Affordable Housing Requirement Calculator
Calculate inclusionary housing units required for a development, affordable rent limits, density bonuses, and fee-in-lieu costs.
About this calculator
This calculator models inclusionary zoning requirements — the affordable units a developer must set aside as a condition of building market-rate housing. Required Affordable Units is Total Proposed Units multiplied by the Inclusionary Rate, rounded up to the next whole unit, since a fractional unit isn't buildable and jurisdictions generally round in the affordable direction. Density Bonus adds extra buildable units on top of the base project as an incentive for providing affordable housing, so Total Units (with bonus) can exceed Total Proposed Units, and Market-Rate Units is whatever remains after subtracting Required Affordable Units from that bonused total. Max Affordable Rent applies the standard HUD affordability threshold — housing costs at or below 30% of income, the same line HUD and the Census Bureau use to define a household as "cost-burdened" once spending crosses it — to an income set at your chosen AMI Target Level (a fraction of Area Median Income), then subtracts a flat $150/month utility allowance to estimate rent alone rather than total housing cost.
Both AMI Target Level and Area Median Income multiply directly into that income base, so either one moving changes Max Affordable Rent — AMI Target Level's six fixed tiers (30% Extremely Low to 120% Workforce) tend to swing Max Affordable Rent more than a typical adjustment to Area Median Income, since choosing a different tier can multiply the income base by up to 4x in one step, while Area Median Income for a given jurisdiction changes more incrementally. Annual Revenue Gap and Total Revenue Gap estimate the developer's opportunity cost — the market rent an affordable unit could have commanded versus the capped affordable rent it must charge instead — projected across the number of required units and the Affordability Period the deed restriction stays in effect. Three Bed is one quarter of a bedroom-mix breakdown applied to Required Affordable Units, using a typical distribution of 15% studio, 35% one-bedroom, 35% two-bedroom, and the remainder three-bedroom or larger — a planning assumption for unit-type mix, not a zoning requirement.
Inputs
Results
Required Affordable Units
15
Max Affordable Rent
$1,350.00
Figures current as of 2026. Source: U.S. Department of Housing and Urban Development affordability standard, as reported in U.S. Census Bureau housing-cost-burden data
How to Use This Calculator
- Enter Total Proposed Units, Inclusionary Rate, and Area Median Income for the jurisdiction.
- Select an AMI Target Level (30% Extremely Low up to 120% Workforce) and set the Affordability Period.
- Optionally add a Density Bonus, and choose Build On-Site Units or Pay Fee In Lieu (with Fee In Lieu per Unit if paying).
- Review Required Affordable Units and Max Affordable Rent (/mo).
- Use Market-Rate Units, Total Units (with bonus), and Annual Revenue Gap to inform your decision.
How the result changes with Total Proposed Units
| Total Proposed Units | Required Affordable Units | Max Affordable Rent |
|---|---|---|
| 50 | 8 | $1,350.00 |
| 75 | 12 | $1,350.00 |
| 150 | 23 | $1,350.00 |
| 250 | 38 | $1,350.00 |
What each input means
- Total Proposed Units
- Total number of residential units in the proposed development.
- Inclusionary Rate
- Required percentage of units set aside as affordable. Typical range is 10-20%.
- AMI Target Level
- Target Area Median Income level for affordable units. Lower AMI = more affordable.
- Area Median Income
- HUD Area Median Income for the jurisdiction (household of 4).
- Affordability Period
- Duration the affordable units must remain income-restricted.
- Density Bonus
- Additional units allowed as incentive for providing affordable housing (varies by jurisdiction).
- Compliance Method
- Whether the developer will build affordable units or pay a fee to an affordable housing fund.
- Fee In Lieu per Unit
- Fee per required affordable unit if paying in lieu of construction.
What each result means
- Three Bed
- Three-bedroom share of Required Affordable Units, using a typical bedroom-mix assumption of 15% studio / 35% one-bedroom / 35% two-bedroom / 15% three-bedroom (three-bedroom is the remainder after rounding the other three).
How this is calculated
Worked example, using the default values
- Identify Input Parameters8 parametersTotal Proposed Units = 100, Inclusionary Rate = 15, AMI Target Level = 80, Area Median Income = 75000, Affordability Period = 30, Density Bonus = 0, Compliance Method = 0, Fee In Lieu per Unit = 50000 = 8 input(s) provided
- Calculate Required Affordable UnitsRequired Affordable Units15 = 15
- Calculate Max Affordable RentMax Affordable Rent1350 = $1,350
- Calculate Market-Rate UnitsMarket-Rate Units = max(085 = 85
- Calculate Total UnitsTotal Units100 = 100
Figures and sources
- Housing cost-burden threshold (30% of income) (2026) — U.S. Department of Housing and Urban Development affordability standard, as reported in U.S. Census Bureau housing-cost-burden data
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Do AMI Target Level and Area Median Income affect Max Affordable Rent equally?
Both multiply directly into the income base Max Affordable Rent is calculated from, so either one changes the result, but AMI Target Level tends to move it more. Switching between its six fixed tiers (30% Extremely Low up to 120% Workforce) can multiply the income base by up to 4x in a single step, while Area Median Income for a real jurisdiction typically changes more incrementally within its declared range.
Why does Max Affordable Rent use 30% of income specifically?
That 30% figure is HUD's own standard threshold for housing affordability — the U.S. Department of Housing and Urban Development, and the Census Bureau data that tracks housing costs nationally, both define a household as "cost-burdened" once its housing spending crosses 30% of income. This calculator applies that same threshold to derive Max Monthly Housing Cost from your chosen AMI Target Level and Area Median Income, then subtracts a flat utility allowance to land on Max Affordable Rent.
Why doesn't Area Median Income affect Required Affordable Units?
Required Affordable Units is calculated purely from Total Proposed Units and Inclusionary Rate — the count of units required is a zoning-code percentage of the project's total unit count, unrelated to what those units actually rent for. Area Median Income only enters the affordability calculations (Max Affordable Rent, Target Income, and the revenue-gap figures), never the count of required units itself.
Does Fee In Lieu per Unit change how many affordable units are required?
No — Required Affordable Units is fixed by Total Proposed Units and Inclusionary Rate regardless of the Compliance Method you select. Fee In Lieu per Unit only determines Total Fee In Lieu, the dollar amount owed if you choose "Pay Fee In Lieu" instead of building the required units on-site; it has no effect on how many units the inclusionary requirement calls for.
Why does a longer Affordability Period increase Total Revenue Gap but not Required Affordable Units?
Total Revenue Gap multiplies Annual Revenue Gap by Affordability Period, projecting the developer's opportunity cost over however many years the units stay deed-restricted — a longer period simply accumulates more years of the same annual gap. Required Affordable Units is a one-time unit count set by zoning code at approval, unrelated to how long the restriction subsequently lasts.
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