Standard ADU calculator

ADU cost calculator.

A standard ADU calculator should not start with a blank page. It should use size, finish level, region, site complexity, utility distance, delivery access, permit assumptions, and contingency, then let the buyer replace any planning number with a real quote.

How it works

Standard assumptions first, exact quotes later.

The calculator now follows the common ADU planning pattern: project profile, site conditions, editable line items, planning range, per-square-foot result, and a clear warning that the output is not a contractor bid. For this fold-out product, it keeps the factory package separate from the local site work.

product path site conditions permit boundary prefab ADU cost

1. Project profile

Model path Target square feet California region Finish level

2. Site conditions

Site complexity Utility distance, feet Utility condition Delivery and setting access

3. Editable assumptions

These planning defaults are editable. Replace them when you have a supplier quote, engineer number, city fee estimate, or utility bid.

Factory/build package, $ per sf Delivery + setting override Foundation/site override Utilities override Permits/soft-cost override Contingency percent 12%

Standard fields

What changed from the old version.

The old calculator waited for every line item. This version behaves like the ADU calculators buyers already understand: choose size, region, finish level, site condition, utility distance, and access difficulty, then inspect an automatic cost breakdown.

Square-foot driverUses a visible editable dollar-per-square-foot allowance instead of hiding the unit math.

Site-work driverFoundation, utility distance, and delivery access are separate because they are common ADU budget swing factors.

Range outputShows a planning range around the estimate so the page never pretends the first number is a bid.

Product boundaryKeeps the factory/build package separate from local permits, utilities, foundation, and setting.