How to Measure Acres of Land: 4 Methods and a Worked Example
To measure acres, find the land's area in square feet and divide by 43,560. For a rectangle, that's length à width á 43,560 in feet, so a 660 à 330 ft field is 217,800 ft², or exactly 5 acres. For an irregular shape, split it into simple pieces, or trace the boundary on a satellite map or with phone GPS.
The right method depends on the shape of the land and how much error you can live with. Here are four, from a tape measure to GPS, with the numbers worked through.
The acre formula
One acre is 43,560 square feet. Which divisor you use depends on the unit you measured in:
| You measured in | Multiply length Ă width, then |
|---|---|
| Feet | á 43,560 |
| Yards | á 4,840 |
| Metres | á 4,046.86 |
An acre has no fixed shape, only a fixed area. It can be a square about 208.7 ft on each side, or a long strip of 66 Ă 660 ft. To get a feel for the size, a US football field including the end zones (360 Ă 160 ft) is about 1.32 acres.
Four ways to measure acres of land
1. Tape or measuring wheel
This is the most direct method for small, simple plots. Measure every side, keep the tape level and pull it tight, then apply the formula. On a four-sided plot that isn't a true rectangle, don't average opposite sides, because that overstates the area when the corners aren't square. Measure a diagonal too and work it out as two triangles. How to calculate the area of irregular land walks through this.
2. Pacing
This gives you a rough number when you have no tools at all. Walk a measured 100 ft and count your steps to find your own pace length, then pace the length and width of the land.
Expect a rough answer. A length error doubles in the area, so if your paces run 5% long, the area comes out about 10% too high. That's fine for judging whether a field is closer to 3 acres or 5, but not for ordering materials.
3. A satellite map
Tap or click each corner on the imagery, and the tool adds up the enclosed area. It's fast, and you can do it from a desk, as long as the boundary is visible from above. See how to measure land area on Google Maps for the steps on a computer.
4. Walking the boundary with GPS
Start recording at one corner, walk the line, and close the shape back at the start. This is the method to use when the edge can't be seen from above, such as uniform grass or scrub. Phone GPS is typically accurate to about 3â5 m under open sky, and worse under trees or near buildings. So it suits a large field better than a small lot.
Which method to use
| Method | Good for | Watch out for |
|---|---|---|
| Tape or wheel | Small rectangles, a yard, a lot | Slow on large land, and curved edges are hard |
| Pacing | A quick rough estimate | Error of 10% or more in the area |
| Satellite map | Any shape with visible edges | Old imagery, tree cover, too few points on curves |
| Phone GPS | Large fields, edges hidden from above | Signal under trees and next to buildings |
Measuring acres on an iPhone or iPad
Field Maps with Area Measure does the last two methods on iPhone and iPad (iOS 17 or later). Tap corners on a satellite map using a magnifier loupe for precise placement, or walk, drive or fly the boundary with GPS and let the app close the shape. It shows area in acres, hectares, square feet, square yards and more, along with the perimeter, and you can save each measurement under a name. GPS tracking and measuring work offline, though a brand-new map area needs a connection to load its imagery. There's no Android version yet. How to measure land area by satellite or GPS covers both techniques in more detail.
Worked example: an irregular field in acres
Say your field is a rectangle with a triangular corner added at one end:
- Rectangle: 400 à 300 ft = 120,000 ft²
- Triangle: base 300 ft, height 150 ft, so 300 à 150 á 2 = 22,500 ft²
- Total: 120,000 + 22,500 = 142,500 ft²
Now convert:
- Acres: 142,500 á 43,560 = 3.27 acres
- Square yards: 142,500 á 9 = 15,833 yd²
- Hectares: 3.27 Ă 0.4047 = 1.32 ha
To budget a job, multiply by the rate on the label. At 3 lb of seed per acre, you'd need 3.27 Ă 3 â 10 lb.
What throws off an acre figure
- Corners that aren't square. Length Ă width only works on a true rectangle. If in doubt, measure a diagonal.
- Slopes. Acreage is normally given as a horizontal area, the way maps express it. On a steady 15% slope, the ground surface is about 1.1% larger, and at 30% it's about 4.4% larger.
- Curved edges. A straight line across a bend cuts off or adds land, so use more points wherever the edge changes direction.
- Fence versus boundary. A fence isn't always on the legal line. Measuring along it tells you what's fenced, not what's deeded.
- Small plots. A few feet of error barely matters on 50 acres, but it matters a lot on a quarter of an acre.
Quick acre conversions
- 1 acre = 43,560 ft² = 4,840 yd² = 4,046.86 m²
- 1 acre â 0.405 ha
- 1 hectare = 10,000 m² â 2.471 acres
- 1 square mile = 640 acres
- ½ acre = 21,780 ft², and Ÿ acre = 10,890 ft²
FAQ
How many feet is an acre?
An acre is an area, so it's measured in square feet: 43,560 ft². As a square, it's about 208.7 ft on each side, or about 835 ft around. Other shapes with the same area have a longer perimeter.
How do I calculate acres from length and width?
Multiply length by width in feet and divide by 43,560. For example, 500 à 200 ft = 100,000 ft², which is about 2.3 acres.
Can I measure acres by walking?
Yes, in two ways. Pacing the sides gives a rough estimate. Walking the boundary with phone GPS gives a better one, because it follows the real shape of the land and adds up the area for you.
Is my measurement good enough for a sale?
It's fine for planning, pricing materials and comparing plots, but it's an estimate. For a sale, a dispute or anything legal, use a licensed surveyor and the official land records.