Lot Size Calculator
Trace a lot or parcel on the map to measure geodesic area — ideal for real estate, gardens and land checks.
By Aryan Khan, Founder & Editor · Updated October 2026
For example, a 100 × 150 ft lot is 15,000 square feet — 0.344 acres — while doubling both sides to 200 × 300 ft quadruples it to 1.377 acres, not doubles.
How to use Lot Size Calculator
Length × width, then the units fan out:
The Lot Size Calculator multiplies a rectangular lot's length and width into its area, reported in square feet, acres, hectares and square metres. Enter the two dimensions and read the size in every unit a listing or deed might use — the arithmetic behind 'quarter-acre lot'.
- 1Click the map to place each corner of the lot.
- 2Close the shape when the outline is complete.
- 3Read area and perimeter in the units you need.
What people use Lot Size Calculator for
1. Verifying listing claims
‘Quarter-acre lot’ with 60 × 150 ft dimensions? That is 9,000 sq ft — 0.207 acre, and the claim is generous. The calculator is the lie detector; the missing-side solvers (Lot Depth From Area and Width) help when a dimension is coy.
2. Comparing lots across unit systems
A European 800 m² plot and an American 8,600 sq ft lot are near-twins (800 m² ≈ 8,611 sq ft). One calculator, both dialects, no conversion errors.
3. Feeding downstream calculations
Per-acre pricing, seed, mulch, mowing and fencing all begin with area. This is the number they consume — get it here once, correctly.
4. Estate and garden planning
A 200 × 300 ft homesite at 1.377 acres plans very differently from its 0.344-acre suburban cousin — buildings, septic, orchard and ego all scale with the area.
Worked examples
One acre as a square has sides of 208.7 ft — a useful mental picture: an American football field is 1.32 acres including end zones, and a square acre is a bit under three-quarters of the field's footprint.
100 × 150 ft = 0.344 acre; 200 × 300 ft = 1.377 acres. Area grows with the square of dimension — the most underestimated multiplication in property browsing.
Common lot sizes
Dimensions to area, in the units listings mix.
| Dimensions | Square feet | Acres |
|---|---|---|
| 50 × 100 ft | 5,000 | 0.115 |
| 66 × 165 ft | 10,890 | 0.250 |
| 100 × 150 ft | 15,000 | 0.344 |
| 150 × 200 ft | 30,000 | 0.689 |
| 200 × 300 ft | 60,000 | 1.377 |
| 208.7 × 208.7 ft | 43,560 | 1.000 |
Rectangular math. Irregular lots — most rural parcels and many urban ones — need the drawn-polygon measurement of the Map Area 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.
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.
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.
Editorial guidance: MapBench explains the method and limitations so the tool can be used as a transparent reference, not as a black-box answer. For legal boundaries, safety-critical routing, surveying, engineering, regulated decisions or official statistics, verify the result with the responsible authority or a qualified professional.
Category: Radius & Area. Results are intended for everyday analysis and planning unless a page explicitly states otherwise.
Method, assumptions & limits
- This tool’s method
- Geodesic polygon area on the WGS84 ellipsoid from the vertices you draw.
- Before relying on the answer
- Check the centre, radius or drawn vertices and the selected units. A geometric footprint does not describe which roads or entrances are accessible.
- What the result cannot establish
- A radius is not a travel-time guarantee. For parcel boundaries or legal land area, use an authoritative survey.
Coverage: Worldwide. Search, basemap and external data requests may use third-party services; browser-based does not mean every operation is offline. Read the source and licence notes, calculation methodology and privacy policy. If a result looks inconsistent, report a correction with the inputs and mode used.
Frequently asked questions
Clear answers about the calculation, accuracy and appropriate use.
Survey accurate?
No — this is a planning estimate from the map. Legal boundaries need a licensed surveyor or official plat.
Units?
Area is shown in m², km², acres, hectares and related units.
Is a radius the same as driving distance?
No. A radius is a geometric circle around a centre point. Driving reach depends on the road network and usually has an irregular shape.
Can I use this for service-area planning?
Yes for first-pass planning. Use a drive-time or road-network tool when accessibility matters more than straight-line coverage.
Are map measurements legal survey measurements?
No. MapBench measurements are planning/reference outputs unless a page explicitly states otherwise. Use a licensed surveyor for legal boundaries.
What if my lot is a triangle or trapezoid?
Triangles take base × height ÷ 2, trapezoids average the parallel sides — but the honest general tool is drawing the parcel in the Map Area Calculator, which prices any shape geodesically.
Are easements and road frontage included?
Deed area usually includes land under easements and sometimes to the road's centreline. The calculator computes the dimensions you give it; what the law counts is a title question.
Metres from a European deed?
Enter metres and read every unit — 20 × 40 m is 800 m², 0.198 acre. No pre-conversion needed.
Why doesn't my survey match the listing?
Listings round, borrow from tax records, or err. The survey is the legal instrument; the calculator's role is exposing the gap in thirty seconds.
Usable versus total area?
Slope, wetlands, floodplain and setbacks shrink usable land below deed area. This page gives the deed number; the buildable number needs the local rules applied to it.
How many houses fit?
Zoning sets minimum lot sizes and densities — divide your area by the zone's minimum and you have the theoretical count, before roads and reality take their share.
Precision of the answer?
Exact for the inputs. Tape-measure inputs give tape-measure truth: a 1% error in each side is a 2% error in area, which on an acre is 871 sq ft of fiction.
Related tools and resources
Drawn shapes: the Map Area Calculator; missing sides: Lot Depth From Area and Width and Lot Width From Area and Depth; price it: the Land Cost Per Acre Calculator.
More free tools
Sources, methodology & editorial trust
- ✓ Browser-first processing where supported
- ✓ External sources are documented
- ✓ No account required for public tools
- ✓ Review data sources
Calculations are documented with their assumptions, limitations and source context rather than presented as unexplained answers.
Reviewed and maintained by Aryan Khan, Founder & Editor of MapBench.
Part of our area & acreage hub
Lot Size Calculator sits in the area & acreage cluster, alongside 26 other tools that answer neighbouring questions with different methods or datasets.
You may also need
When this answer is only part of the job, these clusters cover the next step.
Read the guide behind this tool
How to Measure Land Area on a Map: Acres, Hectares and Square Feet — Learn how map-based area measurement works, how to trace a parcel more accurately, how acres and hectares relate, and when an online estimate is not enough.