How to Calculate Cut and Fill From a Grading Plan (No CAD Required)

Earthwork is where sitework bids are won and buried. Cut is the dirt you remove where existing grade sits above the design; fill is what you place where it sits below. The difference — net import or export — decides whether you're hauling trucks in or out, and at real haul rates, being wrong by a few hundred yards is real money.

The frustrating part: the information is right there on the grading plan, drawn as contours. The math has just been locked behind CAD software or outsourced takeoff services. Here's how it actually works — and the fast way to do it yourself.

The concept in one paragraph

A grading plan shows two ground surfaces on the same sheet: existing contours (usually dashed) and proposed/finished contours (usually solid), each line marking a constant elevation. Build a 3D surface from each set, subtract one from the other over the site, and every spot where existing sits higher than proposed contributes cut; everywhere lower contributes fill. Integrate over the area and you have cut CY, fill CY, and net.

The units trap: bank vs. loose vs. compacted yards

Before any method, get the units straight — this is the classic earthwork mistake:

• Bank yards (BCY): dirt measured in the ground. This is what cut/fill math produces.
• Loose yards (LCY): dirt in the truck. Soil swells when excavated — commonly ~25% for ordinary earth — so 1,000 BCY of cut is ~1,250 LCY of hauling.
• Compacted yards (CCY): dirt after placement and compaction — soil shrinks below bank volume when compacted (factor from the geotech report).

Bid hauling on loose yards, fill on compacted yards, and label which one every number is. Estimates that just say "yards" are how disputes start.

Method 1: Grid method by hand

Lay a grid over the plan (say 50′ squares), read existing and proposed elevation at each node, average the difference per cell, multiply by cell area, divide by 27. It works — it's also hours of squinting and transcription, and accuracy depends on grid density exactly where the site is most complicated.

Method 2: CAD/civil software

Civil 3D, AGTEK, Trimble Business Center: build both surfaces properly and get excellent volumes — if you have the CAD files (bid sets usually give you PDFs), the software seats, and the operator. For many contractors this becomes "send it out to a takeoff service and wait days for the answer."

Method 3: Trace the contours on the PDF

This is what our Cut/Fill tool does, and the workflow mirrors how the plan was drawn in the first place:

1. Set the sheet scale (engineering scales like 1″ = 20′ included).
2. Trace the existing contours — click along each dashed line and type its elevation once; the tool auto-steps by your contour interval as you move to the next line.
3. Trace the proposed contours the same way, and drop spot grades for point elevations — finished floor, pad corners, top of wall.
4. Compute. The tool builds both surfaces from your traced lines, differences them, and returns cut CY, fill CY, and net import/export — with a color heat map on the sheet showing exactly where the dirt moves.
5. Send to takeoff so the volumes become line items your estimate can price, with swell factors applied for the truck-yard math.

Accuracy tracks the contour interval on the plan — the same limit any surface-from-contours method has, including the preliminary numbers engineers publish. The heat map is your audit: if the red and blue land where the grading narrative says they should, the volume is defensible.

Sanity checks before you bid it

• Compare your net to the engineer's earthwork note if the plan has one — you're validating reading, not copying answers.
• Check the balance point. A site designed to balance (net ≈ 0) that computes 2,000 CY of export means a tracing error — or a real problem worth an RFI.
• Confirm stripping/topsoil handling. Cut/fill from contours doesn't know about the 6″ of topsoil that gets stripped and stockpiled; carry it separately.
• Read the geotech. Shrink/swell factors and unsuitable-material notes change the truck count more than the surface math does.

Do the next one in minutes

If you've been paying an earthwork service $300–$800 a pop and waiting days, or passing on sitework bids because the CAD workflow wasn't worth it: trace the contours yourself and have the volumes this afternoon. Try it free — no CAD files, no charge today.