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Home Planning · reviewed September 11, 2026
Garage Conversion vs Addition Calculator
Compare the estimated cost per added living square foot of converting a garage versus building a new addition using your own cost assumptions.
Quick answer
Garage Conversion vs Addition Calculator
The cheaper project is not necessarily the better project. This calculator isolates project cost and added living area; parking, zoning and property-value effects remain separate decisions.
Formula: Each path = (area × cost per sq. ft. + path-specific extras) × (1 + contingency).
Living area created by the conversion.Your estimated conversion rate.Floor leveling, HVAC, doors/windows or other scope.Living area created by the addition.Your estimated addition rate.Foundation, tie-in, design or other fixed scope.Applied to both paths for a like-for-like comparison.
Enter your numbers and calculate.
How the calculation works
Each path = (area × cost per sq. ft. + path-specific extras) × (1 + contingency).
Every rate, percentage, cost and value assumption shown in the calculator can be changed. Results are scenario math based on your inputs, not quotes, appraisals, code determinations or predictions.
Questions people ask
Does this account for losing the garage?
Not automatically. The result focuses on project cost per added living square foot.
Can the addition and conversion be different sizes?
Yes.
Does the tool know whether a garage can legally be converted?
No. Local requirements must be checked separately.