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Paint

What it's for

Working out how much paint and primer to buy for a list of rooms. You walk away with gallons for the walls, gallons for any ceilings, primer, and a material list that turns each figure into cans to buy. The drawing unfolds the first room's walls into one strip so you can check the areas. It is an order quantity, not a code check.

Step by step

The example is the screen as it opens: one 12' by 10' room with 9' walls, two coats on a smooth surface, primer on, no openings entered and no ceiling.

Paint inputs at their defaults: SURFACE Smooth (Textured beside it), COATS 2 with a stepper, SQ FT PER GALLON 350 sq ft/gal, INCLUDE PRIMER on, then ROOMS with ROOM 1 and its trash button, LENGTH 12' 0", WIDTH 10' 0", HEIGHT 9' 0", DOORS 0, WINDOWS 0, INCLUDE CEILING off, and ADD ROOM. The answer bar under the title reads ≈ 2.49 gal walls, with ≈ 1.45 gal primer under it. 1 2 3 4 5 6 7 8
The paint job first, then one block of inputs for each room. Waste factor is below Add Room.
  1. SURFACE — Smooth or Textured. A textured wall takes more paint, so the wall coverage rate drops when you pick it. Leave it at Smooth.
  2. COATS — finish coats on the walls and ceilings. 2 here.
  3. SQ FT PER GALLON — the wall paint's coverage, as printed on the can. Until you type yours it reads 350 for a smooth wall and 300 for a textured one: the low end of what makers print (250 to 400), so a cheaper paint is not left short. Type your can's figure.
  4. INCLUDE PRIMER — on adds one coat of primer over everything you are painting. Turn it off for a repaint that does not need it.
  5. Under ROOMS, measure the room wall to wall along the floor for LENGTH (12' 0") and WIDTH (10' 0"), and floor to ceiling for HEIGHT (9' 0").
  6. DOORS and WINDOWS — count the openings. Each one takes a standard allowance off the wall area (20 sq ft a door, 15 a window). Both open at 0, which paints the walls as if they were solid. If the openings come to more than the walls, the screen says so and shows no gallons until you fix the count.
  7. INCLUDE CEILING — on if you are painting the lid in this room. It opens off.
  8. For another room, tap Add Room. The trash can at the top right of a block removes that room.
  9. WASTE FACTOR — the extra for the tray, the roller and touch-up, in steps of 5%. It opens at 10%.
  10. Read RESULTS: ≈ 2.49 gal walls, ≈ 1.45 gal primer, 396 sq ft net area, walls 350 sq ft/gal. The ≈ means the two decimals are rounded: 396 × 2 coats × 1.10 ÷ 350 is 2.489.
  11. Check the unfolded elevation: four walls, 108, 90, 108 and 90 SF, 44' 0" around.
  12. Read MATERIALS for the cans: wall paint, buy 2 gal + 2 qt; primer, buy 1 gal + 2 qt. The quantity beside each can count has the same two decimals as the results. BASIS & WHAT WAS ASSUMED states the coverage per gallon for each surface, the area taken off per door and window, and the rounding to gallons and quarts.
  13. Save or share the job with the buttons at the foot of the screen.
Paint scrolled down, with ≈ 2.49 gal walls repeated in the answer bar under the title. The bottom of the results card shows the BASIS & WHAT WAS ASSUMED row and the link Check before you cut · Measure twice. Below is the UNFOLDED ELEVATION of room 1, four walls of 108, 90, 108 and 90 SF, 9' 0" high over a 44' 0" perimeter, with the notes 396 SF WALLS; NO OPENINGS ENTERED — NO DEDUCTION; SMOOTH 2 COATS · PRIMER 1 COAT · +10% WASTE; WALLS ≈ 2.49@350 · PRIMER ≈ 1.45@300 GAL; BUY WALLS 2G+2Q · PRIMER 1G+2Q, and the title strip UNFOLDED ELEVATION, ROOM 1, NOT TO SCALE. MATERIALS reads Wall Paint — buy 2 gal + 2 qt, ≈ 2.49 gal, and Primer — buy 1 gal + 2 qt, ≈ 1.45 gal. Under them a dimmed SHARE PDF with a list icon at its right end sits beside a lit SAVE, with the line Enter your own measurements to export. 10 11 12 13
The check and basis row, the unfolded elevation, the cans to buy, and the save and share buttons.

Reading the results

The headline is wall paint in gallons for every room together, with your coats and waste in it. It also shows in a strip under the title whenever the results card is scrolled off screen.

Ceiling and primer. A ceiling line appears only when at least one room has INCLUDE CEILING on. The primer line appears only while INCLUDE PRIMER is on. Primer is one coat, whatever COATS says — the drawing notes read PRIMER 1 COAT.

Net area and coverage. Net area is walls plus included ceilings, after the door and window allowances. The rate beside it is labelled walls on purpose: it is the wall paint rate only. The drawing prints each rate on the figure it produced — in the example WALLS ≈ 2.49@350 · PRIMER ≈ 1.45@300 GAL. The wall rate is your SQ FT PER GALLON; check the ceiling and primer rates against the cans you are buying.

The drawing is one room, the one PLAN SHOWS picks once there are two rooms or more (room 1 otherwise), its four walls laid out flat in one strip, each with its area above and its length below. With no openings entered it says so: NO OPENINGS ENTERED — NO DEDUCTION. The gallons in the notes are for the whole job, not just the room drawn. Pinch to zoom, or tap the expand button at the top right to open it full screen. See Reading the drawing.

Materials rounds each figure to cans: gallons plus quarts to buy, with the quantity beside it.

SHARE PDF sends a sheet with the drawing, your inputs and the material list. The list icon at the right end of the same button sends the material list alone. SAVE puts the job in History. SHARE PDF and the list icon in it stay dim until you change at least one input. SAVE stays lit, but while every input is still a default a tap only answers Enter your job's numbers first and saves nothing.

Paint is a Pro calculator, and sharing a PDF and saving to History are part of Pro too. This help is free. See Free and Pro.

Common mistakes