How It Works

The Law

ADU Calculator

Do I Qualify?

FAQs

Calculate Your ADU Cost & Rental Income

Second Unit Basics

{{cityName.city}}
{{type.name}}
New construction includes both attached
and detached second units.

Conversion of part of house means
taking existing living space, e.g. a
basement or part of the house, and
turning it into a second unit.

Modular/panelized are built partially
or entirely off site and delivered
to the property.?
{{bedroom.type}}
If you change the number of bedrooms,
be sure to adjust the square footage accordingly?
{{bathroom.type}}
{{type.name}}
{{type.name}}
{{type.name}}
{{kitchen.type}}
Required message
{{myForm.ADUSqft.$viewValue}} is below 150 sqft minimum
{{myForm.ADUSqft.$viewValue}} is above maximum sqft of {{ADUSqftMax}} in {{cityName}}
sqft
Unit sizes vary significantly,
but typical square footage is:
Studio : 400 sqft

1 Bedroom : 600 sqft
2 Bedroom : 800 sqft
3 Bedroom : 1,200 sqft?
{{finish.type}}
Different levels of interior quality
(e.g. countertops, flooring, etc.) affect
the final construction price. Please choose
the interior quality that best matches your
planned construction.

Low cost: Rental quality. Entry level
appliances, low cost carpet, etc.

Standard: Typical for San Mateo County,
which means generally high quality. Stainless
steel appliances, solid countertops, a mix of
carpet and hardwood or tile.

High cost: Assumes the top end of anything
generally available at major retailers, ceramic
tile floors, etc. Costs would be higher if, for
example, you used a custom cabinet maker.?
{{type.name}}
Required message
{{myForm.ConstructionCost.$viewValue}} is below $50,000 minimum
{{myForm.ConstructionCost.$viewValue}} is above $700,000 max
{{difficulty.type}}
Individual site conditions can significantly
affect construction cost. The most common
reason construction is more expensive is
building on a hillside, but there are
many other potential challenges.?

Rent and Financing

{{type.name}}
Required message
{{myForm.LoanTerm.$viewValue}} is below 1 year minimum
{{myForm.LoanTerm.$viewValue}} is above 30 year max
years
Typical loans are 20 years or less.?
Required message
{{myForm.LoanInterestRate.$viewValue}} is above 7% max
%
Check with your local bank for today's rates?
Required message
${{myForm.CashInvestment.$viewValue}} exceeds the ${{CashInvestmentMax}} construction costs
{{type.name}}
Consider pricing your unit so a teacher or
nurse can afford it. You'll be helping the
community and they make great tenants!?
Required message
{{myForm.Rent.$viewValue}} is below $700 minimum
{{myForm.Rent.$viewValue}} is above $7,115 max
{{type.name}}
Managing a second unit means finding a
tenant and doing repairs as necessary.
Typical costs to hire someone for
this are 5% of the rent.?
{{type.name}}
There have not been enough second units
built to accurately estimate how much
it is likely to increase the value of
a house. The calculator assumes the
increase will be a multiple of the
rent. See assumptions below?
Required message
{{myForm.IncreasedValue.$viewValue}} is above 600,000 max

Advanced Features

{{type.name}}
Required message
{{myForm.RentInflation.$viewValue}} is below 1% minimum
{{myForm.RentInflation.$viewValue}} is above 10% max
%
Required message
{{myForm.TaxRate.$viewValue}} is below 1% minimum
{{myForm.TaxRate.$viewValue}} is above 1.5% max
%
Look up your tax rate at
www.sanmateocountytaxcollector.org?
Required message
{{myForm.InsuranceRate.$viewValue}} is above 1% max
%
Required message
{{myForm.YearsOccupied.$viewValue}} is below 1 year minimum
{{myForm.YearsOccupied.$viewValue}} is above 120 year max
years
Required message
{{myForm.WeekstoOccupy.$viewValue}} is above 8 week max
weeks
Required message
{{myForm.ManagementRate.$viewValue}} must be above 0% minimum
{{myForm.ManagementRate.$viewValue}} is above 10% max
%

There is an unexpected number in
the information you've provided. Please review and update to see results.

Results

{{Rent - MonthlyCosts[0] | currency : usd : 0}}

Monthly Income After Expenses

{{Rent | currency : usd : 0}} monthly rent and {{MonthlyCosts[0] | currency : usd : 0}} monthly costs
Hover over chart for monthly cost breakdown
${{TotalDevelopmentCostShort}}K

Construction Costs

The cost to build your Second Unit is estimated at {{SqftConstructionCost/ADUSqft | currency : usd : 0}} per square foot with a total cost of {{TotalDevelopmentCost | currency : usd : 0}}.
Hover over chart for construction cost breakdown. Hard costs cover constructing the second unit, both labor and materials. Soft costs are things like architects. Fees are charged by the city.
{{YearsInvestmentRecovered | number : 0}}

Years to earn back your cash investment

You will recover your initial cash investment of {{CashInvestment | currency : usd : 0}} in {{YearsInvestmentRecovered | number : 0}} years (excluding outstanding loan balance and increased value of house).
{{YearsADURecovered | number : 0}}

Year Return on Investment

Once you account for the amount remaining on your loan and the increase in property value, your Second Unit will pay for itself in {{YearsADURecovered | number : 0}} years.
${{IncreasedValueShort}}K

Increase in Home Value

Your Second Unit will increase your home value by approximately {{IncreasedValue | currency : usd : 0}}, assuming the value increases by 8-9 times the yearly rent.
Year 10
Year 20
Year 30
Property value increase
from second unit
{{IncreasedResaleValue[9] | currency : usd : 0}}
{{IncreasedResaleValue[19] | currency : usd : 0}}
{{IncreasedResaleValue[29] | currency : usd : 0}}
Rent collected (cumulatively)
{{CumulativeGrossIncome[9] | currency : usd : 0}}
{{CumulativeGrossIncome[19] | currency : usd : 0}}
{{CumulativeGrossIncome[29] | currency : usd : 0}}
Cumulative net income
(rents minus costs)
{{CumulativeNetIncome[9] | currency : usd : 0}}
{{CumulativeNetIncome[19] | currency : usd : 0}}
{{CumulativeNetIncome[29] | currency : usd : 0}}
Future monthly rents
{{GrossRentalRevenue[9]/12 | currency : usd : 0}}
{{GrossRentalRevenue[19]/12 | currency : usd : 0}}
{{GrossRentalRevenue[29]/12 | currency : usd : 0}}
Monthly costs
{{MonthlyCosts[9] | currency : usd : 0}}
{{MonthlyCosts[19] | currency : usd : 0}}
{{MonthlyCosts[29] | currency : usd : 0}}
Annual tax increase
{{-PropertyTax[9] | currency : usd : 0}}
{{-PropertyTax[19] | currency : usd : 0}}
{{-PropertyTax[29] | currency : usd : 0}}
Average annual return on investment (just using rent)
{{(GrossRentalRevenue[9]/12 - MonthlyCosts[9]) / CashInvestment * 100 | number : 1}}%
{{(GrossRentalRevenue[19]/12 - MonthlyCosts[19]) / CashInvestment * 100 | number : 1}}%
{{(GrossRentalRevenue[29]/12 - MonthlyCosts[29]) / CashInvestment * 100 | number : 1}}%
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