Rule of Thumb Estimating Costs

You can enter simple rule of thumb prices into the BidMagic construction estimating software.

Figuring Costs from a 'Rule of Thumb'

In some cases, you may have a 'rule of thumb' cost--for example, 'two bucks a square foot for concrete sidewalk.' To convert a rule of thumb to a unit price number, follow these steps:

1. Figure the materials that are used in one unit, and calculate a material unit cost. EXAMPLE: For 4" concrete, one cubic yard will cover about 80 square feet. If you pay $60 per cubic yard, that's about $.75 per square foot. With waste, reinforcing mesh and some forming materials, the total material cost will be about $.90.
2. Subtract the material cost from the overall 'rule of thumb' cost to get the cost of labor. EXAMPLE: Subtracting .90 from 2.00 leaves $1.10 per square foot for labor.
3. Use labor data or guesswork to divide the labor cost between skilled and unskilled workers. EXAMPLE: You might figure $.40 for skilled labor and $.70 for unskilled labor, per square foot.
4. Compute the net cost per hour for skilled and unskilled labor (see page 143). EXAMPLE: You may find that you pay $18 an hour for skilled labor and $10 an hour for unskilled labor.
5. Divide the number in step 3 by the number in step 4 to arrive at an hour per square foot figure for each labor class. EXAMPLE: Skilled hours per square foot will be .40/18, which equals .0222. Unskilled hours per square foot will be .70/10, or .07.
6. Enter the calculated costs into the Unit Price Editor. To double-check the accuracy of your figures, click the Show Cost button at lower left.