Welcome to the ADU Calculator! #
This document will help you to set up your Calculator for public use. This document will walk you through how to:
- Research and gather information to adjust your Jurisdiction Parameters and customize the Detailed Report, and
- Enter your assumptions and custom text into the Admin Portal.
We recommend checking the Admin Portal regularly to make sure your Jurisdiction Parameters and Detailed Report are up to date and are providing accurate results for your residents.
Helpful Terms and Documents #
Here are some terms that you will see used throughout this article:
Jurisdiction Parameters/City Configuration #
These are the assumptions that are customizable at the jurisdiction level and feed into the cost estimates produced by the Calculator. They must be updated before launching your Calculator to ensure the cost estimates are accurate for your jurisdiction. They include:
- Max ADU Size – What are the maximum permitted ADU sizes for studio/1-bedroom and 2+-bedroom units in your jurisdiction?
- Rents – What are the average rents for 500 and 1,000 square foot units in your community?
- Local Construction Cost Adjustment – How do construction costs for your jurisdiction compare to your county as a whole?
- Building Permit and Planning Fees – What are typical building permit and planning fees as a percentage of development costs?
- Impact Fees – What are typical impact fees?
Countywide Parameters/Configuration #
These are the assumptions that are set for the entire county that combine with your Jurisdiction Parameters to produce the Calculator cost estimates. The Countywide Parameters are updated regularly including construction costs (annual updates) and interest rates (annual to quarterly updates). These updates will affect the estimates your Calculator produces.
- Countywide base construction costs include the types of construction and systems costs like kitchens, bathrooms, electrical, plumbing and heating. This will be important for you to figure out your Local Construction Cost Adjustment (Local Multiplier) in Step 2.
- Finance defaults include the length of loan, loan interest rate, insurance cost, property tax rate and rental management rate.
- Rent defaults include annual rent increase, average tenant stay and vacancy time for finding new tenants.
- Some of these assumptions, like construction costs and rents, can be modified by customizing your Jurisdiction Parameters.
Admin Portal #
This is the internal platform where you can view and customize your Calculator (and manage your Plans Gallery if you have one). Learn more in the Admin Portal Overview.
Onboarding Form #
The Onboarding Form: Jurisdiction Parameters & City Configuration Assumptions will help you gather what you will need to set up your Calculator Jurisdiction Parameters and Homeowner Detailed Report.
Cost Assumptions Spreadsheet #
The Cost Assumptions Spreadsheet will help you understand how to adjust your local construction costs. You can learn more in the Calculator Construction Costs Help Doc.
STEP 1: Download the Onboarding Form #
You can use the Onboarding Form to collect, record and confirm your jurisdiction assumptions before adding them to the Admin Portal. It can also be used to record, update and track your jurisdiction assumptions as they change over time.

STEP 2: Gather Your Jurisdiction Assumptions and Detailed Report Information #
Using the Onboarding Form, research, gather and track the information you will need to adjust and customize your Jurisdiction Parameters and the Homeowner Detailed Report.
Jurisdiction Parameters #
Your Jurisdiction Parameters are how you manage and customize your Calculator to reflect the local rules and costs associated with building an ADU in your community. These include:
- Jurisdiction Contact Information – Identify all staff members that need access to the Admin Portal. This information will remain private and cannot be seen by users of the Calculator.
- Maximum ADU Size Allowed – Represents the maximum permitted ADU square footage for studio/1 bedroom units and for 2/+ bedroom units in your jurisdiction.
- Rents – Default rents are prepopulated for 500 square-foot and 1,000 square-foot units, which may need to be adjusted based on your local rental market conditions.
- Local Construction Costs Adjustment (Local Multiplier) – Allows you to set local construction costs that adjusts countywide costs on a scale from 0.5 to 2. Building/Permit Fees – Defines building and permit fees as a percentage of development costs, which are usually in the 2-3% range.
- Impact Fees – Aggregates total impact fees for ADUs. Currently, the Calculator only includes fees that apply across the entire jurisdiction.
- Impact Fee Description (External): This is an optional custom paragraph that will appear along with the impact fees estimate.
- Impact Fee Description (Internal): Use this field to store your impact fee calculation details and notes for your own and your staff’s reference.
Homeowner Detailed Report #
The Homeowner Detailed Report provides a downloadable one-page report with details about the project estimate, costs, fees, rents, and information about how choices affect the project budget. Jurisdictions may choose to provide customizable location-specific content including:
- “Custom Intro Text” – This optional customizable text will appear at the top of the report. You can add general information about ADUs in your jurisdiction and include links to resources or information that can aid local homeowners.
- “Other Considerations” – This optional customizable text will appear at the bottom of the report. Consider including additional information about building ADUs in your jurisdiction that were not stated earlier in the report.
STEP 3: Launch the Admin Portal #
- Go to https://admin.aducalculator.org/login.
- Enter the email address that you registered for access
- You will receive an email with a 4-digit code to enter for access.
- Check your spam folder if it doesn’t arrive within a couple of minutes.
NOTE: If you aren’t sure you are registered or if you don’t receive a code, reach out to support@aduaccelerator.org and we can check for you.
Step 4: Enter and Adjust the Inputs from Your Onboarding Form #
Jurisdiction Parameters #
Navigate to Calculator > Jurisdiction Parameters. This tab will open to the City Configuration where you can update local assumptions for ADUs.

Guidance on how to set the assumptions are included along with the editable fields. Make sure to check all the assumptions and update them as needed based on what you recorded in the Onboarding Form.
Click the Save button to save this content.
Detailed Report #
Navigate to Calculator > Detailed Report. This tab will open to the Profile Report Customization page where you can update the custom text for the Homeowner Detailed Report.

Guidance on how to set the assumptions are included along with the editable fields or you can refer to the Onboarding Form if you created custom text in the form.
Click the Save button to save this content.
STEP 4: Test Your Calculator Cost Estimates #
Visit your Calculator and create some example projects to test the cost estimates the Calculator produces. If these look off, adjust your Jurisdiction Assumptions as needed.
If you’re having trouble or need help, email support@aduaccelerator.org.