Garage Conversion Calculator
Calculate the complete cost to convert your existing garage into living space — from a basic room to a fully permitted ADU. Compare all conversion scopes, understand permit requirements, and see your true ROI.
Side-by-side comparison of all conversion scopes for your Double Car (2-car) (480 sqft) at Mid-Range finish level.
| Scope | Cost Range | Your Est. | Value Added | Net Gain | Rental/mo |
|---|---|---|---|---|---|
| Basic Room | $5,000–$15,000 | $10,000 | $8,000 | -$2,000 | — |
| Bedroom + Bath | $15,000–$30,000 | $22,500 | $20,000 | -$2,500 | — |
| Full Apartment | $25,000–$50,000 | $37,500 | $28,000 | -$9,500 | $1,200/mo |
| Permitted ADU | $40,000–$80,000 | $60,000 | $48,000 | -$12,000 | $1,500/mo |
Garage Conversion: The Highest-ROI Home Improvement?
Converting an existing garage to living space is fundamentally different from building an addition. You're working with an existing structure — the foundation, roof, and walls are already there. That head start makes garage conversions one of the most cost-effective ways to add living square footage to your home.
Why Garage Conversions Make Financial Sense
Lower cost per sqft than additions: A standard home addition runs $150–$300/sqft fully installed. A garage conversion runs $20–$100/sqft depending on scope. The structure is already built.
High value-add potential: Living square footage is what appraisers and buyers use to compare homes. Converting a 400+ sqft garage can add $60,000–$120,000 in value on a $400,000+ home — often exceeding the conversion cost.
Rental income opportunity: A permitted ADU (accessory dwelling unit) can generate $800–$2,000/month in rental income, paying back the conversion cost in 5–10 years while generating ongoing income.
Garage Conversion Cost Formula
Essential Work = Insulation+Drywall ($3–5/sqft) + Flooring ($2–4/sqft) + Electrical ($1–3K) + HVAC ($2–5K) + Plumbing ($3–8K if bath)
Value Added = Added Sqft × (Home $/sqft × 0.60) OR Home Value × Scope Premium %
Net Gain = Value Added − Conversion Cost
ADU Payback (yrs) = Total Cost ÷ Annual Rental Income
Example: Double-Car Garage → Bedroom + Bathroom
480 sqft Double Garage | Mid-Range Finish | $400K Home
| Insulation + Drywall (480 sqft × $6) | $2,880 |
| LVP Flooring (480 sqft × $4) | $1,920 |
| Electrical (outlets, lights, panel) | $2,000 |
| Mini-Split HVAC | $3,500 |
| Bathroom plumbing rough-in + fixtures | $5,500 |
| Egress window | $1,200 |
| Painting, trim, doors | $1,500 |
| Permits and inspections | $1,200 |
| Total Conversion Cost | $19,700 |
| Home value added (~$222/sqft × 480 × 0.6) | $63,936 |
| Net Value Gain | +$44,236 |
This is a strong ROI project — for every dollar invested in the conversion, the home gains roughly $3.25 in value. The actual return depends heavily on your local market's home price per square foot.