Fieldsheet

Job sheets for the materials you actually buy.

Paint, in gallons and quarts

Walls, minus the doors and windows, times the coats, divided by a coverage number that comes from a product data sheet. Primer is its own line. The cans are rounded only at the end.

Starts at 0%. The 350 sq ft/gal default is already the low end of SuperPaint’s range. Add percent for spray loss; Behr says the printed coverage leaves spray out.

Job sheet

Fieldsheet paint job sheet

12 ft × 10 ft room, walls 8 ft. 2 finish coats.

  • Walls352 sq ftBoth long walls and both short walls
  • CeilingNot included
  • Openings subtracted44 sq ft1 door, 2 windows
  • Net area308 sq ftNo extra percent added.
  • Finish paint2 gal1.76 gal at 350 sq ft/gal × 2 coats, before rounding to cans.
  • Primer1 gal0.77 gal at 400 sq ft/gal × 1 coat.
Fieldsheet paint job sheet
12 ft × 10 ft room, walls 8 ft. 2 finish coats.

Walls: 352 sq ft (Both long walls and both short walls)
Ceiling: Not included
Openings subtracted: 44 sq ft (1 door, 2 windows)
Net area: 308 sq ft (No extra percent added.)
Finish paint: 2 gal (1.76 gal at 350 sq ft/gal × 2 coats, before rounding to cans.)
Primer: 1 gal (0.77 gal at 400 sq ft/gal × 1 coat.)

Area, then cans

Four walls are 2 × (length + width) × height. That counts each wall once. A ceiling, if you check it, is length × width and is not subtracted when you remove a window. Openings are width × height × how many, in feet. Net area times coats, divided by square feet per gallon, is the paint. Gallons and quarts are the purchasable split: leftover quarts that add up to a gallon become a gallon.

A 12 by 10 room with 8-foot walls

Walls: 2 × (12 + 10) × 8 = 352 square feet. One 36 × 80 inch door is 20 square feet. Two 36 × 48 inch windows are 24. Net is 308 square feet. Two coats at 350 square feet per gallon is 1.76 gallons, which buys as 2 gallons. Primer at 400 square feet per gallon is 0.77 gallons, so 1 gallon. The raw primer number is under a gallon; the can on the shelf is not.

The ceiling is off in that example. Turn it on and you add 120 square feet, which at two coats is most of another gallon. Forgetting the ceiling is how a bedroom job dies with the roller still wet.

Where 350 and 400 come from

SuperPaint Interior, flat and satin, both say 350–400 square feet per gallon at 4 mils wet. Behr Premium Plus satin says 250–400, and the sentence under it excludes spray loss. The default sits at 350 so a brushed or rolled wall is inside both sheets without pretending every color hides in one coat. Primer is Sherwin-Williams Multi-Purpose B51-450 at 400 square feet per gallon, one coat, because that PDS is written as primer plus two finish coats. If you are repainting a sound finish in a similar color, turn primer off.

The extra-percent box starts at zero. Raising coverage from 400 to 350 already buys more paint than the optimistic end of the SuperPaint line. Use the percent when you spray, which Behr explicitly leaves out of the coverage, or when you are cutting in a lot of trim the wall math ignores.

Mistakes

FAQ

How many coats should I buy?

The Sherwin-Williams primer system sheet calls for one coat of primer and two coats of a topcoat. This page starts there. Behr also says some colors need more than one coat to hide, so a deep red over white is a reason to add a coat, not a reason to change the room size.

Why is coverage 350 instead of 400?

SuperPaint’s data sheet says 350 to 400 square feet per gallon at 4 mils wet. Behr Premium Plus says 250 to 400, and that range does not include paint lost to spraying. Starting at 350 stays inside both published ranges and leans toward the roller, not the sprayer. Type 400 if you are on the high end of the sheet, or 250 if the surface is rough and thirsty.

Do I subtract windows?

Yes. A 3-foot by 4-foot window is 12 square feet you will not paint. Two of them and a 36 by 80 inch door (20 square feet) come off the walls. Leaving them in buys a phantom gallon on a small room.

Is primer the same coverage as the finish?

Not on the sheets used here. Sherwin-Williams Multi-Purpose primer is 400 square feet per gallon. The finish default is 350. The sheet keeps them on separate lines so you don’t buy primer with the wall-paint math.

Sources

  1. Sherwin-Williams SuperPaint Interior Latex Flat, PDS — Coverage 350–400 sq ft per gallon at 4 mils wet, 1.4 mils dry.
  2. Sherwin-Williams SuperPaint Interior Latex Satin, PDS — Same 350–400 sq ft per gallon coverage at 4 mils wet.
  3. Behr Premium Plus Interior Satin Enamel No. 7050, TDS — Coverage 250–400 sq ft/gal depending on method and porosity. Does not include loss from spraying. Some colors need more than one coat.
  4. Sherwin-Williams Multi-Purpose Interior-Exterior Latex Primer-Sealer, B51-450 — Coverage 400 sq ft per gallon at 4 mils wet. The spec layout is one coat of this primer and two coats of topcoat.