Density Bonus Tradeoff Calculator

Density bonus math: more units, set-aside burden.

Base units

Bonus % awarded

Affordable set-aside %

Market rent per unit/yr

Affordable rent per unit/yr

Cap rate %

Net value of bonus decision

$12,436,364

Bonus unit gross value

$16,363,636

Set-aside cost

$3,927,273

How the math works

Bonus units = base × bonus %. Affordable = total × affordable %. Bonus value = bonus × rent / cap. Cost = affordable × gap / cap.

30 bonus units × $30k / 5.5% = $16.4M value. 18 affordable × $12k gap / 5.5% = $3.9M cost. Net $12.5M — density bonus strongly accretive.

How to Use

Enter base units.
Enter bonus % awarded.
Enter affordable set-aside % required.
Enter market rent per unit.
Enter affordable rent per unit.
Enter cap rate.
Read net value of bonus decision.

Frequently Asked Questions

Typical tradeoffs?

California State Density Bonus: 20% bonus units for 5% very-low affordable. Net: almost always positive (bonus units more value than affordable rent gap). But depends on market rents, site constraints, construction costs per unit. Math on case-by-case basis.

When not to take?

Expensive construction types where bonus unit cost exceeds affordable rent gap discount. Sites where bonus units don't fit physically. Complex compliance burden. Alternative paths to density (rezone, PUD). Some markets: alternative fee-in-lieu cheaper.

Model carefully?

Run three scenarios: (1) base no bonus, (2) bonus with required set-aside, (3) alternative path. Include: construction cost per bonus unit, rent premium, affordable rent gap, compliance monitoring cost, value at exit. Best scenario varies by market.