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Gravel Calculator

Area and depth into cubic yards and tons, using a state DOT’s published unit dry weights — and separately, the loose volume that tonnage will actually arrive as.

How are you measuring the area?
ft
ft
in

The finished depth of this layer, in place. The 4 in shown is a starting value, not a recommendation — spread depth comes from your spec, your engineer, or your supplier, and varies with traffic and subgrade.

WSDOT unit dry weights. Aggregate density is a measured, source-specific property, so a quarry in your state may publish something different — use their figure when you have it. Gravel base ranges from 1.7 t/cy where the grading is mostly sand to 1.9 t/cy where it approaches ballast.

%

Adjustable. Aggregate is sold in bulk and a second delivery costs another haul fee, so most estimators carry some overage for spread variation and an uneven subgrade. It is a buying allowance, not a spec.

Order

12.1

tons

6.52 cu yd in place

The working

Area: 40 × 12 = 480.0 sq ft

Volume: 480.0 × 4″/12 = 160.00 cu ft

160.00 ÷ 27 = 5.93 cu yd

+ 10% overage = 6.52 cu yd

× 1.85 t/cy (compacted on roadway) = 12.06 tons

Planning estimate only. Check the result against current product instructions, local requirements, and your own takeoff. See the calculator disclaimer.

The volume is certain; the tonnage is not

A gravel takeoff has two halves with very different reliability, and most calculators blur them together. Area times depth divided by 27 is arithmetic — it is exactly right, every time. Converting those cubic yards into tons requires a unit weight, and unit weight is a measured property of one quarry’s product on one day, determined by a laboratory test (ASTM C29). It is not a constant of nature.

So this tool reports cubic yards as the reliable figure and tons as a conversion you can see and change. The presets come from WSDOT’s published estimating table, which is genuinely authoritative for the materials it lists. What it is not is universal: gravel from a different geology, screened differently, at a different moisture content, will weigh differently. When your supplier quotes a tons-per-yard figure, theirs wins.

Truck measure versus compacted on roadway

The detail almost every gravel calculator drops is that the same material has two unit weights. WSDOT lists crushed surfacing base course at 1.48 tons per cubic yard in truck measure and 1.85 compacted on the roadway. Ballast runs 1.55 loose against 1.95 placed. The material has not changed — the air between the stones has.

This matters twice. It is why you compute tonnage against the compacted figure, because that is the volume you are actually filling. And it is why a delivery looks alarmingly large next to the area you are covering: the same tonnage occupies roughly a quarter more space loose in the truck than it will once rolled. The working below shows both numbers so nobody has to guess whether they were shorted.

What this will not tell you

It will not tell you how deep to go. Spread depth for a driveway depends on traffic loading, subgrade strength, drainage and frost, and a number pulled off a calculator page is not a substitute for a spec or a local engineer. The 4 inches the tool opens with is a starting value so the maths has something to chew on, not advice.

It also will not price pea gravel, river rock or decomposed granite from a preset, because those are landscape materials rather than DOT pay items and no authoritative table covers them. Enter your supplier’s tons per cubic yard instead. Inventing a plausible-looking average and presenting it beside genuinely sourced figures would make the sourced ones worth less.

Sources

Grouped by manufacturer or publisher, then by document. Expand a group for the cited document, its verified-on date, and every value taken from it — all of it stays in the HTML either way.

Other sources(3 documents, 3 values)

Frequently asked questions

How much gravel do I need for a driveway?

Work the volume first, then convert. A 40 ft × 12 ft driveway is 480 sq ft; at 4 inches deep that is 160 cubic feet, which is 5.93 cubic yards. Add 10% for spread variation and you are ordering about 6.5 cubic yards, or roughly 12 tons of gravel base at 1.85 tons per cubic yard. The depth is the part nobody can answer for you — it depends on traffic, subgrade and whether this is a new build or a top-up.

How many tons of gravel are in a cubic yard?

There is no single number, and any calculator that gives you one without qualification is guessing. WSDOT publishes 1.85 tons per cubic yard for gravel base as its recommended estimating factor, but the same table notes it rises toward 1.90 where the grading is coarse and falls to about 1.70 where the material is largely sand. Aggregate unit weight is a measured property of a specific quarry’s product, tested to ASTM C29, so your supplier’s figure beats any published average.

Why does the gravel delivered look like more than I ordered?

Because it is more, by volume. WSDOT publishes two unit weights for the same material: truck measure, loose as delivered, and compacted on roadway. Crushed surfacing base course is 1.48 tons per cubic yard loose but 1.85 compacted. The tonnage does not change — mass is mass — but the same weight occupies roughly 25% more space in the truck than in the finished layer. This calculator shows both so the delivery is not a surprise.

Should I order gravel by the ton or by the yard?

Most suppliers sell by the ton because a truck scale is unambiguous while a loose cubic yard is not. That is precisely why the conversion matters: you measure a hole in cubic yards and pay for it in tons, and the factor connecting them belongs to the material. Ask what unit weight the quote assumes. If the supplier cannot tell you, that is worth knowing before the truck arrives.

Does this calculator work for pea gravel?

Only if you supply the unit weight. Pea gravel, river rock and decomposed granite are landscape materials rather than DOT pay items, so they do not appear in the WSDOT table this tool cites. Choose “My supplier’s figure” and enter the tons per cubic yard from your quote. We would rather ask you for a real number than invent an average and dress it up as sourced.

How much extra gravel should I order?

The calculator starts at 10% and keeps it adjustable. Unlike a tile or drywall waste factor, this is not about offcuts — bulk aggregate does not really produce waste. It covers spread variation, an uneven subgrade that swallows more than the nominal depth, and the fact that a second delivery costs another haul fee. A smooth, well-prepared base needs less; a rutted subgrade can need considerably more.