A lot of ADU builder websites have a cost calculator: pick a size, pick a finish level, get a range. It feels helpful, and it does get clicks. But in our own sales, the first question a homeowner asks isn't what it costs. It's whether they can build one on their lot at all.

If your website tool answers the second question first, you get a different kind of inquiry.

The problem with price-first calculators

  • The number is generic. Site work, utilities, access and local fees move the price more than finish level does, and a calculator can't see any of that. A homeowner who anchors on the low end of a range is harder to close later.
  • It skips feasibility. Someone with a lot that can't fit a detached unit still gets a price and still fills out the form. That's a site visit you didn't need.
  • It doesn't tell you anything. The inquiry arrives with a size and a finish level, not an address, a parcel or a reason to believe the project is real.

What homeowners want to see first

In the order they usually ask:

  1. Can I build one here? Their lot, the zone, and whether a detached or attached unit is allowed.
  2. Where would it go? The setbacks drawn on their own yard, so the buildable area is visible.
  3. Which of your plans fit? Your actual plans placed on their lot, not a generic box.
  4. Then roughly what it costs, with the caveats that come with their site.

A tool that walks through that order keeps the homeowner on your site longer, and the people who reach the end have already done the first pass of your qualification.

What the builder should get with the inquiry

The point of the tool is a better first conversation. A good inquiry includes:

  • the address and parcel;
  • the zone and the ADU rules that were applied;
  • the buildable area and which of your plans fit;
  • what the homeowner was interested in (detached, attached, garage conversion);
  • anything flagged for a site visit (slope, easements, septic).

With that, the first call is about their project instead of about whether there is one.

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What the tool should not do

Be clear about the limits. A website lot check is a starting point, not a permit and not a bid. It reads public parcel data and the local code, which can be out of date or miss an easement. Say so on the page, and say that the city's plan review is the final word. Homeowners trust a tool that tells them where its answer stops.

Keep the calculator, change the order

If you already have a cost calculator, you don't have to remove it. Put the lot check in front of it, so the price comes after the homeowner has seen what fits. The range will mean more, and the inquiries will come with an address.

How we do it

We built ADU Insights for our own ADU company in Western Colorado because we were doing this check by hand on every lead. A homeowner types their address on the builder's website and sees their lot, the local rules, and which of that builder's plans fit, and the builder gets the property details with the inquiry. If you build ADUs and want to try it on your own site, see how it works for builders.

This is sales and construction guidance, not legal advice. Confirm local rules with the jurisdiction before you price a job.