Figuring Construction Unit Costs

This section explains how to calculate construction unit prices for the BidMagic construction estimating software.

Figuring Unit Prices Directly

In many cases, you'll be able to figure unit prices directly, by calculating the number of actual person-hours it takes per unit, and the material cost per unit.

EXAMPLE: if you know it takes a crew of two skilled carpenters 1 hour and 20 minutes to hang an exterior door, then the skilled labor cost will be approximately 2 * 1.33 hours, or 2.66 person-hours per door. If each door costs $235 and requires $55 of additional hardware, then the material unit cost will be $290 per door.

If your crews fill out detailed time cards, then you'll be able to use them directly to calculate unit prices for work that you've done in the past.

NOTE: This is the most accurate way to arrive at unit labor costs, since it's based on actual paid hours.

You can also try the stop-watch approach, or use an intuitive 'feel' for how long something should take. In such cases, it's a good idea to adjust the times upwards by 10-25% to account for setup time, material deliveries, breaks, and other unproductive hours.

When calculating material costs, figure in a 'waste factor' to account for ordinary losses during construction.

NOTE: For even more accuracy, you can use MacNail Customizing to build material assemblies to calculate material unit prices (see page 382).

Figuring Unit Prices from Units-per-Time

For labor costs it is sometimes easier to start with the number of units that can be done by a crew in an hour, day or week. To convert that to a number you can use in Specifications, use these formulas:

skilled hrs/unit = skilled crew size * hours / total number of units

unskilled hrs/unit = unskilled crew size * hours / total number of units

EXAMPLE: if a crew of three skilled carpenters and one unskilled helper can install 25 pre-hung doors in a day, the skilled unit cost will be equal to 3*8/25, or .96 hours per door, and the unskilled unit cost will be equal to 1*8/25, or .32 hours per door.