RULES OF THUMB FOR PAINTING AND ESTIMATING
“Rules of Thumb” are general guidelines and are often used for the purposes of estimating. These do not always give “exact” numbers but are intended to provide a good working number.
Definitions: R – Radius; D – Diameter; LF – Lineal Feet, SF Square Feet; W – Width; H - Height
Estimating Square Footage:
To get Square footage on Caged Ladder | Mutiply LF by | 10 | Handrails | Mutiply LF by | 4 | Grating | Mutiply LF by | 4 | Stairs with 1 Hand Rail | Mutiply LF by | 10 | Stairs with 2 Hand Rails | Mutiply LF by | 15 | Walkway with 1 Hand rail | Mutiply LF by | 15 | Walkway with 2 Hand Rails | Mutiply LF by | 20 | Solid Floor Plate | Mutiply LF by | 15 | Cylinder | Mutiply LF by | D x 3.142 | Sphere | Mutiply | D x D x 3.142 | Circle | Mitiply | R x R x 3.142 | PIPING | 1/2 “ to 3” | Mutiply LF by | 1.00 | 4 | Mutiply LF by | 1.19 | 6 | Mutiply LF by | 1.74 | 8 | Mutiply LF by | 2.26 | 10 | Mutiply LF by | 2.81 | 12 | Mutiply LF by | 3.34 | 14 | Mutiply LF by | 3.665 | 16 | Mutiply LF by | 4,19 | 18 | Mutiply LF by | 4.71 | 20 | Mutiply LF by | 5.24 | 24 | Mutiply LF by | 6.28 | 28 | Mutiply LF by | 7.33 | 30 | Mutiply LF by | 7.85 | 34 | Mutiply LF by | 8.90 | 36 | Mutiply LF by | 9.425 | 42 | Mutiply LF by | 10.10 | Other Shapes | Joists (Treat as solid surface) | Mutiply LF by | 2 x H | Stacks | Mitiply H | Average D *3 | Corrugated Metal 2 ½” | Mutiply LF by | 1.08 x H | Corrugated Metal 1 ¼” | Mutiply LF by | 1.11 x H |
Estimated Losses: Brush or Roller: 10%; Airless Spray: 20%; Conventional Spray: 30%
PAINT CALCULATIONS
Theoretical Coverage 1 mil of 100% Solids Coating covers 1604 ft2/WFT
Practical Coverage Theoretical Coverage x % Loss
Dry Film Thickness = DFT in mils Wet Film Thickness = WFT in milsAll % are by volume and expressed as a decimal i.e. 60% = .60
DFT = WFT x (% Solids) 
Conversion Charts and Paint Thinning Calculations
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