square miles, or one-sixteenth of a square mile. A square mile holds 640 acres.

How many square feet is 40 acres?

1,742,400 square feet, which is 40 times the 43,560 square feet in one acre.

What is a quarter-quarter section?

In the township and range system it is a quarter of a quarter section, nominally 40 acres, written like NW 1/4 NE 1/4. Pieces along township edges or water can be larger or smaller and are often mapped as lots.

How long does it take to walk around 40 acres?

A square forty has a one-mile boundary, so about 20 minutes at a steady 3 miles an hour on open ground. A long, narrow forty has a much longer boundary.