T.W. Reiss, Inc. Handy Reference

Calculating Quantity or Volume

This section is to help you determine how much material to order, how long it will take to pump the water out of a pool or basement, or how much something weighs.

The first step in determining the volume of an object is to determine its square area in one plane. We will use a swimming pool that is 20' x 40' for an example. If we multiply the length by the width we get 20 x 40 =800 so the area is 800 square feet, To determine how many gallons of water is in the pool we to multiply that area by the average depth. We will use 4' for our imaginary pool, so 800 x 4 = 3200 cubic feet of water. There is 7.5 gallons in one cubic foot, so we must multiply 7.5 x 3200 to determine that our pool holds 24,000 gallons of water. If we wanted to know how much paint to buy we would need to know the total surface area, which would be the 800 square ft. on the bottom, plus the area of the walls. To determine the area of the walls, the perimeter 20+40+20+40=120 multiplied by the average depth 4x120=480. So we need to buy enough paint to cover 1280 square feet

These concepts can be applied to just about any shape or object. If the shape is irregular, just break it down into a series of familiar shapes, rectangles, circles, ellipses, or triangles, and add all of the areas together. Below is a list of the formulas for calculating the area of most shapes that you might encounter. To get volume, multiply the area by the depth, just remember to use all the same units, don't multiply feet by inches, etc.

Square or Rectangle Length times Width Circle 3.14 x Radius x Radius (1t R2)Circumference = 3.14 x the Diameter (1tD) Right Triangle Length x Height divided by 2 Ellipse 1t X major radius x minor radius

In order to apply the information we have now determined, we need to know some other useful information:

  • Materials
  • One cubic foot of water (or any liquid) is 7.5 gallons
  • One gallon of water weighs 8.3 pounds
  • One cubic foot of Crushed stone weighs approximately 100 pounds
  • One cubic foot of sand weighs approximately 100 pounds
  • One ton of crushed stone is approximately 20 cubic feet.
  • One cubic foot of iron or steel is approximately 475 pounds.
  • One cubic foot of lumber (fir, spruce, pine) weighs from 25 to 40 Ibs per cubic ft. depending on species and moisture content.
  • One board foot is 0.833 cubic feet, or 1 square foot 1 inch thick.
  • One cubic foot of crushed limestone weighs 90 pounds.
  • One cubic foot of fertilizer weighs 60 pounds
  • Concrete
  • One Yard of-Concrete weighs 4000 Ibs wet.
  • One Yard of Concrete is 27 cubic feet
  • One Yard of Concrete is 54 60lb bags of concrete mix.
  • One Yard of Concrete is 81 square feet at 4 inch thickness.
  • Standard formula for concrete is 3 parts stone, 2 parts sand, 1 part portland cement.
  • Propane
  • One gallon of propane weighs 4.25 pounds. A 20lb cylinder holds 4.71 gallons of propane.
  • One gallon of propane contains approximately. 91,000 BTU.
  • Propane tank size is dependent on the maximum BTU draw and the lowest ambient temperature that the tank is subjected to. For example, the maximum draw on a 20lb tank at O0F would be 28,000, while at 400 you could draw 49,000 BTU.
  • Heaters
  • To determine the size space heater that you need: calculate the cubic area to be heated. (LxWxH) Multiply the desired rise in temperature by 0.133. Now, multiply the volume of the space to be heated by that. (Volume x tem- perature rise x 0.133). The result will be the BTU output of the required heater.