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The Dirt Calculator Guide Library

Dirt Guides That End at a Number You Can Use

A library of practical earthwork guides organized into four shelves — volume & geometry, materials & density, compaction & coverage, and cost & logistics. Written to be read with the dirt calculator open in the other tab: the reading explains why a number moves; the tool shows how far it moves.

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Open notebook with yard measurements beside a pile of screened topsoilRead it here, run it therePhoto: Unsplash
About This Library

What the Dirt Guides Cover, and Why

Ask a dirt question online and you get folklore: “a yard covers a parking space,” “fill is fill,” “order extra to be safe.” Some of that advice is right for some projects — and expensive or short for others. The gap between the two is exactly what this library exists to close, and it closes it the same way every time: with the actual arithmetic, the actual density data, and the actual shrinkage behind the number.

Every guide follows one design rule: it must end at a number you can enter somewhere. Volume guides connect to the shape modes and dimension inputs. Density guides connect to the material selector and the tonnage output. Compaction guides connect to the buffer slider. Cost guides connect to the $/yd³ field, the bag-size dropdown, and the ZIP input. If a concept cannot change a number you can type, it does not get a page here — there are enough dirt essays on the internet already.

The library is organized into four shelves, and the shelves are not cosmetic. They are the four questions every dirt order actually asks, in the order the work asks them: how much space the project fills, what the material weighs, how far a yard spreads, and what the whole thing costs delivered. A reader who works through all four shelves ends up with a complete, checkable picture — and, more importantly, with the ability to see exactly which assumption is carrying the number when a quote disagrees with a calculation.

Guides publish here as they are finished. The first three on the workbench — fill dirt vs. topsoil, compaction shrinkage, and the bags-vs-bulk breakeven — are outlined below, and every topic card in the shelves already states the takeaway it will deliver. While the library is written, the homepage method covers the practical calculation, so nothing here is a teaser for information you cannot use today.

Worker spreading fill dirt with a rake across a regraded yardWritten for the pilePhoto: Unsplash

How the guides are built

Each guide is drafted against a real question from the calculator’s audience, checked line by line against the source it cites, and paired with the exact input fields where its conclusion changes a number. Nothing publishes because a keyword needed a page.

The Four Shelves

The Library, Sorted by the Question You Brought

Sixteen planned guides across four shelves. Each topic card below states the takeaway you should walk away with — and every takeaway ends at an input the calculator accepts or an output it displays. Drafted guides publish at the top of this page; the shelves grow as they land.

Shelf 01 · Volume & Geometry

How much space, in which shape

Every decision downstream — material, trucks, cost — is hostage to one number: the cubic yards the project actually needs. These guides cover the chain from tape measure to volume: which formula each shape uses, why depth is the dimension everyone under-measures, and how multi-zone projects should be summed.

  • The ÷27 rule, and where it comes from

    A cubic yard is 27 cubic feet — three feet on a side — so every length × width × depth in feet divides by 27 to land in the unit suppliers quote. The guide derives it, works it at common bed sizes, and shows why measuring depth in inches without converting is the number-one volume error.

  • Depth: the dimension that decides everything

    Doubling the depth doubles the order — and 'a few inches' is where estimates quietly die. The guide sets realistic depths by use case: 2–4 inches for topdressing a lawn, 6–12 for a raised bed, 4–6 compacted for a driveway base, and how to probe an existing grade before guessing.

  • Circles, rings, and triangles without tears

    Round beds use πr² × depth; a ring subtracts the inner circle from the outer; a triangle halves the bounding rectangle. The guide works each formula on a real example — a 10-ft tree ring, a corner bed — so the calculator's shape modes are checkable by hand.

  • Slopes, wedges, and trapezoid sections

    A tapering slope is half its bounding box; a driveway section is (top width + base width) ÷ 2 × depth × length. The guide explains when the wedge assumption holds, when to split a complex slope into zones, and how the road mode matches the way contractors actually measure.

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Shelf 02 · Materials & Density

What a yard of it actually weighs

A cubic yard of compost weighs about a ton; a cubic yard of clay-heavy fill approaches 1.75. Density is what turns a volume into a truck count and a weight limit — and it is the input generic calculators get wrong by treating all dirt alike. These guides compare the materials with the numbers kept honest.

  • Fill dirt: mixed, screened, sandy, clay

    Mixed unscreened fill is the cheapest grade-up material; screened trades cost for cleanliness; sandy fill drains and compacts least; clay compacts hardest and shrinks most. The guide compares all four on price, density, and the jobs each one is actually for.

  • Topsoil: what 'screened' buys you

    Screening removes rocks, roots, and clods — and roughly doubles the price. The guide explains when unscreened topsoil is fine (large lawn areas, rough grading) and when the screened premium pays for itself (seed beds, topdressing, anywhere a rake will touch).

  • Sand, compost, and specialty blends

    Fill sand beds pipes and pavers; compost mix feeds beds but never bears load; engineered fill carries a spec and a price to match. The guide covers the specialty materials' densities and the failure modes of using the cheap one where the spec one belongs.

  • Moisture: why today's yard weighs more than yesterday's

    The same pile of dirt gains hundreds of pounds per yard after rain — which is why suppliers price by volume and quarries by weight, and why the two invoices never quite match. The guide explains loose vs. compacted vs. wet volume so the units on the quote stop surprising you.

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Shelf 03 · Compaction & Coverage

How far a yard really goes

Delivered dirt is loose; finished dirt is compacted; and the gap between them is where under-orders are born. These guides cover shrinkage by soil type, the coverage-per-yard table at every common depth, and the spreading logistics that decide whether one delivery finishes the job.

  • Shrinkage factors by soil type

    Sandy fill shrinks about 10%, general residential fill 15%, clay-heavy fill 20–25%. The guide shows where each preset in the calculator's buffer slider comes from — and the mechanical-compaction cases that exceed every preset.

  • Coverage per yard: the 1"–12" table

    One cubic yard covers 324 sq ft at one inch deep, 108 at three inches, 27 at a foot. The guide reproduces the full coverage chart, shows how to use it backwards (area first, depth second, yards third), and why it is the fastest audit of any supplier's estimate.

  • Lifts: why deep fill is placed in layers

    Fill deeper than about 8 inches compacts properly only in lifts — thin layers, each compacted before the next. The guide explains the practice, what it does to the schedule, and why a 'one big pile, one big pass' job settles for years.

  • Settling vs. compaction

    An uncompacted lawn regrade will settle on its own — over months, unevenly, and usually after the sod is down. The guide separates deliberate compaction from passive settling so the buffer percentage matches the placement method, not the hope.

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Shelf 04 · Cost & Logistics

Getting it to the curb on budget

The material is often the cheap part. Delivery fees, minimum loads, truck sizes, and the bags-vs-bulk decision decide the real budget — and they are the line items first-time buyers never see coming. These guides price the whole chain, not just the dirt.

  • What a yard of fill dirt costs in 2026

    Mixed fill runs $5–$15 per yard material-only, screened topsoil $20–$40, compost blends $25–$50 — before the truck. The guide lays out the price bands by material and region, and the questions that move a quote inside its band.

  • Delivery fees, zones, and minimum loads

    Most yards charge by zone or mile, many waive the fee above a load threshold, and all of them price a partial truck like a full one. The guide explains how the calculator's ZIP-based range is built — and how to structure the order so the truck works for its fee.

  • Truck sizes: pickup to tri-axle

    A half-ton pickup carries about 2.5 yards heaped (and is over its weight rating with heavy fill); a single-axle dump takes 10, a tandem 14, a tri-axle 16. The guide matches truck capacity to order size so the trip count is known before the scheduling call.

  • Site access: where the pile can land

    The truck dumps where it can reach — and a pile on the wrong side of the fence is a wheelbarrow weekend. The guide covers drop placement, driveway weight limits, overhead lines, and the access cases where bags or a conveyor truck beat a dump.

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Homeowner and supplier reviewing a dirt delivery plan beside a dump truckThree paths through the same libraryPhoto: Unsplash

The one editorial rule

No guide may state a number it cannot trace — to the ÷27 volume rule, the published density ranges, the shrinkage presets, or the coverage-per-yard table. Where sources disagree, the guide says so and shows both, because a reader who can see the disagreement can resolve it against their own project.

Reading Paths

How to Read This Library

Sixteen planned guides are a lot if you read them in order and unnecessary if you read them by role. These are the three routes through the shelves that match why people arrive here — each one sequenced so the arithmetic arrives before the decisions that depend on it.

The homeowner's path

Start with the ÷27 rule and realistic depths — that is the entire arithmetic behind a quote. Finish with bags vs. bulk and delivery fees, and you can read any supplier's estimate, ask the two questions that matter, and know which line items are real.

The DIYer's path

Everything in the homeowner's path, plus the whole third shelf — shrinkage, lifts, and coverage — before the first shovel hits the pile. The guides are deliberately blunt about which shortcuts are cosmetic and which ones regrade the yard twice.

The contractor's path

Density by material and the coverage-table backwards-read are the two that change bids; the compaction guides are the ones that change callbacks. The rest of the library is the reference layer that keeps your assumptions consistent from estimate to delivery.

Guides Are in Progress

Three Guides on the Workbench

These three publish next because they answer the questions the calculator receives most. While they finish, the calculator and the homepage sections already cover the practical method — start there and the guides will catch up to you.

Coming soon

Fill Dirt vs. Topsoil: Which Layer Goes Where

Fill dirt builds grade and costs $5–$15 a yard; topsoil feeds plants and costs two to three times more — and swapping them is the most expensive ordering mistake in residential earthwork. This guide maps the two-layer system (fill below, topsoil above), the depth each layer actually needs, and the density difference that changes the tonnage on the truck.

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Coming soon

Compaction: Why Ordered Volume Is Not Placed Volume

Loose delivered fill shrinks 10–25% once it is spread and compacted — which is why the calculator's buffer slider exists and why so many first-time orders come up short. This guide walks shrinkage by soil type, lift thickness, and when a plate compactor changes the math — so the buffered number is a decision, not a default.

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Coming soon

Bags vs. Bulk: The Real Breakeven

A 1.5 cu ft bag of topsoil holds one-eighteenth of a cubic yard, so bag prices that look modest multiply fast — while bulk delivery carries a fee that punishes tiny orders. This guide works the breakeven with real per-yard and per-bag pricing, and covers the access cases where bags win at any volume.

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Meanwhile, on the Homepage

The Method Is Already Live

You do not have to wait for the guides to size an order. The homepage walks the full method — how shape drives the volume, how density turns it into weight, where the compaction presets come from, and how coverage and cost close the loop — section by section, with the calculator running beside it.

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Size Your Order Today

Open the calculator, pick a shape per zone, choose the material, and watch the yards, tons, bags, truckloads, and delivered cost line up in real time — free, no account, entirely in your browser. When a guide above sharpens an assumption, the calculator is updated to match it.

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