Planning calculator

Square Footage Calculator

Combine rectangular, triangular, and circular sections into one project area. Switch between US customary and metric units, adjust the assumptions, and keep every step visible.

01 Measure02 Allow03 Order

Project inputs

Use one unit system throughout. Defaults show a realistic example; replace them with measurements from your project.

Unit system

Rectangle lengthExample input — replace with your project value.ftRectangle widthExample input — replace with your project value.ftTriangle basePlanning default — verify the selected product or project specification.ftTriangle heightPlanning default — verify the selected product or project specification.ftCircular section diameterPlanning default — verify the selected product or project specification.ft

Measurement guideMeasure each rectangular section, then add any extra measured area.

Measure the finished shape. Split irregular plans into rectangles, triangles, and circles, then enter zero for any unused section.

Estimate matches the inputs shown.

ReviewedNovember 2, 2026

ByBuildGauge Editorial Team

ScopeFormula, defaults & sources

Report an issue ↗

The calculation

A visible formula, not a black box.

Area · Mathematical derivationtotal area = length × width + triangle base × height ÷ 2 + π × (diameter ÷ 2)²

Inputs are converted to a common base unit before calculation. Purchase quantities are rounded only at the final buying boundary.

Example inputDefaultStatus

Rectangle length12 ftReplace with measurement

Rectangle width10 ftReplace with measurement

Triangle base6 ftPlanning default — verify

Triangle height4 ftPlanning default — verify

Circular section diameter3 ftPlanning default — verify

Worked example

Example: planning square footage

Using the editable example inputs—rectangle length 12 ft, rectangle width 10 ft, triangle base 6 ft—the calculator returns 139.1 ft². Replace every example with measured dimensions and the selected product label before purchase.

Use this to understand the workflow—not as a recommendation for your project.

Sources & scope

What supports this calculation.

Industry guidanceStandard plane geometry ↗

Supports the product rule or estimating basis used by the Square Footage Calculator; geometry and unit conversion remain visibly derived in the calculator.

Mathematical derivationNIST SI conversion factors ↗

Exact length, area, and volume unit conversions; the project formula is derived from standard geometry.

Common mistakes

Check the job, not just the number.

01Leaving the example square footage inputs unchanged instead of entering measured project values.
02Treating an editable coverage, size, density, or allowance as universal instead of checking the selected product label, project documents, and local requirements.
03Ordering from the rounded result without reviewing exclusions: Split irregular plans into rectangles, triangles, and circles, then enter zero for any unused section.

Questions, answered

Square footage FAQ

What does the Square Footage Calculator estimate?

Combine rectangular, triangular, and circular sections into one project area. The primary output is area, with the intermediate assumptions kept visible.

How is the square footage result calculated?

The visible formula is: total area = length × width + triangle base × height ÷ 2 + π × (diameter ÷ 2)². Inputs are converted to a common base unit before the final purchase boundary is rounded.

Are the default values recommendations?

No. Dimensions are worked examples and product-dependent presets are planning defaults. Replace them with the selected product label, project documents, and local requirements.

Is the result ready to order from?

Use it as a checked planning estimate, then confirm packaging, minimum orders, installation instructions, site conditions, and any code or professional-design requirements.