MC360 // Interiors & Paint
HOW MUCH PAINT?DOWN TO THELAST GALLON.
How much paint do I need for a room? One gallon covers about 350 square feet — but coats multiply, primer is separate and ceilings are their own line item. Enter the room dimensions and get gallons for walls, ceiling and primer in one pass.
The Instrument
The Paint Calculator, up close
Inputs
Outputs
Opens the live calculator on matcalc360.pro
Run your own numbersProcess
Three steps. Zero guesswork.
Enter your measurements
Length, width, depth, pitch — the numbers you already pace off on site. No blueprints, no signup, no spreadsheet.
Calculate materials
The calculator applies the right formulas, density factors and waste allowances for your specific material.
Get your results
Squares, yards, tons, boards or sheets — a clean order list you can hand straight to the supplier.
Field Guide
GALLONS, COATS AND COVERAGE — WITHOUT LEFTOVERS
Coverage starts at 350 square feet
One gallon of quality interior paint covers 350–400 square feet per coat on smooth drywall. Wall area is perimeter times height minus doors and windows — typically 40 square feet of openings per room. Divide adjusted area by coverage and you have gallons per coat.
- 1 gal ≈ 350–400 sq ft per coat
- Walls = perimeter × height − openings
- Textured walls cut coverage ~20%
Coats multiply — primer is separate
Two coats is the honest default for color changes. New drywall or dark-to-light transitions need a dedicated primer coat first — primer covers less per gallon (300 sq ft) but seals the surface so the finish coats actually hit their coverage rating.
- 2 coats for color changes
- Primer: new drywall & drastic changes
- Primer ≈ 300 sq ft per gallon
Ceilings and trim are their own list
Ceiling paint is a different product — flat, spatter-resistant, usually white — figured from length times width. Trim paint covers baseboards, casings and doors; a gallon handles the trim of several average rooms. Round up, never down: one sealed leftover gallon beats one emergency quart.
- Ceiling = length × width, flat white
- 1 gal trim paint ≈ 3–4 rooms
- Round up to full gallons
Keep calculating
THE COVERAGE RULE
350
square feet per gallon per coat — the number behind every paint estimate
Related Calculators
Keep the takeoff going
FAQ
Questions from the field
Straight answers on units, waste factors and ordering — the details that decide whether the job finishes on the first delivery.
Ready when you are
STOP GUESSING.START BUILDING.
Free. No signup. Built for the jobsite.