A new mobile app launched on May 2 by the toolmaker DeWalt lets contractors and tradespeople perform hundreds of calculations in the field, with instant feedback to show how the calculation was performed.

The free DeWalt Mobile Pro app for the iPhone, iPod or iPad has five basic calculations as well as the option of adding "packs" for hundreds of trade-specific calculations and reference materials at various costs.

The basic app includes a construction calculator for solving complex jobsite math, such as estimating the quantity of brick-mortar ties, the sand and cement needed for a structure with multiple walls, and gables and sloped elevations, says Greg Clayton, vice president of Delmar Cengage Learning, one of the app's co-creators with DeWalt. The app also shows a running history of recent calculations and has a customizable list of favorite calculations. The results can be e-mailed.

Mobile Pro is distinguished from other construction apps by the add-on packs, Clayton claims. Packs for plumbing, electrical, HVAC, landscaping and finished materials will be released in the next three months, but five packs are out now at costs ranging from $2 to $10; they include carpentry, concrete, business and finance, sitework and construction math, which has numerous templates for calculations.

Bobby Person, Delmar executive editor, says the templates cut "the danger of errors" by reducing data entry, since formulas and other data embedded in the system are accessible via a pull-down menu, with options such as stairs, wall openings or roof underlayment.

Ben McKenzie, owner of McKenzie Property Management, Charleston, S.C., says the app is especially handy for area and volume conversion when calculating materials. "When you put in new drywall, it lets you choose the gypsum board size and calculates the total number of sheets for the room area," he says. "It's not always exact, since you sometimes have oddball cuts and pieces, but it gets you in the ballpark so you can start rolling without exact drawings."