Run the same math on the gravel calculator for any dimensions; it surfaces the practical-order cushion, converts yards to tons by gravel type, and flags the supplier-minimum threshold where bulk stops being cheaper than bagged gravel.
How to buy it (the short version)
Once you know your practical-order yardage, the buying decision is three-way:
- Under 1 yd³ → bagged from a big-box. ~54 bags per yard at 0.5 cu ft each. Delivery fees + bulk minimums make small bulk orders cost more than the bag equivalent.
- 1-5 yd³ → compare small-yard delivery vs bags.Most quarry-direct yards won't dispatch under 5 yd³. Smaller landscape suppliers will, often with a $50-100 small-load surcharge. Run the math both ways; bags win up to ~2 yd³, bulk wins past that on most jobs.
- 5+ yd³ → bulk delivery, every time.Above the supplier minimum, bulk is dramatically cheaper per yard than bagged gravel. Confirm both yards AND tons on the dispatch ticket; the two should agree at the supplier's published density.
Most aggregate yards won't dispatch a truck under 5 yards. Skip that detail and a small job costs you a small-load fee — or two extra trips to a big-box for bagged gravel.
Ask a SiteworkMath question
Quick answers about SiteworkMath's calculators and material take-offs — concrete yardage, topsoil + mulch volume, tile box-count, deck-surface materials. Free, no signup. Not structural-engineering or code advice — for joist / beam / footing / permit decisions, talk to a structural engineer, licensed contractor, or your local building department.
Hi, I'm the SiteworkMath assistant. I answer questions about the calculators and guides on this site — concrete yardage, topsoil, mulch, tile, and decking material math. I'm not a structural engineer or a licensed contractor; I'm a calculator built around the math that James Wu — Chicago-area flipper — uses on his own jobs. For structural decisions (joist sizing, beam spans, footing depth in your soil + climate, anything that needs a permit) talk to a licensed structural engineer or your local building department.
How pros actually do this
An original asphalt driveway had cracked into plates from twenty winters of freeze-thaw. The plan was to scrape it, lay geotextile, and rebuild with 6 inches of compacted crusher run plus a 2-inch #57 top dressing. The tape said 12 feet by 40 feet — 480 square feet.
Volume math for the base: 480 × (6/12) / 27 = 8.89 cubic yards exact, or about 13.80 tons at crusher run's 115 lb/ft³ loose density. With the 7% cushion the practical order was 9.75 yards, 15.14 tons. I called the supplier with 15.5 tons loose to leave a real working cushion and hold the truck arrival to early morning, so I had all day to spread and compact.
The trap on that job had nothing to do with the volume math — it was the compaction multiplier. Crusher run loses 15-20% from loose to compacted depth1. The first time I ran a base job I ordered the design depth, compacted it, and ended up about an inch short on the finished grade. Now I order LOOSE depth = design × 1.20 every time on a compactable base. The calculator surfaces the note when crusher run is the selected type; that one note pays for the whole page.
My opinion on bulk versus bagged is the boring one: above 1 cubic yard the math says bulk, but the supplier minimum says otherwise on most jobs. A 1.5-yard surface French drain is a perfect example — the math says bulk, the 5-yard minimum says bagged at the big-box. Don't fight that math. Pay the small-load fee only when bagged becomes genuinely impractical (a job too far from a store, or material that isn't bagged at retail, like #3 ballast stone).
The four steps
1. Measure the area in feet.
Length and width go in as feet — measure the long edge of the area and the short edge. For an irregular shape (an L, a curve, a trapezoid), split into rectangles, compute each, and sum. Don't eyeball the area; gravel orders are sensitive enough to rectangle accuracy that a 10% measurement error blows the cushion.
2. Pick the spread depth.
Depth in inches, by use case: 8-12 inches total in three layers for a driveway (4-6″ compacted crusher-run subbase + #3 middle + 2″ #57 top), 2-3″ for a walkway, 12″ for a yard / surface French drain trench (the DIY scope — footing-depth foundation drains are separate waterproofing work), 2-3″ for a decorative bed. The USDA NRCS Earth and Aggregate Surfacing Design Guide1 is the anchor for the driveway range; lighter applications use supplier and landscape-extension conventions.
3. Compute cubic yards.
The formula: area in square feet × depth in feet, divided by 27. Depth converts from inches by dividing by 12. So a 12 × 40 driveway at 6 inches is 480 × (6/12) / 27 = 480 × 0.5 / 27 = 8.89 yd³. That number is the EXACT volume — what the area geometrically holds, before any cushion or rounding. Gravel is sold by the cubic yard or the ton, so the cubic-yard number is what becomes the order.
4. Add the cushion, then round to the dispatch unit.
Multiply by 1.07 for the 7% cushion: 8.89 × 1.07 = 9.51 yd³. Then round UP to the next quarter-yard the supplier honors: 9.75 yd³. Convert to tons by multiplying by density × 27 ÷ 2000 — for crusher run at 115 lb/ft³ that's 9.75 × 27 × 115 / 2000 = 15.14 tons. Call the supplier with both numbers; the dispatcher will pick the billed unit, and you want to confirm they agree on the type and quantity before the truck rolls.
Run the math yourself
Type your dimensions and pick the use case. The calculator is the same engine the math above runs on — it handles the cushion, the tons conversion, the compaction multiplier on crusher run, and the 5-yard supplier-minimum warning.
Where this number breaks down
A few traps that put the math on the wrong side of the order:
- Compaction loss on the base.Crusher run, road base, #3 stone all compact 15-20% from loose to finished depth. Order the LOOSE depth = design × 1.20. The calculator's number is loose depth — what arrives on the truck, not what stays after compaction. The 1.20 multiplier assumes you actually compact; a plate compactor passes twice over each 2-inch lift is the install standard.
- Wrong gravel type for the job. Pea gravel on a driveway gets shoved into ruts within a season; crusher run in a French drain clogs the perforated pipe because the fines pack the flow path. Match the type to the application: angular #57 for drainage, compactable crusher run for subbase, rounded pea for walkway comfort, decorative river rock for bed.
- Geotextile fabric skipped on clay. On heavy Chicago-suburb clay, NRCS Construction Specification 4952calls geotextile non-negotiable under driveways. Skip it and within three rainy seasons the soil fines migrate up into the gravel, the void space disappears, and the driveway turns into a soft strip that won't drain. The math says 9.75 yards; without fabric, two of those yards effectively vanish into the subsoil within a few years.
- Density variance by supplier.The calculator uses sane midpoint densities (96-115 lb/ft³ across types). Actual delivered density varies by blend, moisture, and gradation — a wet crusher-run load can run 125 lb/ft³ instead of 115, and your yards-to-tons ticket math won't line up cleanly. Ask the supplier for their published spec-sheet density if the order is large enough that the difference matters in dollars.
- Supplier minimum below 5 yards.A 1-yard decorative bed math-checks at 1.0 yd³ + 7% cushion = 1.25 yd³ practical. Below 5 yards most quarry-direct yards won't dispatch. Either find a smaller landscape supplier, pay a small-load surcharge, or switch to bagged from a big-box at 0.5 cu ft per bag (~54 bags per yard).
Frequently asked
How do I figure out how much gravel I need for any job?
Multiply length × width × depth (all in feet, depth converted from inches), divide by 27 to get cubic yards exact, then add a 7% cushion and round up to the next quarter-yard. For a 12 ft × 40 ft driveway at 6″ loose crusher-run base, the math is 12 × 40 × (6/12) = 240 ft³, divided by 27 = 8.89 cubic yards exact. Add the 7% cushion = 9.51, round up to 9.75 cubic yards practical. That's what you call the dispatcher with.
How deep should I spread gravel for a walkway, driveway, or French drain?
Walkway: 2-3″ of pea gravel. Driveway: 8-12″ total in three layers (4-6″ compacted crusher-run subbase, middle #3 stone, 2″ #57 top dressing) per USDA NRCS spec. Yard / surface French drain: 12″ of #57 angular clean stone in a shallow trench catching surface runoff. True below-grade foundation perimeter drains run at footing depth (3-8 ft typical) and are specialty waterproofing scope — different job, not this guide. Decorative bed: 2-3″ over a weed barrier. Compactable layers (crusher run, road base) need design depth × 1.20 in LOOSE depth ordered, because they lose 15-20% to compaction.
How much waste cushion should I add for a gravel order?
7% is the SiteworkMath default — heavier than concrete (5%) because spread spillage, corner-pack adjustments, and supplier weight tolerance all add up. Heavier still on long-haul deliveries where some weight evaporates as fines in transit. Don't double-cushion at both the yardage layer AND the compaction layer for crusher run; the 1.20 compaction multiplier covers a lot of what cushion would. Below 1 cubic yard you're rounding-error-bound to the supplier minimum anyway — cushion math stops mattering.
Should I order gravel by the cubic yard or by the ton?
Aggregate suppliers (the quarry-direct yards) bill by the ton. Landscape suppliers sometimes quote yards. Confirm BOTH numbers on the dispatch ticket — the yards-to-tons conversion runs about 1.30 tons/yd³ for pea gravel and 1.55 for crusher run loose (denser still compacted). If the supplier's per-ton price and per-yard price disagree at their own published density, ask which is the actual billed unit. Tickets that show one and invoice the other are common enough to watch for.
What's the minimum order for bulk gravel delivery?
5 cubic yards is the typical Chicago-metro residential bulk minimum at a quarry-direct yard. Smaller landscape suppliers will sometimes dispatch 2-3 yards with a $50-100 small-load surcharge tacked on. Under 1 cubic yard, bagged from a big-box is almost always cheaper once the delivery fee + minimum lands. The calculator above flags the threshold when your practical-order amount falls below 5 yards.
What I'd do next
- Run your job through the calculator
Plug in dimensions + use case, get exact yardage, tons by type, and the compaction-aware cushion.
- What a yard of gravel actually weighs
Per-type density (pea / #57 clean / crusher run / decorative) and the truck-weight math.
- How much area a ton covers
Reverse the math — when the supplier quotes by the ton instead of the yard.
Once the volume math is dialed, the next decision is usually whether to confirm the order by the yard or by the ton — most aggregate suppliers bill by the ton, and the conversion runs about 1.30-1.55 tons per cubic yard depending on type. How much is a ton of gravel covers the area-coverage math and the per-type tonnage table.
- 1. USDA NRCS TN 210-AEN-04 — Earth and Aggregate Surfacing Design Guide (August 2017) — anchor for the 8-12″ three-layer residential driveway spec and the compaction-loss range on crusher run / road base. ↩
- 2. NRCS Construction Specification 495 — Geotextile — separation-fabric requirement on heavy clay subgrades and overlap / pin specifications. ↩
By James Wu. Volume math is site arithmetic, formulas shown above. Per-type bulk densities (pea 96, #57 clean 100, crusher run 115, decorative 95 lb/ft³) are midpoints from supplier spec sheets cross-checked against Omnicalculator (105 lb/ft³ default) and InchCalculator (1.4-1.7 tons/yd³ range). Compaction-loss range and earthfill / gravel-fill construction practice from NRCS Construction Specification 423 — Earthfill and Gravel Fill. Engine logic in lib/sitework/gravel.ts. Not geotechnical or structural-engineering advice — for soil-bearing capacity, frost-line drainage, or any base prep under a structural slab, consult the local building inspector or a geotechnical engineer. Full methodology.