Lot Size Calculator

Estimate lot size from a visible boundary, then verify legal acreage separately

This tool is designed for people who want a quick estimate of a lot or parcel-sized area from a map. Draw the boundary and convert the result into acres, hectares, square feet or other practical units. It is especially useful for comparing listings, planning landscaping, checking rough development scale or understanding how a stated acreage looks on the ground.

A map trace is not a substitute for a recorded deed, cadastral polygon or licensed survey. Fences, driveways and imagery edges may not coincide with legal ownership. If a property decision depends on a small difference in area, use the official parcel record rather than increasing map zoom and assuming that creates survey-grade accuracy.

When this tool is useful

Use Lot Size Calculator when the question matches the method the page actually uses. Typical workflows include:

• Use the output as a planning or teaching reference, then move to an official or specialist source if the result affects legal, safety, engineering or financial decisions.
• Run the same workflow for locations in different countries while keeping units and assumptions consistent.
• Answer a one-off question about lot size calculator and keep the result tied to a visible map or explicit input.

Worked examples

These examples are meant to show how to interpret this kind of output, not to replace the values produced from your own inputs.

• 5-mile radius — A 5-mile circle encloses roughly 203 km². This is geometric coverage, not a promise about driving time or service accessibility.
• 10-mile radius — A 10-mile circle encloses roughly 814 km². This is geometric coverage, not a promise about driving time or service accessibility.
• 25-mile radius — A 25-mile circle encloses roughly 5,085 km². This is geometric coverage, not a promise about driving time or service accessibility.

How to interpret the result

The most common errors come from using a correct result to answer the wrong geographic question. Keep these points in mind for Lot Size Calculator:

• When exporting polygons for reports, store the radius and unit in the feature properties (the exports here do). Future-you, reopening the file in a GIS, will otherwise have to re-derive what the circle meant.
• Decide geometric vs temporal reach before drawing anything: a 10 km circle and a 15-minute drive area answer different questions, and in car-dependent geography they barely overlap in shape. Circles for policy radii, isochrones for response promises.

Limits & appropriate use

Circles and polygons are geometric truths with semantic limits. A radius says nothing about rivers, one-way systems or response times; an area says nothing about what is inside it. The most expensive misuse is treating a geometric catchment as a service promise — which is why the isochrone tools exist as the temporal counterpart, and why the pages cross-link the two insistently. A second limit is resolution: drawn vertices capture the boundary you click, so curved shores want more clicks, and the perimeter grows (correctly) as you add them — the coastline paradox, politely present in every honest measurement tool.

Within geometry, the numbers are exact on the sphere: areas by spherical excess, boundaries by destination math, exports with their parameters embedded. The escalation ladder is short: cadastral precision needs licensed surveys; population-inside-shapes needs census blocks; drive-time promises need the routing engine. Used as the fast, auditable, shareable geometric layer that feeds those heavier instruments, this is exactly the right tool — and it says so.

• Cadastral/legal area → licensed survey with local datum practice.
• Population inside shapes → census blocks, not city-point sums.
• Response-time promises → isochrones plus operational buffers.

Data & methodology

Geodesic polygon area on the WGS84 ellipsoid from the vertices you draw. Circle boundaries are placed vertex-by-vertex by spherical destination math; polygon areas use spherical excess on the WGS84 sphere — both remain correct at high latitudes where flat formulas fail.

For source details, licences and model limitations, see Data Sources and Methodology.

Key terms worth knowing

Catchment

The area or population served from a centre, geometric or temporal.

Perimeter

The summed great-circle length of a drawn boundary.

Go deeper: guides & original studies

Use these resources when you need the reasoning behind the calculation, a comparison with another geographic method, or an example of the same approach applied across a dataset.

Related tools

If this page answers only part of your question, these tools use a nearby but different method or dataset.