How to Measure an Acre

Method 1

Google Maps measure-distance tool

The Google Maps measure-distance tool is the most accessible free method for estimating land area. Open Google Maps in a desktop browser, right-click on the starting corner of the area you want to measure, and select "Measure distance" from the context menu. Click each subsequent corner around the perimeter. Google Maps automatically closes the polygon when you click back to the start, and shows the enclosed area in square feet, square metres, square miles, and (for areas above one hectare) hectares. To convert to acres, divide square feet by 43,560 or square metres by 4,046.86.

The accuracy of Google Maps measurement depends on three factors. First, the satellite imagery resolution at your location determines how precisely you can identify property corners. Imagery is typically 1 to 4 metres per pixel in suburban US areas, falling to 0.5 metres per pixel or better in dense urban metros and rising to 5 to 10 metres per pixel in remote rural areas. Second, the imagery date matters. Google Maps imagery is typically refreshed every 1 to 3 years in urban areas and every 5 to 10 years in rural areas. Recent construction, fences, hedgerows, or land clearing may not be visible. Third, the slope of the ground is not corrected. Areas measured on flat satellite imagery are projected to a horizontal plane, so a steep slope appears smaller than its actual surface area.

For typical residential parcels of 0.25 to 5 acres on relatively flat ground with clear property markers visible in the imagery, Google Maps measurement is accurate to within 5 to 10 percent. For larger parcels with clear boundaries (a fence line, a road, a treeline), accuracy can reach 2 to 4 percent. For irregularly shaped parcels with no visible boundaries, accuracy can degrade to 15 to 30 percent. The tool is excellent for getting a quick sense of a parcel's size before a real-estate showing, for planning a garden layout, or for any context where 10 percent accuracy is good enough.

Method 2

Smartphone GPS apps for area measurement

For measuring a parcel by walking the perimeter, several smartphone apps use the device's GPS receiver to record your path and compute the enclosed area. Popular options include GPS Fields Area Measure (free with ads, $5 ad-free, both Android and iOS), Map My Acreage (iOS, $4 one-time), Acreage by Cherokee Industries ($30 per year, for surveyors and field workers), and the agricultural-focused FieldMargin (free with paid subscription tier).

The workflow is straightforward. Open the app, set a starting waypoint at one corner of the property, walk the perimeter (or drive it on a UTV or pickup) while the GPS records your track, and close the polygon at the starting corner. The app shows the enclosed area in your chosen units. Most apps support exporting the GPS track to KML or GPX format for use in other mapping software.

Smartphone GPS accuracy is typically 3 to 10 metres horizontal in good conditions (clear sky, recent satellite fix), degrading to 10 to 30 metres in dense forest, deep canyons, or under heavy cloud cover. For a 1-acre parcel measured by walking the boundary, typical accuracy is 3 to 7 percent of the true area. The accuracy improves substantially with longer perimeters because GPS errors tend to average out over distance. A 10-acre parcel walked carefully with a smartphone GPS typically measures within 1 to 3 percent of the surveyed area.

The advantage of this method over Google Maps is that you are physically walking the actual property boundary, not estimating from a satellite image that may not show the true legal boundary. The disadvantage is the time required: walking a 5-acre perimeter at a careful surveying pace takes 30 to 45 minutes, plus any time to navigate around trees, fences, or other obstacles that prevent following the exact boundary line.

Method 3

The 209-foot pacing method

One acre laid out as a square measures 208.71 feet on each side. For a no-tech in-the-field check, you can pace out a 209-foot square and confirm whether your actual parcel is larger or smaller than the resulting area. The technique requires only a known step length and a straight-edge reference (a road, a fence line, a treeline) to align against.

First, calibrate your step length. Walk 100 feet along a measured tape or known distance (a 100-foot driveway is convenient) using your normal stride. Count your steps. Divide 100 by your step count to get your step length in feet. For most adults, walking pace is 2.0 to 2.8 feet per step, with most men in the 2.4 to 2.7 range and most women in the 2.1 to 2.4 range. To pace out 209 feet, multiply 209 by your steps-per-100-feet count and divide by 100. For someone with 39 steps per 100 feet (2.56 ft per step), 209 feet equals 82 steps.

Mark your starting point. Walk 209 feet (82 steps in this example) along the property edge, marking the endpoint. Turn 90 degrees and walk another 209 feet, marking the endpoint. Repeat twice more to close the square. The enclosed area is one acre. If your actual property boundary extends well outside this 209-foot square, the parcel is larger than one acre. If your boundary falls well inside, the parcel is smaller. For better resolution, pace out a 0.25-acre square (104 feet on a side, 41 steps in the same example) or a 0.5-acre square (148 feet on a side, 58 steps).

Pacing accuracy depends on consistent stride and accurate 90-degree turns. Most people can pace 200 feet with 5 to 10 percent error in straight-line distance, and turn corners with 5 to 10 degrees of error. Combined, pacing-method area estimates are accurate to roughly 10 to 15 percent. The technique is most useful as a sanity check (confirming whether a quoted parcel size matches the visible area) rather than as a precise measurement.

Method 4

Drone photogrammetry

For high-precision area measurement without licensed-survey costs, consumer-grade drone photogrammetry is the best option. The workflow involves flying a small drone (DJI Mini 4 Pro at $759 retail or DJI Mavic 3 at $2,200 are both popular consumer choices) over the parcel to capture overlapping photographs. The photographs are processed through software (DroneDeploy at $200/month subscription, Pix4D Cloud at $250-500 per project, free OpenDroneMap for technically inclined users) which stitches them into a high-resolution orthomosaic and a digital elevation model.

Without ground control points, drone photogrammetry produces orthomosaics with horizontal accuracy of 1 to 3 metres (matching the GPS accuracy of the drone) and vertical accuracy of 2 to 5 metres. For most planning and visualisation purposes this is excellent. With ground control points (5 to 10 surveyed marks placed on the parcel before the flight, typically using a survey-grade GPS receiver or measured against known reference points), accuracy improves to 5 to 30 cm horizontally, approaching survey-grade.

For a typical 5-acre parcel, a single drone flight at 100 metres altitude collects 200 to 400 overlapping photographs in 15 to 25 minutes of flight time. Cloud processing of the photographs takes 2 to 4 hours. The result is a centimetre-resolution orthomosaic that can be opened in QGIS, ArcGIS, Google Earth, or any other GIS software for area measurement, slope analysis, and feature mapping. Total cost for a one-off project (drone hire if not owned, software processing, and 4 to 8 hours of operator time) typically runs $200 to $500.

Note that recreational drone flight in the US is regulated by the FAA. Drones over 250 grams must be registered with the FAA ($5 fee, valid for 3 years). Commercial drone flight (including paid surveys for property owners) requires a Part 107 Remote Pilot Certificate, which involves a written exam and ongoing recurrent training. Local rules also apply: many state and municipal parks prohibit drone flight, and some counties require permits for any non-recreational drone work. For property-owner self-survey purposes, recreational flight rules apply if the operator is the property owner and is not paid for the work.

Method 5

Licensed boundary survey

For any measurement that will be used in a legal record, a licensed land surveyor is required by every US state. The surveyor will research the recorded deed and any prior surveys, locate the recorded property corners using GPS or total station, identify any encroachments, gaps, or overlaps with neighbouring parcels, and produce a stamped legal survey document and plat that can be recorded with the county.

Boundary surveys come in several types. A boundary survey identifies and marks the property corners and produces a plat showing the boundary lines, dimensions, and any visible improvements. A topographic survey adds ground elevation contours, useful for site planning and drainage analysis. An ALTA/NSPS land title survey (the highest-detail level, named for the American Land Title Association and National Society of Professional Surveyors) is required by most commercial lenders and includes utility locations, easements, and detailed encroachment analysis. A construction stake-out survey marks proposed building corners, foundation lines, and elevation references for builder use.

Typical 2024 to 2025 cost ranges in the US: a basic residential boundary survey on a 0.5 to 1.5 acre parcel runs $400 to $1,200 depending on location and complexity. The same survey on a 5 to 10 acre rural parcel runs $800 to $2,500. Suburban Northeast and California prices are typically 50 to 100 percent above the national average. ALTA/NSPS surveys add $1,500 to $5,000 over a basic boundary survey because of the additional research and detail required. Topographic surveys typically add $500 to $2,000 over a boundary survey for the elevation work.

Survey accuracy is governed by state law, typically requiring positional accuracy of 0.07 feet (about 1 inch) or better for residential surveys, with relative accuracy between adjacent corners of 1 in 5,000 (which on a 1-acre square means corners must be located within about 0.04 feet, or half an inch, of true position). This is roughly 1,000 times more accurate than a Google Maps measurement.

For most homeowners, a licensed survey is needed for: deed transfer at sale (often required by lender or title insurer), boundary disputes with a neighbour, building permit applications for new construction or major additions, partition or subdivision of a parcel, and fence or driveway installations near the property line. Outside these contexts, a free or low-cost method is usually sufficient.

Frequently asked, measurement edition

Related pages

• · How big is an acre? Chain-and-furlong derivation
• · Visual reference, all acreages
• · Survey foot vs international foot
• · Glossary: chain, plat, easement, monument