How to Measure Land Area by Satellite or GPS on Your Phone

Published October 30, 2026

To measure land area from your phone, open a measuring app with a satellite map, tap each corner of the plot on the imagery, and the app instantly calculates the area (in acres, hectares or square feet) and the perimeter. If the boundary is hard to see from above, walk it instead with your phone's GPS turned on.

It works the same way for a backyard, a building lot, a pasture or a 200-acre farm, and it takes a few minutes. This guide covers both methods, when to use each, and the conversions people ask about most, including how many acres are in a square mile.

How to measure area on a map, step by step

We'll use Field Maps with Area Measure as the example. It's an iPhone and iPad app (iOS 17 or later) that measures two ways: tapping points on a satellite map, or walking the boundary with GPS.

Method 1: tap points on the satellite map

1. Find the property. Center the map on your location or pan to the land, then zoom in until you can see fences, walls, tree lines, tracks or field edges.
2. Choose area measurement and tap the first corner.
3. Work around the boundary in order, tapping each corner or change in direction. Along curved edges, such as a creek or a winding lane, add extra points.
4. Close the shape. Area and perimeter update live as you draw, and you can drag any point that isn't sitting exactly on the line.
5. Save the measurement with a name you'll recognize ("North pasture", "Lot 7") so you can come back to it or share it.

Only need a length, like a fence run or a frontage? Use distance mode instead of area mode.

Method 2: GPS field mapping on foot

1. Stand at one corner and give your phone's GPS a few seconds under open sky to settle.
2. Start a GPS measurement from that point.
3. Walk the boundary at a steady pace, always on the same side of the fence.
4. Return to the start and close the track to get the area and perimeter of what you walked.
5. Check the outline against the satellite image and fix any points that drifted before saving.

GPS mapping works offline in the field, which matters on rural land with no signal.

Satellite tapping vs GPS walking: which gives better field map measurements?

Tapping on satellite imagery is usually the more precise option for small and medium plots, because you decide exactly where each corner goes. It also lets you measure remotely, from your desk, as long as the boundary is visible in the image.

Walking with GPS is the better choice when edges aren't visible from above (uniform grass, scrub, survey pins hidden in brush) or when the imagery is out of date. A phone's GPS is typically accurate to within about 3–5 m (10–16 ft) under open sky, and it gets worse under trees, next to buildings or in steep valleys.

That margin matters more the smaller the plot. On a 50 × 100 ft lot (5,000 ft²), reading it as 53 × 103 ft gives 5,459 ft², about 9% too much. On a farm field of many acres, the same few feet barely register. So for a yard or a building lot, satellite tapping is usually the way to go; for a large field with fuzzy edges, GPS surface mapping on foot is very practical.

Measuring land perimeter

Perimeter is shown alongside area, and it's the number you need for fencing, edging or a hedge. If you only care about the map perimeter of a property, trace the outline the same way and read the perimeter off the result.

How many acres in a square mile?

There are 640 acres in one square mile. A square mile is a square one mile (5,280 ft) on each side, which is 27,878,400 ft². Divide that by 43,560 ft² per acre and you get exactly 640.

On a map, that's easy to picture in much of the US: a standard survey "section" is nominally one square mile, or 640 acres, and a quarter section is 160 acres. In metric terms, one square mile is about 259 hectares, or 2.59 km².

Other conversions worth keeping handy:

• 1 acre = 43,560 ft² = 4,840 yd² = 4,046.86 m² ≈ 0.405 ha
• 1 hectare = 10,000 m² (a 100 × 100 m square) ≈ 2.47 acres
• 1 km² = 100 ha ≈ 247 acres
• 1 square mile = 640 acres ≈ 259 ha ≈ 2.59 km²

A quick way to picture an acre: a square about 208.7 ft on each side. Field Maps with Area Measure shows results in m², ha, km², ft², yd², acres and mi², so you can switch units instead of converting by hand.

Tips for accurate maps area measurements

• Zoom all the way in before placing each point, and put it on the actual corner, not on the shadow of a tree or wall.
• Use more points on curves. A curved edge drawn with too few points cuts off or adds area.
• Be wary of old imagery. If the land has changed (new buildings, a moved fence), confirm by walking it with GPS.
• When walking, go slowly and stay on the same side of the boundary, away from tall walls and under as much open sky as possible.
• Mind the slope. The math is geodesic on the WGS-84 ellipsoid and gives area as a horizontal projection, the way maps normally express it. On steep or terraced ground, the actual ground surface is somewhat larger.
• Compare with your deed or plat. Small differences are normal; large ones are worth looking into.
• Save and share. The free version lets you measure, save, export to CSV or text, create a map image and share a web link. GIS and CAD formats (Shapefile, DXF, KML, KMZ, GeoJSON, GPX), PDF reports, splitting a field into sections, and team workspaces with backup are part of the Pro subscription.

You can see the full feature list on the Field Maps with Area Measure home page.

FAQ

Can I measure land area on my phone for free?

Yes. Measuring area, perimeter and distance, saving measurements, and exporting to CSV or text are free. The Pro subscription adds professional export formats, PDF reports and team features.

How accurate is phone GPS for field mapping?

Under open sky, phone GPS is typically within about 3–5 m. Accuracy drops under tree cover and near buildings. For small plots, tapping points on the satellite map is usually more precise.

Is there an Android version?

Not yet. The app is currently available for iPhone and iPad.

Can I use these measurements for legal boundaries?

No. They're estimates, great for planning planting, pricing a fence or sizing up a purchase. For legal boundaries, property disputes, subdivisions or anything that goes on record, hire a licensed surveyor.