Measure your yard from above

How we work it out

The photo is Esri's World Imagery, which stitches together recent aerial and satellite photos, sharp to about a foot on the ground in most US towns.

Lengths are measured along the curve of the Earth between the points you click, and areas on a flat projection centered on your shape. At yard scale the math is far more exact than the photo, so the photo is the limit: expect lengths within a foot or two and areas within about 5% when the edges are clear.

Trace where things meet the ground. Roofs lean in aerial photos and trees hide edges, so a house traced by its roofline comes out shifted. The address search goes to the US Census Bureau's public geocoder, which estimates a spot along the street. Where a public address-point list covers the address (the federal National Address Database, or SanGIS in San Diego County), the pin moves onto the lot. Nothing is stored. Your drawing lives only in this page's link and your browser.

The 3D view draws the 260 ft square around the map's centre from USGS 3D Elevation Program lidar: laser points measured from a plane, usually two or more on every square metre. Your browser downloads them from the USGS public store and sorts them into ground, roofs and trees, with the same method we checked against houses we know the heights of. Tap any point for its height above the ground. Each survey is from one year, so newer buildings and grown trees won't show.

In Arkansas, Connecticut, Hawaii, Maryland, Massachusetts, New Jersey, North Carolina, Utah, Vermont, Virginia and Washington, DC, in most of Colorado, and in King County (WA), the Portland and Twin Cities metros, Indianapolis, Oakland County (MI), Rochester (NY), Milwaukee, San Francisco, Sacramento and San Diego counties (CA), San Antonio (Bexar County, TX), Baton Rouge, Ada County (ID), Fulton and DeKalb counties and Johns Creek (GA), Sioux Falls (SD) and Fargo (Cass County, ND), a Property lines button draws the parcel lines over the photo. They come straight from each government's public map service, under terms that allow reuse, and they're approximate: good for finding roughly where your lot ends, not for setting a fence. A survey settles that.

Flood zones. Wherever FEMA has a digital flood map, the Flood zones button lays FEMA's flood map over the photo, in FEMA's own colours, and says in words which zone sits under the crosshair: a special flood hazard area (the 1% annual chance floodplain, zones A and V), a moderate hazard (the 0.2% chance floodplain) or minimal hazard, with the base flood elevation where the map sets one and the FIRM panel it comes from. Those are the zones federal rules (44 CFR 64.3) say mandatory flood insurance applies to. It reads FEMA's National Flood Hazard Layer, so it's a planning look, not a flood determination: the official map is on FEMA's Flood Map Service Center, and a lender orders its own.

Set something down. Sheds, hot tubs, patio sets, grills, fire pits, playsets' safe play areas and cars drop onto the photo at their makers' sizes, the same ones our guides use. Drag and turn them. Grills and fire tables draw their makers' clearance as a dashed line; a wood fire pit checks the fire code's 25 ft against the areas you've drawn. With property lines on, each one shows its distance to the lot line, and against your town's setback if you put it in.

An ADU on your lot. San Diego County's six free ADU plans set down at their outside size, L-shapes included. Placing one turns the property lines on, and a dashed ring 4 ft out, California's cap on an ADU's side and rear setbacks, goes amber when a lot line comes inside it. Its tag gives the distance to the lot line as you drag, and Line up with the lot turns it square to the nearest line. Open the 3D view and it stands beside your house at its real height, with the state's 16 ft limit dashed above it. See the ADU floor plans for the blueprints.

Historic places. The Historic places button checks the National Park Service's National Register at the crosshair: the districts and properties whose boundary takes it in, and listed buildings within about 60 m, with the year each was listed and its nomination form. Some boundaries are only an approximate box, and the card says so. A National Register listing alone places no federal limits on a private owner; local historic districts usually do, and they aren't in this map.

Split the lot (California SB 9). Click across your lot, on its property line or an outline you trace, and it shows both new lots with their areas. In California it checks them against SB 9's urban lot split (Government Code § 66411.7): each at least 1,200 sq ft, neither under 40% of the original. It checks FEMA's flood map at each one, since SB 9 leaves out special flood hazard areas unless they meet FEMA's rules. Split it evenly moves the line to 50/50. It lists what a map can't check, from the zoning to the 3-year owner-occupancy affidavit.

Ground slope. On any line you draw, Get the ground slope asks USGS's Elevation Point Query Service for the bare-ground height every 5 ft or so (up to 20 points), from the 3D Elevation Program. That's 1 m data where there's lidar and about 10 m elsewhere; the result says which. USGS elevation data is free and public domain.