Cost Estimators
Last Updated: August 2026
All cost estimators run a real pricing model with line-item trade costs, regional labor multipliers, and honest design, permit, and contingency allowances, then show you exactly where every dollar goes.
There are no email forms, no gated results, and no contractor lead selling. You get a number, a breakdown, a realistic range, and a timeline.
If you are trying to add space to your home, start with the comparison table below. It is the fastest way to find out which path actually fits your lot, your budget, and your situation before you spend anything on drawings.
Home Inspection Cost Calculator
Use Home Inspection Cost Calculator
Start here if you are buying. Prices a general inspection by square footage, property type, age, foundation, and market, plus ten add-on tests such as radon, sewer scope, mold, and septic. A 2,200 sq ft modern home on a slab in an average market runs about $436, with a typical range of $392 to $501 and a two-and-a-half to three-hour inspection.
Use it when you are under contract, when you are deciding which add-on tests are worth ordering, or when you want to know whether a house can support the project you have in mind.
Garage Conversion Cost Calculator
Use Garage Conversion Cost Calculator
The cheapest finished square footage you can buy. Prices five uses, from a dry gym or family room up to a fully independent ADU, across one-car to three-car attached and detached garages.
A 450 sq ft two-car garage runs about $56,763 as a gym and about $108,617 as a rentable ADU with a bath, kitchenette, and egress window. Use it when you already have a garage you are willing to give up and you want space fast and cheap.
Home Addition Cost Calculator
Use Home Addition Cost Calculator
The most flexible path, and the one with the widest price range. Prices seven room types including primary suites, family rooms, kitchen expansions, in-law ADUs, sunrooms, bathrooms, and attached garages, across slab, crawlspace, pier, and full basement foundations.
A 500 sq ft primary suite on a slab runs about $153,095, or roughly $306 per square foot. Use it when you have buildable yard, when your first floor layout needs to change, or when you want a basement underneath the new space.
Second Story Addition Cost Calculator
Use Second Story Addition Cost Calculator
For when there is nowhere left to build but up. Prices full second stories, partial pop-ups, over-garage builds, and modular additions, with structural underpinning, staircases, and mechanical scope. A 1,000 sq ft full second story with mid-range finishes runs about $289,190, or roughly $289 per square foot, over 3.5 to 5.5 months of construction.
Use it when setbacks, lot coverage, or a septic field leave you no room to expand outward, or when your yard is the thing you refuse to pave over.
Compare every way to add space
This is the table worth bookmarking. All figures come from the calculators above, using mid-range finishes in an average-cost U.S. market.
| Path | Cost per sq ft | Typical project | Construction time |
|---|---|---|---|
| Garage conversion, dry space | $126 to $150 | $56,763 for a 450 sq ft gym | 1.5 to 3 months |
| Garage conversion, full ADU | $241 | $108,617 for a 450 sq ft unit | 2.5 to 4.5 months |
| Second story, large floor | $260 to $270 | $519,090 for 2,000 sq ft | 4.5 to 7 months |
| Second story, standard floor | $289 | $289,190 for 1,000 sq ft | 3.5 to 5.5 months |
| Ground-floor addition, primary suite | $306 | $153,095 for 500 sq ft | 2.5 to 4.5 months |
| Ground-floor addition, in-law ADU | $332 | $199,090 for 600 sq ft | 3.1 to 5.7 months |
| Ground-floor addition, kitchen expansion | $367 | $183,582 for 500 sq ft | 3 to 5.5 months |
| Ground-floor addition, small bathroom | $575 | $69,032 for 120 sq ft | 2.5 to 4.5 months |
Converting a garage delivers finished space at roughly 40 percent of the cost of building a new room on the ground. The catch is that you are not adding square footage to the property. You are reclassifying space you already own, and you are trading covered parking for it.
What is the minimum you need to spend?
Every path has a floor, and the floors are very far apart.
| Path | Realistic minimum | What that buys |
|---|---|---|
| Garage conversion | about $35,000 | 400 sq ft dry gym or rec room, builder grade, low-cost market, sealed concrete floor, no plumbing |
| Ground-floor addition | about $66,000 | 400 sq ft builder-grade attached garage in a low-cost market |
| Second story addition | about $198,000 | 1,000 sq ft builder-grade floor, rural market, no structural work needed |
A second story has by far the highest entry price of any option. You cannot do a small one cheaply, because opening the roof, setting a staircase, and running a new service panel cost nearly the same whether you add 500 square feet or 1,500. If your total budget is under $200,000, the second story is very likely off the table no matter how much you want it.
Three cost rules that hold true across all calculators
These patterns show up in every model on this page, and understanding them will save you more money than any single line item.
1. Small projects always cost more per square foot.
Fixed costs do not shrink with your floor plan. Permits, mobilization, a bathroom, a heating system, and an electrical panel cost about the same at 400 square feet as they do at 1,200.
| Project | Small version | Large version |
|---|---|---|
| Second story addition | $366/sq ft at 600 sq ft | $260/sq ft at 2,000 sq ft |
| Ground-floor addition | $324/sq ft at 400 sq ft | $258/sq ft at 1,500 sq ft |
| Garage conversion ADU | $346/sq ft at 250 sq ft | $183/sq ft at 800 sq ft |
Before you shrink a project to save money, price the bigger version. Marginal square footage is often the cheapest space you will ever add, frequently less than half your blended rate.
2. Soft costs are 19 to 21 percent, and they scale with structural risk.
Every build calculator here adds a design and permit allowance plus a contingency on top of hard costs. The total is not the same across projects, and the difference tells you something real.
| Project type | Design and permits | Contingency | Total markup |
|---|---|---|---|
| Garage conversion | 8% | 11% | 19% |
| Ground-floor addition | 8.5% | 12% | 20.5% |
| Second story addition | 9% | 12% | 21% |
The markup climbs as the structural stakes climb. A garage conversion works inside an existing shell. A second story changes the load path of the entire building, which means more engineering, more plan review, and more that can be discovered mid-build. Multiply any change in scope by the right factor before you decide. Adding a $8,500 kitchenette to a garage conversion really costs about $10,115.
3. A bid with no contingency line is not a cheaper bid.
It is the same bid with the surprises hidden until they arrive as change orders. When you compare quotes, compare cost per square foot rather than totals, because scopes differ, and always ask each bidder to show their contingency separately.
Which estimator should you use?
| Your situation | Start with |
|---|---|
| You are under contract on a house | Home Inspection Cost Calculator |
| You have a garage you are willing to give up | Garage Conversion Cost Calculator |
| You have open, buildable yard | Home Addition Cost Calculator |
| Setbacks, lot coverage, or septic block you from building out | Second Story Addition Cost Calculator |
| You need rental income from the space | Compare the garage ADU at $241/sq ft against a ground-floor ADU at $332/sq ft |
| You need one more bathroom and nothing else | Check the addition calculator, then seriously consider converting existing space instead |
| Your budget is under $100,000 | Garage conversion is realistically your only path to finished living space |
The right order of operations
Most people run these steps out of order and pay for it. Here is the sequence that saves money.
- Inspect before you decide. A general inspection costs about $436. It tells you the foundation type, the panel capacity, the roof structure, and the sewer situation, which are the four facts that decide whether your project is cheap or expensive. Spending $436 to inform a $289,000 decision is the best return on this entire site.
- Check zoning and setbacks next. This is a free phone call to your planning department, and it can eliminate an entire path in five minutes. Ask specifically about lot coverage, setbacks, height limits, and whether accessory dwelling units are permitted.
- Price all viable paths with these calculators. Do not fall in love with one option before you know what the others cost.
- Hire a structural engineer for a feasibility report if you are going up or removing a load-bearing wall. It typically costs $1,500 to $4,000 and turns the single largest unknown in your budget into a known number. Every contractor you talk to afterward bids from the same facts.
- Get three bids and throw out the outlier. If one number is 30 percent under the others, it is usually missing the permit allowance, the electrical service, or the finish work on the existing side of the house.
What none of these calculators include
Be honest with yourself about these. They are what turn a planned budget into an actual one.
- Temporary housing during a full second story build, often $8,000 to $25,000.
- Replacement storage or parking after a garage conversion.
- Finishing the existing rooms on the other side of any wall you open.
- Landscaping, driveway, and utility repair from excavation and material staging.
- Furnishings and appliances for the new space.
- Property tax reassessment. Permitted work adds finished area to your record.
- Financing costs. Renovation-specific mortgage products let you borrow against your home’s after-improvement value rather than its current value, which is often how projects of this size get funded.
- Change orders. Contingency covers surprises, not upgrades you decide on in month three.
Frequently asked questions (FAQs)
What is the cheapest way to add living space to a house?
Converting an existing garage into dry living space, at roughly $126 to $150 per square foot. A 450 square foot two-car garage becomes a finished gym or family room for about $57,000 in an average market. You are not adding square footage to the property, though. You are converting space you already have.
Is it cheaper to build up or build out?
Building out is usually cheaper per square foot because you skip roof removal, a crane, a staircase, and moving out during construction. Building up wins when your lot, setbacks, or septic field leave no room to expand outward, or when you are unwilling to give up yard.
How accurate are these cost estimators?
Each one models line-item trade costs, applies a regional multiplier, and returns a range from 10 percent below to 15 percent above the midpoint. That range reflects the honest spread between a lean local builder and a full-service design-build firm. They are planning tools for budgeting and bid-checking, not quotes.
Do these calculators collect my information?
No. Nothing you enter is stored, transmitted, or sold. There is no email gate on any result, and we do not sell leads to contractors or inspection companies.
How much should I budget for permits and surprises?
Plan on 19 to 21 percent on top of hard construction costs, depending on the project. Garage conversions land near 19 percent, ground-floor additions near 20.5 percent, and second story additions near 21 percent, because engineering and risk climb with structural complexity.
Which calculator should I use if I am buying a house?
Start with the home inspection calculator, and tell your inspector what you are planning. Ask for photos of the footings, the electrical panel, the roof structure, and the sewer or septic connection. Those four items decide the cost of every other project on this page.
Technical Basis
Each estimator applies regional cost indices to standard trade breakdowns for site work, structure, envelope, mechanicals, and finishes, using published contractor rate structures. Code assumptions follow International Residential Code requirements for egress, ceiling height, and fire separation. Design, permit, and contingency allowances reflect typical general contractor practice and are reviewed as market rates change.
Disclaimer
These tools provide planning estimates, not quotes, appraisals, or engineering documents. Actual costs vary with site conditions, permit fees, zoning rules, labor availability, and material prices. No personal information is collected or sold. Always confirm final scope and pricing with licensed local contractors and inspectors before committing.
About the Author
Qazi Raza – Technical Creator & Researcher
Qazi Raza develops construction, engineering, and home‑improvement calculators by researching verified formulas, industry standards, and authoritative reference materials. His tools are built using data from ASTM specifications, ASHRAE guidelines, NEC tables, building codes, and widely accepted engineering textbooks. Each calculator is designed to help homeowners, DIYers, and contractors make accurate, confidence‑based decisions.