Question 1

How many gallons of paint do I need for a room?

Accepted Answer

Divide the total paintable square footage by the paint's coverage rate (typically 350 sq ft/gal for smooth drywall), then multiply by the number of coats. A standard 12×12 room with 8-foot ceilings needs about 1.5 gallons for two coats after deducting windows and doors.

Question 2

Does primer count toward the total paint quantity?

Accepted Answer

No. Primer and paint are calculated separately because they have different coverage rates. Primer typically covers 300–350 sq ft/gal on new drywall but only 200–250 sq ft/gal on porous substrates like bare wood or stucco. Calculate primer quantity first, then calculate paint quantity for your finish coats.

Question 3

How do I account for multiple coats when calculating paint?

Accepted Answer

Multiply the single-coat quantity by the number of coats. Most color changes and new construction require two coats. Dark-to-light color changes or high-hide situations may need three. Second and subsequent coats typically use slightly less paint because the surface is already sealed, but it is safer to calculate each coat at the full coverage rate.

Question 4

What is the standard coverage rate for interior latex paint?

Accepted Answer

Interior latex paint covers approximately 350–400 sq ft per gallon on smooth drywall. Coverage drops significantly on porous or textured surfaces: wood trim covers 300–350 sq ft/gal, plaster 275–325, concrete 250–300, stucco 200–250, and brick 175–225 sq ft/gal. Always check the manufacturer's data sheet for the specific product.

Substrate	Coverage (ft²/gal)	Why It Differs
Drywall (smooth)	350–400	Smooth, sealed surface absorbs least paint
Wood / Trim	300–350	Grain absorbs paint; depends on species and condition
Plaster	275–325	Porous, textured surface absorbs more
Concrete	250–300	Very porous; first coat absorbs significantly more
Stucco	200–250	Deep texture traps paint; heavy first coat
Brick	175–225	Mortar joints and porous surface; highest consumption

How Many Gallons of Paint Do I Need?

Room Dimensions

Paint Details

Deductions

Results

How coverage rates affect quantity

Need room-by-room calculations?