Gravel Calculator
In-place depth, loose order: the compaction factor and the density that turn a rectangle into the tons the quarry sells.
Gravel Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Rectangles at uniform depth.
- Compaction percentages are planning bands, not lab values.
- No subgrade-loss allowance — that rides in waste on soft ground.
In short: A 20 × 24 ft base at 4 in compacted: 5.925926 yd³ in place — exactly the slab's own volume — 7.111111 yd³ of crusher run ordered at ×1.20, 10.311111 tons. One 10-yd truck covers it; each ton of base spreads 55.86 ft² at this depth.
Formula
in-place yd³ = ft² × finished depth ÷ 324
loose order = in-place × (1 + compaction)
tons = loose × material density
one ton covers = 27 × 12 ÷ depth ÷ density ft²
[('finished depth', 'after the plate compactor, not before'), ('the shrink', 'dense base 15-25%, clean stone ~10%'), ('the scale', 'per-material density, wet loads heavier'), ('324', 'ft² × inches → yd³, exactly')]
Worked Example
- Convert the finished rectangle to in-place yards via 324.
- Inflate by the compaction allowance for the loose order.
- Convert to tons with the ordered material's density.
- State truck loads and the coverage of a single ton.
- Show the bag absurdity that justifies bulk.
20 × 24 ft at 4-in finished: 5.925926 yd³ in place (identical to the slab above it), 7.111111 yd³ loose at ×1.20, 10.311111 tons of crusher run at 1.45. That is 0.71 of a 10-yd truck, 55.86 ft² per ton — and 320 bags nobody wants to lift.
Strengths & Limits Of This Model
Where this engine is strong
- Compaction and density kept separate and explicit
- Per-ton coverage for unit-hopping quotes
- The 324 identity taught, not hidden
Where it stops
- Uniform depth only
- No gradation guidance beyond chips
Practical Use Cases
Slab bases
The compacted course under concrete.
Driveways
Deep bases priced by the ton.
Paths & pads
Thin finishes, bag-vs-bulk decisions.
Drainage layers
Clean stone at its own density.
Quote checks
Ton quotes against area and depth.
Methodology & Editorial Standards
In-place volume is ft² × finished depth ÷ 324 (exact identity). The loose order multiplies the compaction allowance; tonnage multiplies the material density with chips labelling common stone. Coverage divides one ton by density and by depth; truck loads use a 10-yd reference; the bag card converts in-place volume at 0.5 ft³ per sack to make bulk's case. Zero dimensions or density are refused.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Gravel Calculator — 10 Expert FAQs
10 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How many tons of gravel do I need?
In-place yards from ft² × inches ÷ 324, times the compaction allowance, times the material's density. The 20 × 24 ft base at 4 in: 5.9259 × 1.20 × 1.45 = 10.31 tons of crusher run.
How much does a cubic yard of gravel weigh?
Depends on the stone: crushed stone and pea gravel run about 1.4 tons per loose yard, crusher run 1.45, dry sand 1.35, riprap nearer 1.85. Wet loads add 10-15% to any of them.
Why do I need more gravel than the hole measures?
Because the finished depth is measured after compaction, and dense-graded base shrinks 15-25% under a plate compactor. Order in-place × 1.20 for crusher run and finish at the depth you wanted.
How deep should a gravel base be under concrete?
4 inches compacted is the residential slab norm, more under drives or soft ground. The depth decision belongs to your plans and soils; this page prices whichever depth you enter.
What is the 324 rule?
Square feet × depth in inches ÷ 324 = cubic yards. An inch over a square foot is 1/12 of a cubic foot, and a yard is 27 of those — 12 × 27 = 324. It is exact, not an approximation.
Crusher run or clean stone?
Crusher run (dense grade) locks into a load-bearing base and needs the compaction allowance; clean stone drains but does not lock, settling nearer 10%. Base under concrete is crusher-run territory; drainage layers are clean stone's.
How much area does a ton of gravel cover?
At 4-in finished depth, about 56 ft² for 1.45-ton material — divide 324 by the depth in inches and by the density. Halve the depth, double the coverage.
Is gravel sold by yard or ton?
Both exist, often at the same quarry. The truck delivers loose volume; the scale weighs it. Convert with the material's density before comparing quotes in different units — the page's two cards are that conversion.
Can I just use bags of gravel?
The worked example's in-place volume is 320 landscape sacks — about 8 tons of lifting and plastic. Bags earn their keep under a dozen sacks; past that the delivered ton is cheaper and kinder.
Does wet gravel change the order?
The volume you need does not change; the scale does — wet stone can weigh 10-15% more per yard. If you buy by the ton in a rainy week, the truck carries less volume per ticket; by the yard, you carry the weather risk instead.