© Infrastructure Health & Safety Association (IHSA)
42 • Institute for Work & Health (IWH)
Example 2:
Calculate the weight in kilograms of a steel plate with the following dimensions.
Step 1: Calculate the area.
Convert feet and inches to decimal feet
Note: To convert feet and inches to decimal feet, do inches ÷ 12.
5" ÷ 12 = 0.417'
3' 5" = 3.417'
Area = πr2 = 3.14 × 3.417' × 3.417' = 36.66229146 ft2
Note: 3.14 was used for π. If you use 3.14159 or the π button on the calculator, you will
get a slightly different answer.
Step 2: Locate the unit weight in Table 1.3 Weights of Materials (Based on Surface
Area).
Steel plate (per inch of thickness) = 40 lbs/ft
2
Step 3: Calculate the weight.
Convert fraction of an inch to decimal inches.
Note: To convert a fraction to decimal inches, always do top ÷ bottom.
⅝" = 5 ÷ 8 = 0.625"
Weight = area × thickness in inches × 40 lbs/ft
2
= 36.68088711 ft2 × 0.625" × 40 lbs/ft
2
= 917.0221777 lbs
Step 4: Convert lbs to kilograms.
1 kg = 2.2 lbs
Note: To convert pounds to kilograms, divide by 2.2.
To convert kilograms to pounds, multiply by 2.2.
917.0221777 lbs ÷ 2.2 lbs/kg = 417 kg
