How to Use the ADU Calculator
The ADU Cost Calculator is a useful tool that quickly estimates the price of building typical ADU projects in California.
This step by step guide was updated in December 2020 because more cities/counties launched calculators and the interface changed significantly.
Use the links below to explore ADU Construction Cost Calculators from the County of San Mateo, the Napa Sonoma ADU Center, and ADU Marin, and find a sheet that helps you adjust the costs to your nearest Californian city.
You can follow along as I share my screen and explain some of the less intuitive parts of the ADU cost calculator, and what assumptions go into the calculations.
The ADU cost calculators let you play with a lot of variables like square footage of your Accessory Dwelling Unit, the type of construction finish you want to use, the lot access and slope, and much more. I'll walk you through step by step if you have any questions.
Even if you don't know much about construction, you'll be a pro at how to use this website-based calculator.
If you live in San Mateo, Redwood City, Palo Alto, South San Francisco, San Bruno, Pacifica, Menlo Park, and so on, this calculator is made for you: https://bit.ly/adu-calculator-san-mateo
If you live in Santa Rosa, Petaluma, Rohnert Park, Windsor, Sonoma, Healdsburg, Calistoga, St Helena, Napa, or other parts of Napa County and Sonoma County, then this calculator is made for you: https://calculator.napasonomaadu.org/
If you live in Belvedere, Corte Madera, Fairfax, Larkspur, Mill Valley, Novato, Ross, San Anselmo, Sausalito, Tiburon, or the unincorporated parts of Marin County, then this calculator is made for you: https://calculator.adumarin.org/ (and frankly, San Rafael can use it too, you just have to pick another city).
And if you don't live in one of those four counties, use this sheet to convert the results for San Mateo (South San Francisco) to a city closer to you, just by multiplying the result times the percentage in your city's corresponding row of this sheet: https://bit.ly/cost-calc-converter Subscribe for more accessory dwelling unit resources: https://www.youtube.com/channel/UCZ6g...
There are more ways to estimate ADU costs: https://bit.ly/adu-costs-play
And once you've wrapped your head around costs, you might want to start thinking about financing: https://www.youtube.com/watch?v=LyCIJ...
And if you want to read more about Accessory Dwelling Units and how to build one, be sure to check out all the free resources at https://www.how-to-adu.com/adu-articl...
