Conventional vs. incremental home cost calculator

Start with a home you’re looking at, perhaps one listed on Zillow. Enter its asking price and size, and see what you would actually spend over the life of the mortgage compared with building incrementally: a smaller home now, with additions later. The results update as you type.

See the comparison

A home you’re looking at

Start here. A conventional purchase: the full home bought at once with one mortgage.

Asking price ($) From a listing, such as on Zillow Square feet Heated living area

Loan term Interest rate (%)

About this model

The comparison tracks the amount of money the average homeowner actually spends over the life of a conventional mortgage as compared to an alternative incremental path.

Incremental households start with a small, complete home, then add rooms over time, paying for later phases with savings or short loans instead of carrying one large 30-year mortgage. Each later phase is priced at the same cost per square foot as the home you entered, unless you enter your own price for it, raised 3% for each year until it is built, and is counted in the year it is built.

These figures are planning estimates, not a quote or loan offer. The price you enter includes the land, so the same cost per square foot is used for both paths. They leave out closing costs, taxes, insurance, mortgage insurance, and upkeep. Ask us for current construction costs on your site.

A home equity line of credit (HELOC) can also pay for an addition, but its rate changes over time and it often starts with interest-only payments, so its costs aren’t shown here.

Building incrementally

Start with a smaller, complete home and add on later. Unless you enter your own price, every phase uses the same cost per square foot as the home on the left, . Later phases are priced 3% higher for each year until they’re built, to account for rising building costs. If you will help build a phase yourself, enter your own total price for it and the cost per square foot updates as you type.

Phase costs

Summary

Conventional total

Incremental total

Total paid to date

Square feet you live in

Monthly payments, year by year

Monthly loan payments during each year. Down payments and cash phases are paid when each phase is built and are not monthly amounts. Shaded rows are years a phase is built (P1 is phase 1).
Year	Conventional	Incremental	Incremental sf

What would you do with ?

Want to plan a home that grows with you?

Tell us about your site and budget, and we will talk through a first phase and what could come next.

Request a consultation