How to Estimate Earthwork Materials: Step by Step Guide

Estimating earthwork materials means turning the site plan and the cut and fill numbers from your takeoff into a buy list of fill, aggregate base, fabric, and hauling, each in its own unit and each with its own swell or compaction factor. Earthwork is a mass of dirt, not a sheet good, so the takeoff starts with volume and then converts between in place, loose, and compacted states before anything gets priced.

What You Are Counting

An earthwork material takeoff is five groups of materials stacked together. You count and measure the fill material itself (common fill, select fill, structural fill), the crushed aggregate base, the geotextile separation fabric, the compaction tests, and the hauling and disposal. Each group has its own unit and its own logic, and you price them as separate line items because the suppliers and the testing lab quote them separately.

Fill is bought by the cubic yard (CY) in place, but hauled by the loose CY in the truck, and compacted by the bank CY in the field. A swell factor of 1.2 converts bank to loose, and a compaction factor of 0.85 to 0.9 converts loose to compacted. Aggregate base is bought by the CY or by the ton, with 1.4 tons per CY as a rule of thumb. Geotextile is bought by the SY of coverage, in rolls. Compaction tests are bought by the each, one per 250 CY of fill or per lift. Hauling is bought by the truckload, by the ton mile, or by the CY hauled.

Units and Waste Factors

Earthwork waste factors are really shrink and swell factors, and they are larger than for any other trade. Common fill runs 10 to 15 percent shrink from loose to compacted, which means you need 1.1 to 1.15 loose CY to make 1.0 compacted CY. Select fill and structural fill run 15 to 20 percent shrink because they are placed and compacted to a Proctor. Aggregate base runs 5 to 10 percent compaction. Geotextile runs 10 percent for lap and waste at the edges.

The rule of thumb is to compute the fill volume in place, then divide by the compaction factor to get the loose volume you need to buy. Round the loose volume up to the truckload. A 10 CY truck that runs 5 times delivers 50 CY, so an order of 47 CY becomes 50 CY. Hauling is priced on the rounded number, not the theoretical one.

Step by Step Material Takeoff

Work the takeoff in the same order the site gets graded, from the existing grade to the proposed grade.

• Step 1, pull the site plan and the grading plan. Note the existing and proposed contours. Identify the limits of grading, the building footprint, the parking area, the access road, and any stockpile areas.
• Step 2, compute the cut and fill volumes. Use cross sections or a grid takeoff. For each grid cell, multiply the average cut or fill depth by the area. Sum the cut CY and the fill CY separately. The difference is what you haul on or haul off.
• Step 3, balance the site. Compare cut to fill. If cut exceeds fill, the excess is haul off. If fill exceeds cut, the shortage is import. Apply the swell factor to the haul off (bank to loose) and the compaction factor to the import (loose to compacted) to get the buy volume.
• Step 4, take off the aggregate base. Measure the area to be based in SF, multiply by the base thickness in feet, divide by 27 to get CY. Add 5 percent compaction. Convert to tons at 1.4 tons per CY for pricing.
• Step 5, take off the geotextile. Measure the area to be covered in SF, divide by 9 to get SY. Add 10 percent for lap. Round up to the roll size.
• Step 6, count the compaction tests. One Proctor test per fill type, one density test per 250 CY of fill or per lift, whichever is less. Count the tests by the each.
• Step 7, apply waste factors and round up. Add the shrink and swell factor to each line item, then round up to the buy unit. Sum the priced quantities by spec division (31 00 00 earthwork, 31 23 00 excavation and fill, 32 11 00 aggregate base).

Where Estimators Miss

The most common miss is computing fill volume without the compaction factor. A takeoff that says 500 CY of fill and orders 500 CY of loose fill will come up 50 to 75 CY short once the fill is compacted to a Proctor. Divide the compacted volume by the compaction factor to get the loose volume to buy.

The second miss is forgetting the swell on haul off. A 200 CY cut does not fit in 200 CY of truck. It swells to 240 loose CY, and that is what you pay to haul. Apply the swell factor to the cut before pricing the hauling.

The third miss is undercounting the compaction tests. The testing lab charges by the test, and a large fill with one test per 250 CY can run 20 or 30 tests. List them in the takeoff because they are a real line item and they get missed.

The fourth miss is mixing up the area to be based. A parking lot measured on plan at 10,000 SF and based at 8 in takes 247 CY of base, not 100 CY. The thickness is what drives the volume, and forgetting it underprices the base by a factor of two or three.

Worked Example

For a representative earthwork scope, a 1 acre site with 500 CY of cut and 300 CY of fill: the cut exceeds the fill by 200 CY, which swells to 240 loose CY hauled off. The fill of 300 CY compacted requires 350 loose CY imported at a 0.85 compaction factor. The aggregate base for a 5,000 SF parking area at 6 in takes 92 CY, or 130 tons at 1.4 tons per CY. The geotextile under the parking area runs 5,000 SF plus 10 percent lap, or 611 SY. A typical direct cost breakdown for this scope is:

Numbers are illustrative and vary by region, project size, and material choice. Use them as a sanity check, not a bid.

Putting It Together

An earthwork material takeoff is built from cut and fill volumes, balanced with swell and compaction factors, matched to aggregate base and geotextile, and rounded up to the truckload. Pad each line item with the right shrink or swell factor and round up to the buy unit. Price by spec division, total it, and the buy list is the bid. Get the volume and the factors right and the site balances on the first round of hauling.