Formula: Base range (by bathroom type) × Scope factor × Finish multiplier × Location adjustment + Feature costs + 20% contingency
Base ranges are national midpoints from verified 2026 industry data.
Scope factors: Minor 0.65×, Partial 1.0×, Full 1.5×
Finish multipliers: Budget 0.7×, Mid-Range 1.0×, Premium 1.5×, Luxury 2.5×
Location: Affordable 0.85×, Average 1.0×, High-COL 1.4×
Contingency (20%): For hidden water damage, outdated plumbing, tile substrate issues.