How accurate is the home addition cost calculator?

It provides a planning-level estimate based on your project size, finish selections, and local construction costs for 2026. Final costs depend on contractor pricing and site conditions.

Is the home addition estimate free?

Yes, basic planning-level estimates are free. For users requiring contractor-ready material lists and labor breakdowns, a Pro Report upgrade is available.

Can I estimate different addition sizes?

Yes. Remodelum allows you to adjust the square footage and layout of the addition to build a realistic renovation budget.

Do I need an account to save my estimate?

A free account allows you to save scenarios, while a Pro account unlocks advanced budgeting and tracking tools.

How much does it cost to add a 20x20 room?

A 400 sq ft (20×20) room addition typically costs between $60,000 and $160,000 in 2026, depending on foundation type, finishes, and whether plumbing or electrical work is involved. Use our calculator for a ZIP-code accurate estimate.

How much does a second story addition cost?

Adding a second story typically costs $100,000–$400,000+ depending on the existing structure, square footage, and local labor costs. It requires significant structural reinforcement and is one of the most complex addition types.

Home Addition Cost Calculator (2026)

Addition Type	Low Tier	Mid Tier	High Tier
Bedroom Addition	$40,000	$90,000	$180,000
Bathroom Addition	$25,000	$60,000	$130,000
Sunroom / Enclosed Porch	$20,000	$45,000	$100,000
Second Story Addition	$100,000	$200,000	$400,000+
Garage Conversion	$15,000	$35,000	$75,000

COST BY SQFT

Room Addition Cost Per Square Foot

When planning a layout extension, calculating your baseline home addition cost per square foot helps set a realistic starting budget. On average, a structural addition runs anywhere from $150 to $450+ per square foot depending on the architectural complexity, utility requirements, and selections.

Calculate My Room Addition Cost for Free

  
        Addition Style
        Low Tier
        Mid Tier
        High / Luxury
      
        Standard Room / Bedroom
        $150 – $200 / sq ft
        $200 – $320 / sq ft
        $320 – $450+ / sq ft
      
        Bathroom Addition
        $250 – $350 / sq ft
        $350 – $500 / sq ft
        $500 – $750+ / sq ft
      
        Sunroom / Enclosed Porch
        $125 – $175 / sq ft
        $175 – $275 / sq ft
        $275 – $400+ / sq ft
      
        Second Story Bump-Up
        $200 – $275 / sq ft
        $275 – $400 / sq ft
        $400 – $600+ / sq ft

Addition Style	Low Tier	Mid Tier	High / Luxury
Standard Room / Bedroom	$150 – $200 / sq ft	$200 – $320 / sq ft	$320 – $450+ / sq ft
Bathroom Addition	$250 – $350 / sq ft	$350 – $500 / sq ft	$500 – $750+ / sq ft
Sunroom / Enclosed Porch	$125 – $175 / sq ft	$175 – $275 / sq ft	$275 – $400+ / sq ft
Second Story Bump-Up	$200 – $275 / sq ft	$275 – $400 / sq ft	$400 – $600+ / sq ft

DECOND STORY HOME ADDITION

Second Story Addition Cost Calculator

Building up instead of out is an excellent way to double your square footage without sacrificing valuable yard space. However, utilizing a second story addition cost calculator involves tracking hidden structural elements that standard ground-level expansions completely bypass.

Calculate My Story Addition Cost for Free

On average, adding a full second level costs between $200 and $400 per square foot, totaling roughly $100,000 to $400,000+. When evaluating a vertical "bump-up" project, your calculator matrix should account for these three specific vertical cost drivers:

Foundation & Main Level Reinforcement Your existing foundation and main-floor walls were likely built to hold only a roof, not an entire second level. A structural engineer must evaluate your home; if reinforcements are required, pinning down the foundation or beefing up main-level studs can add 15% to 25% to your base budget.

Staircase Footprint and Floorplan Loss Building up means losing space down below. Framing a code-compliant staircase requires sacrificing roughly 80 to 120 square feet of your current first-floor layout, which usually triggers a partial first-floor remodel.

Roof Demolition & Weather Protection Unlike a ground addition, a second story requires tearing off your home’s existing roof completely. Specialized tarping, heavy-duty weatherproofing, and rapid rough-framing labor are factored heavily into the upfront costs to protect the open structure from sudden rain damage.

COST CATEGORIES OF A HOME ADDITION

Main cost categories of your Addition Remodel

This includes site survey, soil testing, excavation, grading, and other site-related work required for the addition
This includes pouring the foundation, installing footings, framing, roofing, and other structural work necessary for the addition
This includes siding, roofing, windows, doors, and other exterior finishes to match the existing house
This includes insulation, drywall, flooring, paint, and other finishes for the interior of the addition
This includes installing new heating, ventilation, and air conditioning systems
This includes work for lighting, outlets, and appliances
his includes installing new plumbing fixtures, piping, and connections for the addition
This includes decorative finishes, such as trim work, paint, flooring, and cabinetry, to complete the look of the addition

REMODELUM’S TOOKLIT

Sign Up and access Remodelum’s Full Renovation Toolkit

Everything you need from first number to final payment, in one place

01

Estimate your costs

Get a ZIP code–accurate cost breakdown before talking to a single contractor.

02

Iterate your scope

Adjust materials, room size, and finishes to see how changes move your budget.

03

Save your project

Store your estimate, track versions, and revisit at any time.

05

Track costs in real time

Log invoices and payments as work progresses. Always know where you stand.

06

Store documents

Attach contracts, invoices, and permits. Everything in one place.

Methodology

How Our AI Generates Your Estimate

Learn how Remodelum uses real project data to generate ZIP code–accurate estimates.

What stage are you in?

RENOVATION COST CALCULATOR METHODOLOGY

Stop guessing your budget with costs/ square feet

How our AI delivers accuracy:

National Benchmarking: We start with real-world U.S., Canadian and Rest of the World cost standards.
ZIP-Code Localization: Our models adjust for your local labor market and cost-of-living indices.
Visual Precision: We use proprietary models to analyze your project photos and specific scope/ description, refining the estimate to match your unique home.

AI Renovation Cost Estimator

WHY REMODELUM’S ESTIMATE IS BETTER

Why most renovation cost estimates fall short

No two renovations are the same.
The cost of a renovation depends on the scope, the condition of the property, and the decisions made along the way. Generic averages can’t account for these differences.
Remodelum tailors each estimate to the specifics of your project and the current state of the property — not just the type of renovation.
Renovation costs vary dramatically by location.
Labor rates, material pricing, and permitting costs differ from one market to another. That’s why national averages often miss the mark.
Remodelum uses zip-code level data to tailor renovation cost estimates, reflecting local conditions rather than broad assumptions.
A lump-sum estimate doesn’t help you make decisions.
When planning a renovation, tradeoffs are unavoidable — materials vs. labor, finishes vs. scope, budget vs. timeline. Without a breakdown, it’s impossible to understand where money is going.
Remodelum provides a detailed, category-level estimate so you can evaluate tradeoffs and compare contractor quotes more effectively.
Estimating is only the beginning.
Once a renovation starts, costs change. Materials get adjusted, scope shifts, and new decisions appear. An estimate that lives in isolation quickly becomes outdated.
Remodelum turns your estimate into a live renovation budget — so the same breakdown you plan with is the one you track as work progresses.

ADVANTAGES OF HAVING AN ACCURATE COST CALCULATION

Why accurate renovation estimates matter

Most renovation budgets fail because homeowners rely on generic averages.

Every renovation project is different. The cost depends on the size of the property, the scope of work, the quality of finishes, and the local construction market.

Remodelum generates a personalized renovation cost estimate based on:

• Your project's scope and rooms involved

• The quality of finishes you select

• The size of the property

• Local construction costs at the zip-code level

The result is a realistic renovation budget you can use to compare contractor quotes and plan your project before construction begins.

KEY FEATURES

Key Features of Remodelum’s Renovation Cost Estimator

Learn more

Labor and material costs adjusted to the specific zip-code of the renovation
Estimate kitchen, bathroom, whole-home renovations and more
Includes breakdown for main cost categories of your renovation
Customize materials, finishes, location and other cost categories
Use the estimated cost of your renovation as a first step to plan and track your entire project

HOW IT WORKS

How this calculator works?

Basic details of your renovation
So we can tailor it to your personal needs using our AI engine
Understand HOW MUCH each category will cost and WHY
Once your renovation starts, Remodelum helps you track actual expenses, payments, and invoices against your estimate — so you always know where your budget stands.

START WITH AN ACCURATE CALCULATION

Why use a home remodeling cost estimator?

Understand the expected cost of your renovation
Add or remove activities into your scope of work depending on your budget
Assess if there is room for negotiation in your contractor’s quotes
The home renovation calculator is the first step in the overall planning phase - Compare quotes and find contractors

Planning additional rooms or a full renovation? Remodelum also covers kitchen remodel costs, bathroom remodel costs, and whole house renovation estimates.

Want to understand how Remodelum generates localized estimates? See how our AI renovation cost estimator works

FAQs

Room additions typically range from $120 to $250 per square foot, depending on location and materials.
Yes, second-story additions cost more—usually $200 to $400 per square foot—due to structural engineering and roofing modifications.
asic single-room additions with minimal plumbing and finishes are usually the most cost-effective.
Yes, most jurisdictions require building permits for room or home additions. Your contractor should factor this into your estimate.
Second-story additions often require structural reinforcements and cost more per square foot. Use the calculator to compare both scenarios instantly.
Yes, Remodelum supports different room types, including sunrooms, garages, and master suites.
Yes. You can estimate costs without signing up. Optionally, create a free account to save and compare estimates.

Home Addition Cost Calculator — Free 2026 Estimates by ZIP Code

Typical 2026 costs by addition type