How to Calculate Trim and Baseboard Linear Foot Paint

To convert trim linear feet to square footage: multiply total linear feet by the average trim width in feet (e.g., a standard 4-inch baseboard is 0.33 ft wide; 300 linear feet × 0.33 ft = 100 sq ft). One quart of semi-gloss trim enamel covers 90 to 100 sq ft with two coats. For an average 1,500 sq ft home with 400 linear feet of trim, you need approximately 1 gallon of trim paint.

Painter applying white semi-gloss enamel paint along detailed wooden baseboard molding with an angled sash brush

Published 2026-03-01 · Updated 2026-03-01 · 8 min read

Trim Width Conversion Multipliers

Trim is ordered in linear feet, but paint covers square feet. Convert your molding dimensions using these standard widths:

• 3.25" Baseboard: Multiply linear feet by 0.27.

• 4.5" Baseboard: Multiply linear feet by 0.375.

• 5.25" Baseboard / Crown: Multiply linear feet by 0.44.

• Door Casing (both sides of frame): Average 35 linear feet (approx. 12 sq ft) per standard door opening.

Worked Example: Whole House Trim (450 linear ft of 4.5" baseboard + 8 doors)

Calculating enamel paint for baseboards and door casings for 2 coats of semi-gloss white urethane acrylic.

Purchase 2 gallons of premium enamel to cover all trim and doors with sufficient paint for future scuff maintenance.

Should baseboards be painted before or after installing carpet/flooring?

Paint baseboards with 1 full coat before installation, nail in place, caulk nail holes and seams, then apply a final finish coat with an angled sash brush.

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