Implementation math: FAR, density, parking, and more

Learning objectives

• Convert between square feet, acres, and square miles without hesitation.
• Calculate floor area ratio, building height from FAR and coverage, lot coverage, and the largest building when several limits apply at once.
• Calculate gross and net density, units allowed under a minimum-lot-area rule or density bonus, the density needed to fit projected growth, and the land a cluster subdivision leaves open.
• Calculate required parking (including mixed uses) and the land area it consumes, and peak-hour trip generation.
• Calculate housing cost burden, affordable monthly housing cost, and income as a percentage of area median income.
• Calculate the slope of a site as a percentage and read what it means for development.

Key concepts

The AICP exam includes a handful of calculation questions. None needs advanced math, but they reward planners who set up the problem carefully. Each section below gives the formula, then a worked example. Try each example yourself before reading the answer.

Units you must know

• 1 acre = 43,560 square feet
• 1 square mile = 640 acres
• A percentage is a fraction of 100: 30% = 0.30.

12 more sections follow in the full lesson.