Buildable Envelope Calculator

Planning calculator

A tool for estimating a simple rectangular buildable envelope using lot dimensions, setbacks, and lot coverage.

How it works

The tool calculates buildable width, buildable depth, envelope area, lot area, maximum footprint by lot coverage, and the estimated maximum building footprint. The estimated maximum building footprint is the lower of the setback-based envelope area and the lot coverage limit.

When to use it

  • Best used for early planning checks, zoning screening, site layout review, and comparing how setbacks and lot coverage affect building potential.
  • Not used for confirming final buildable area on irregular lots, constrained sites, or sites affected by easements, environmental buffers, floodplain requirements, access needs, servicing constraints, topography, or survey issues.
  • Audience: Planners, applicants, designers, consultants, and property owners doing preliminary site planning.

Notes and limits

  • Assumption: The tool assumes a rectangular lot and applies front, rear, and side setbacks as simple rectangular deductions.
  • Known constraint: The tool does not account for zoning exceptions, projections, averaging, easements, riparian areas, statutory rights of way, title restrictions, environmental buffers, floodplain requirements, servicing constraints, topography, or survey accuracy.
  • Edge case: Where the lot is irregular, angled, panhandled, or affected by site-specific constraints, the real buildable area may be smaller than the calculated envelope.

Disclaimer

This tool is for general information only. It may contain errors or omissions. Use at your own discretion. No liability is accepted for decisions made based on this tool.

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