This section is designed to match how readers think when estimating a Detached ADU Construction budget. Follow these steps in order for the clearest results.

Step 1: Enter Your ADU Size

Start by entering your planned ADU size in square feet. If you’re unsure, use a common baseline like:

• 400–500 sf for a studio
• 550–750 sf for a 1-bedroom
• 800–1,000+ sf for a 2-bedroom

Even small changes in square footage can shift the estimate noticeably, so it helps to start with your best guess.

Step 2: Choose Your Finish Level

Next, choose the finish level that matches your goals. If you plan to rent the unit, many owners choose mid-range for durability and tenant appeal. If it’s for family, your finish level may depend on comfort and long-term value.

This choice sets the calculator’s base $/sf range, which becomes the foundation of the estimate.

Step 3: Select Your California Region

Pick your California region to align the estimate with your local market. This helps avoid the common problem of using a generic national average. Even within California, the same ADU plan can price differently due to labor costs and local demand.

The calculator applies a regional multiplier so the estimate feels more location-aware.

Step 4: Choose Number of Stories

Select single story or two story. If you’re planning a smaller ADU but want to preserve yard space, two-story designs can make sense. Just keep in mind that complexity often increases, which is why the calculator adjusts the cost upward for two-story builds.

Step 5: Choose Bedrooms

Select the number of bedrooms (or studio). Bedrooms can impact:

• plumbing and fixture counts
• HVAC sizing
• electrical layout
• interior wall framing

This isn’t always a huge jump, but it can increase costs as the layout becomes more complex.

Step 6: Choose Lot Condition

Select the lot condition that best matches your property. If your lot is steep or has difficult access, choose the closest match. This helps the estimate include real-world challenges that many homeowners forget to budget for.

Step 7: Select Utility Distance

Choose the utility distance to the main house. If you don’t know exact feet, choose a general category. This step helps capture trenching and run-length impacts that are very common in detached ADU builds.

Step 8: Click “Calculate Detached ADU Cost”

Once the key inputs are set, click the calculate button. The results area should show:

• an estimated total
• a low and high range
• total cost per square foot
• a simple breakdown

This gives users a usable starting point for planning and contractor conversations.