Most contractors use a mix of techniques to arrive at their estimates. Many use some combination of stick estimating and unit-cost estimating, with a little human judgement to help them make final adjustments for conditions that may affect the cost of construction (almost always in the upward direction). Except for very small or simple estimates done with paper and pencil, most contractors use estimating software to help with the project — most often a spreadsheet to help keep simplify the task and make easy revisions as prices change or work is added or subtracted from the estimate. But whether they are using a pencil and paper or the most sophisticated software program, the process is essentially the same: they are either adding up costs stick-by-stick, or plugging in unit costs that they either got from a book or (much better) developed themselves based on experience.
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