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After entering the counts, material cost, and the labor-hour value for each item, you must check the totals for each worksheet page. Look for any individual numbers that look unusual and check them against the plans or calculate them manually to double check your spreadsheet formula. If you’re using estimating software, perform the same checks to make sure none of the item assemblies contained an incorrect material item or labor amount.

Material Cost Extension
To determine (or calculate) the material cost extension for each item, divide the material cost by the unit, then multiply that value by the quantity of material items. If you're using a spreadsheet, make sure to enter individual units quantities instead of (C) or (M) so that you can use the same formula to extend each total.

Example: The total cost of 26 metal boxes that cost $53.70 per 100 (C) boxes is: $53.70/100 x 26 boxes = $13.96.

Labor-Hour Extension
Calculate the labor-hour extension for each item by dividing the labor hours by the unit, then multiplying that value by the quantity of the material items. If you're using a spreadsheet, make sure to enter labor individual units instead of (C) or (M) so that you can use the same formula to extend each total.

Example: The total labor to install 26 metal boxes at 18 hours per 100 (C) boxes is: 18.00/100 x 26 boxes = 4.68 hours.

Important: Have someone else double-check your extensions and totals for each page so you gain confidence that your material cost and labor hours are probably correct. Be certain to double-check owner-supplied equipment and/or material for accurate counts and use your own labor units for pricing.

Historical Data
It's no secret that an estimator's best friend is historical data and what makes this data most effective is accurate record keeping. As your business grows and you complete and reconcile more and more jobs, those file folders that you've been keeping for each job estimate, establish a track record of your costs, profits, and/or losses for each job. This working job history is an invaluable resource when estimating new work that is similar to work that you've already done. You can look back on this data to see what it took to complete a particular job (or aspect of a job) and make any adjustments deemed necessary to labor units or material assemblies to ensure a more accurate bid.

The above content is extracted from Mike Holt's Electrical Estimating Program.