Landscape material estimating comes down to one formula: area times depth equals volume. But the practical details — compaction factors, minimum delivery quantities, material weight, and the difference between nominal and settled depth — are where most homeowners and contractors get caught short or over-order.
This guide covers the real-world math for mulch, topsoil, gravel, and decorative stone. It explains why your 3-inch mulch layer settles to 2 inches, why gravel compacts by 10–15%, and at what quantity bulk delivery beats hauling bags from the home center. If you have used the Mulch & Gravel Calculator to get your number, this guide explains the reasoning behind it.
Volume Calculation Fundamentals
Every landscape material calculation starts with the same formula:
Cubic yards = (Length ft × Width ft × Depth inches) ÷ 324
The 324 factor converts square feet × inches into cubic yards (27 cubic feet per yard × 12 inches per foot = 324). This is the formula on every landscape supply calculator, and it works for any rectangular area.
For irregular areas, break the shape into rectangles and triangles, calculate each separately, and add them. For curved beds, approximate with rectangles — being off by 5% on a curve matters less than being off by 50% on depth.
Common depth benchmarks:
- Mulch (weed suppression): 3–4 inches. Less than 3 inches allows sunlight through and weeds grow. More than 4 inches can hold excess moisture against plant stems and cause rot.
- Mulch (aesthetic only): 2 inches. Freshens up existing mulch beds.
- Topsoil (lawn repair): 2–4 inches. Enough to level low spots and provide a seed bed.
- Topsoil (new garden bed): 6–8 inches. Deep enough for root development in vegetable gardens and perennial beds.
- Gravel (walkway): 2–3 inches over compacted base.
- Gravel (driveway base): 4–6 inches of compactable crushed stone, then 2 inches of surface gravel.
Cubic yards = (L × W × D) ÷ 324
Where L and W are in feet, D is in inches.
Example: 20 ft × 4 ft bed at 3 inches deep = 240 ÷ 324 = 0.74 cubic yards. Round up to 1 yard for the order.
Mulch, Topsoil & Gravel Calculator
Calculate cubic yards, bags, and truck loads for mulch, topsoil, gravel, sand, and decorative stone. Includes compaction factors, weight estimates, and bulk vs bag cost comparison.
Compaction and Settling Factors
The volume you order is not the volume you end up with after the material settles. Every bulk material compacts or settles over time, and the amount varies significantly:
Mulch
Shredded hardwood mulch settles 10–20% in the first year as it decomposes and compacts from rain and foot traffic. A 3-inch layer applied in spring will be 2.4–2.7 inches by fall. Plan on topping off annually with 1 inch to maintain a 3-inch depth. Rubber mulch and stone mulch do not decompose, so they maintain depth longer.
Topsoil
Screened topsoil settles 5–10% as air pockets collapse and the soil compacts from watering. If you need 6 inches of finished topsoil depth, order enough for 6.5–7 inches. Lightly rake and water to settle before planting.
Gravel and Crushed Stone
Crushed stone (#57, #67, crusher run) compacts 10–15% when mechanically compacted with a plate compactor. A 6-inch loose layer compacts to about 5.1–5.4 inches. This compaction is desirable — it creates a stable base. Order for the loose (pre-compaction) depth, not the finished depth.
Round gravel (pea gravel, river rock) does not compact well because the round shapes do not interlock. It stays close to the installed depth but shifts underfoot. Not suitable as a structural base.
Sand
Concrete sand and masonry sand compact 5–10%. Playground sand and beach sand compact very little because the grains are already well-sorted and round.
Compaction factors mean you should order MORE material than the finished volume calculation suggests. For mulch, add 15%. For gravel that will be compacted, add 12%. For topsoil, add 8%. These factors are built into the calculator automatically.
Bulk Delivery vs Bagged: The Breakeven Point
Bagged material from the home center is convenient for small jobs but extremely expensive per cubic yard compared to bulk delivery. The breakeven point depends on your local market, but general guidelines:
Bagged Material Cost
- Mulch: $4–$6 per 2 cu ft bag = $54–$81 per cubic yard (27 cu ft ÷ 2 cu ft × bag price)
- Topsoil: $3–$5 per 40 lb bag. A cubic yard of topsoil weighs about 2,000 lbs = 50 bags × $3–$5 = $150–$250 per cubic yard
- Gravel: $5–$8 per 50 lb bag. A cubic yard of gravel weighs about 2,800 lbs = 56 bags × $5–$8 = $280–$448 per cubic yard
Bulk Delivery Cost
- Mulch: $25–$45 per cubic yard + $50–$100 delivery fee
- Topsoil: $20–$40 per cubic yard + delivery
- Gravel: $30–$60 per cubic yard + delivery
Breakeven
For mulch, bulk beats bags at about 2–3 cubic yards (the delivery fee is offset by the per-yard savings). For topsoil and gravel, bulk wins at just 1–2 cubic yards because the per-yard price difference is so large. If you need more than 2 yards of anything, always order bulk.
The exception is when you cannot get a delivery truck to the work area. If the dump truck can only reach the driveway and you need to wheelbarrow material 200 feet to the backyard, the labor cost of moving bulk material may tilt the math back toward bags that you can carry directly to the bed.
Many landscape supply yards offer pick-up pricing (no delivery fee) if you have a truck or trailer. A half-ton pickup can carry about 1 cubic yard of mulch (by volume — the bed fills up) or half a cubic yard of gravel (by weight — more would exceed the payload rating). Check your truck's payload capacity before loading gravel or topsoil.
Delivery Planning and Site Prep
Bulk delivery sounds simple until a 10-wheel dump truck is idling in your driveway and the driver asks where to dump. Plan ahead:
Access
A standard dump truck is 8 feet wide and 30 feet long. It needs a firm, level surface to dump — not soft lawn, not a steep incline. Most deliveries go on driveways. If you want the load dumped closer to the work area (backyard, side yard), verify the truck can physically reach it without driving over septic tanks, irrigation lines, or soft ground.
Dump Spot
Lay a tarp where the material will be dumped if it is on a surface you want to protect (concrete driveway, pavers). Mulch stains concrete. Gravel is nearly impossible to sweep completely off a paved surface. A 10×12 tarp costs $15 and saves an hour of cleanup.
Minimum Order
Most landscape supply yards have a delivery minimum of 2–5 cubic yards. Delivery fees are typically flat rate ($50–$100) regardless of quantity up to a full truck (10–15 yards). Order as close to the truck maximum as practical to minimize per-yard delivery cost.
Timing
Schedule delivery for the day you plan to spread the material, or the day before at most. A pile of mulch on your driveway for a week annoys neighbors and blocks parking. Gravel piles are a tripping hazard and can damage tires if kicked onto the road.
Know what is underground before dropping a 4-ton pile of gravel on your lawn. Septic drain fields, irrigation lines, and buried utilities can be damaged by heavy truck traffic. Call 811 (utility locates) before scheduling delivery if the truck will drive off paved surfaces.
Choosing the Right Material
Not all mulch is the same, and the wrong gravel for the application causes problems:
Mulch Types
- Shredded hardwood: The standard. Decomposes in 1–2 years, enriching soil. Holds well on slopes. Dark brown color fades to gray. $25–$35/yd.
- Double-shredded hardwood: Finer texture, knits together better on slopes, decomposes faster. $30–$40/yd.
- Pine bark nuggets: Decorative, slow to decompose, but floats in heavy rain and washes off slopes. Not for beds near downspouts.
- Cedar mulch: Natural insect deterrent (somewhat), pleasant smell, more expensive ($40–$55/yd). Acidifies soil slightly — good for azaleas, blueberries, not ideal for vegetable gardens.
- Rubber mulch: Made from recycled tires. Does not decompose, never needs replacement. Does not enrich soil, gets hot in sun, and some studies raise concerns about chemical leaching. Best for playgrounds where fall protection depth matters.
Gravel and Stone
- Crusher run (#21A): Angular crushed stone with fines. Compacts into a solid base. The standard for driveways, parking pads, and under patios. $25–$40/yd.
- #57 stone: 3/4-inch clean gravel. Drains well. Used for French drains, behind retaining walls, and as a surface layer over compacted base. $30–$45/yd.
- Pea gravel: Round, 3/8-inch. Decorative pathways, dog runs, between pavers. Shifts underfoot and migrates — needs edging to contain it. $35–$50/yd.
- River rock: Larger decorative stone, 1–3 inches. Dry creek beds, decorative borders, erosion control. Heavy and expensive ($50–$80/yd).
For driveways and parking areas, always use angular crushed stone (crusher run), never round gravel. Angular stone interlocks when compacted and stays put. Round stone shifts under tire weight and creates ruts. This is the most common gravel mistake homeowners make.
Material Weight and Hauling Limits
Volume is how you order, but weight is what determines whether your truck can haul it:
| Material | Weight per Cubic Yard | Half-Ton Truck Limit |
|---|---|---|
| Shredded mulch | 400–800 lbs | 1.5–2 yards (by volume, bed fills first) |
| Screened topsoil | 1,800–2,200 lbs | 0.5–0.75 yards |
| Sand | 2,400–2,800 lbs | 0.5 yards max |
| Gravel / crushed stone | 2,600–3,000 lbs | 0.5 yards max |
| River rock | 2,400–2,800 lbs | 0.5 yards max |
A half-ton pickup (F-150, Silverado 1500, Ram 1500) typically has a payload capacity of 1,200–2,000 lbs depending on configuration. That limits you to about half a cubic yard of gravel or topsoil. Exceeding payload capacity damages suspension, brakes, and frame — and voids your warranty.
A 3/4-ton truck (F-250, 2500 series) handles 2,500–3,500 lbs, allowing about 1 yard of heavy material. For larger quantities, bulk delivery is the only safe and practical option.
One cubic yard of wet topsoil can weigh over 2,500 lbs — enough to exceed the payload of most half-ton trucks. Always check your vehicle's payload rating on the driver's door sticker before loading heavy materials. An overloaded truck handles poorly, brakes poorly, and can fail catastrophically.
Frequently Asked Questions
At 3 inches deep (the standard for weed suppression): 1,000 × 3 ÷ 324 = 9.3 cubic yards. Round up to 10 yards to account for settling and uneven spreading. At 2 inches deep (topping off): about 6.2 cubic yards.
Most bagged mulch is sold in 2 cubic foot bags. One cubic yard = 27 cubic feet ÷ 2 = 13.5 bags. So 14 bags equals roughly 1 cubic yard. At $4–$6 per bag, that is $56–$84 per yard in bags vs $25–$45 per yard bulk. Bags only make sense for very small jobs under 2 yards.
2–3 inches of surface gravel over a compacted base layer. For a proper walkway, excavate 4–6 inches, lay landscape fabric, add 2–4 inches of compactable crusher run as a base, compact it, then add 1–2 inches of decorative surface gravel. Total gravel depth: 4–6 inches including base.
Mulch does not attract termites, but termites already in the soil may travel through mulch to reach your foundation. Keep mulch 6 inches away from the foundation, below the siding line. Cedar and cypress mulch have mild natural resistance to insects but are not termite-proof. Do not stack mulch against wood siding.
Crushed stone and gravel weigh approximately 2,600–3,000 lbs (1.3–1.5 tons) per cubic yard. Pea gravel is slightly lighter at 2,400–2,600 lbs. River rock varies by size but averages 2,400–2,800 lbs per yard. These weights are for dry material — wet material is 10–15% heavier.
Yes, if the old mulch has decomposed and the total depth stays at 3–4 inches. If the old mulch is still 2+ inches deep and you add 3 more inches on top, the 5-inch total can hold too much moisture and suffocate plant roots. Rake out excess old mulch before adding new if the bed is already deep.
Crushed stone and gravel are the cheapest per square foot for permanent ground cover ($0.50–$1.50/sq ft at 2-inch depth). Mulch is cheaper initially ($0.25–$0.75/sq ft) but decomposes and needs annual replacement. Over 5 years, stone is usually cheaper than mulch because it does not need replacing.