Inclusionary Zoning Value Calculator

Inclusionary zoning trades affordable set-aside for density bonus.

Base units

IZ bonus units

Affordable set-aside %

Market rent / mo

Affordable rent / mo

IZ net annual value

$420,000

Bonus unit value

$750,000

Set-aside cost

$330,000

How the math works

Bonus value = bonus units × market × 12. Set-aside cost = affordable units × rent gap × 12.

25 × $2,500 × 12 = $750k bonus. 125 × 20% × $1,100 × 12 = $330k set-aside cost. $420k IZ net value.

How to Use

Enter base units allowed.
Enter IZ bonus units.
Enter affordable set-aside %.
Enter market rent / mo.
Enter affordable rent / mo.
Read IZ economic value.

Frequently Asked Questions

What is inclusionary zoning?

Zoning requirement or incentive that developers include affordable units in market-rate projects. Mandatory IZ: required (common in SF, NYC, Boston). Voluntary IZ: incentive via density bonus. Typical set-aside: 10-25% of units affordable. Typical bonus: 15-35% additional units. Net economics depend on specific program. Some IZ programs penalize development; others generate positive value.

How is value calculated?

Value = (bonus units × market rent) − (affordable set-aside × (market − affordable rent gap)). If bonus market value exceeds affordable rent discount, IZ creates net value. In strong markets, bonus wins. In weak markets, set-aside hurt exceeds. Example: 100 base units + 25 bonus + 10 affordable. Market $2,500, affordable $1,500. Value = 25 × $30k − 10 × $12k = $750k − $120k = $630k positive.

Program variations?

Fixed bonus (fixed density add regardless of set-aside %). Variable bonus (larger set-aside = larger bonus). In-lieu fee (pay instead of building affordable — often punitive). Off-site affordable (build affordable elsewhere in same municipality). Income tier flexibility (80% vs 50% vs 30% AMI). Each jurisdiction different — no one-size analysis.

When does IZ not work?

(1) Rent gap too large (luxury market, deep affordable). Bonus doesn't compensate. (2) Set-aside too aggressive (>25%). (3) Construction cost inflation + labor (cost up but affordable rent limits hold). (4) Weak market (bonus units not renting). (5) Complex compliance. Some markets (LA, Seattle) see developers opt for in-lieu fee or walk away from IZ-triggered projects. Case-by-case analysis essential.