Riprap Weight Per Cubic Yard, Explained
Ask three suppliers how much a cubic yard of riprap weighs and you might get three different answers — not because anyone’s wrong, but because “riprap density” depends on the source rock, the stone size, and how much empty space sits between the stones once they’re placed. Understanding that variance is what makes a conversion actually reliable instead of a guess.
Quick answer
Placed riprap typically weighs 1.3 to 1.7 tons per cubic yard — limestone runs toward the lighter end (~1.35-1.45), granite and basalt toward the heavier end (~1.5-1.7). To go from yards to tons, multiply by your density. To go from tons to yards, divide by it. Both directions and a full conversion table are below.
The Riprap / Rock Calculator handles this conversion automatically from your area, thickness, and rock class.
Why riprap weight varies so much by source
Two different things get called “riprap density,” and mixing them up is exactly why online figures don’t agree.
- Particle density (solid rock)The weight of the stone material itself, with no gaps — typically 155-165 lb/cu ft for quarried rock (specific gravity around 2.5-2.65).
- Bulk density (placed riprap)The weight of a cubic yard of riprap as it actually sits on the ground — stones plus the empty gaps (voids) between them, which is always lower than particle density.
The relationship: bulk density = (1 − porosity) × particle density. Riprap’s porosity — the fraction of its placed volume that’s actually empty space — typically runs 20-40%, which is why bulk density comes in meaningfully lower than the density of the rock itself.
Placed density by rock material
| Material | Placed density (tons/cu yd) |
|---|---|
| Limestone | 1.35 – 1.45 |
| Granite / basalt | 1.50 – 1.70 |
| General crushed stone average | 1.30 – 1.60 |
Granite and basalt run denser than limestone at the mineral level, and that difference carries through even after accounting for voids — always confirm the specific density with your supplier, since “riprap” alone doesn’t specify the source rock.
Placed density by rock class
| Class | Density (lb/cu ft) | Density (tons/cu yd) |
|---|---|---|
| Light | 115 | 1.55 |
| Medium | 120 | 1.62 |
| Heavy | 125 | 1.69 |
These sit toward the denser end of the general material range above, reflecting well-compacted, well-graded placement — actual site density can run lower with looser, dump-and-spread placement rather than careful machine placement.
Converting cubic yards to tons
| Cubic yards | Tons |
|---|---|
| 10 | 16.2 |
| 25 | 40.5 |
| 50 | 81.0 |
| 100 | 162.0 |
Converting tons to cubic yards
| Tons | Cubic yards |
|---|---|
| 20 | 12.3 |
| 50 | 30.9 |
| 100 | 61.7 |
| 200 | 123.5 |
Notice this is the reciprocal relationship of the previous table — the same density figure works in both directions, just multiply one way and divide the other.
What to confirm before converting
- Rock class or materialDetermines which density figure applies — don’t use a generic average when you know the specific class or source rock.
- Whether the quote is for solid or placed volumeParticle density and bulk density give very different results if confused.
- Placement methodMachine-placed, well-graded riprap tends toward the denser end of a given range; loose dump-and-spread tends lower.
- Supplier-confirmed densityThe most reliable number for a real order is whatever your specific supplier tests and quotes, not a generic table.
Worked examples
Example 1 — 60 cubic yards of medium riprap, converting to tons
60 × 1.62 = 97.2 tons.
Example 2 — a supplier quote of 150 tons, converting to cubic yards
150 ÷ 1.62 = 92.6 cubic yards.
Example 3 — same 100 tons, limestone vs. granite
- Limestone (1.40 tons/cy)100 ÷ 1.40 = 71.4 cu yd
- Granite (1.60 tons/cy)100 ÷ 1.60 = 62.5 cu yd
The same 100 tons covers noticeably less volume in denser granite than in lighter limestone — worth knowing if you’re comparing quotes priced by the ton across different source rock.
Skip the manual conversion.
Enter your area, rock class, and thickness for an instant tons and cubic yard result together.
Use the free Riprap / Rock CalculatorMistakes converting riprap weight and volume
- Using solid rock density instead of placed (bulk) densityOverstates tonnage significantly, since it ignores the real voids between placed stones.
- Applying one generic density to every materialLimestone and granite differ enough that a single average can meaningfully misstate an order.
- Assuming density is the same across all rock classesLarger, heavier classes generally run somewhat denser once placed.
- Mixing up the direction of the conversionMultiplying when you should divide (or vice versa) gives a result off by the square of the density figure.
- Not confirming density with the actual supplierGeneric planning figures are a starting point — a specific quarry’s tested density is the number that should drive a real order.
Quick reference: density by class, both directions
| Class | Density (tons/cy) | 1 ton = | 1 cu yd = |
|---|---|---|---|
| Light | 1.55 | 0.65 cu yd | 1.55 tons |
| Medium | 1.62 | 0.62 cu yd | 1.62 tons |
| Heavy | 1.69 | 0.59 cu yd | 1.69 tons |
What most affects the real density
- Source rock mineralogyGranite and basalt run denser than limestone at the same class.
- Void ratio (porosity)Typically 20-40% for placed riprap, and the single biggest reason placed density is lower than solid rock density.
- Placement methodCareful machine placement tends toward less void space than loose dumping.
- Stone size and gradationHow well smaller stones fill the gaps between larger ones affects final bulk density.
Convert accurately in five steps
- Identify your rock class or material rather than using a generic average.
- Confirm whether you have solid or placed (bulk) density.
- Multiply cubic yards by density for tons, or divide tons by density for cubic yards.
- Double-check the direction of your conversion before ordering.
- Confirm the exact density with your supplier before finalizing a large order.
Frequently asked questions
How much does a cubic yard of riprap weigh?
Typically 1.3 to 1.7 tons, depending on rock class and source material — limestone toward the lighter end, granite and basalt toward the heavier end.
Why do different sources give different riprap density figures?
Because “density” can mean either solid rock density (no voids) or placed bulk density (including the real gaps between stones) — these are genuinely different numbers, not just imprecise estimates.
How do I convert cubic yards of riprap to tons?
Multiply cubic yards by your rock class’s density in tons per cubic yard — for medium riprap at 1.62 tons/cy, 50 cubic yards equals 81 tons.
How do I convert tons of riprap to cubic yards?
Divide total tons by the density in tons per cubic yard — 100 tons of medium riprap at 1.62 tons/cy equals about 61.7 cubic yards.
Is granite riprap heavier than limestone riprap?
Yes, generally — granite and basalt run 1.50-1.70 tons per cubic yard placed, compared to limestone’s 1.35-1.45, due to the denser mineral composition.
What percentage of placed riprap is empty space?
Typically 20-40% porosity (voids) between the stones, which is the main reason placed bulk density is meaningfully lower than the density of the solid rock itself.
Does riprap size affect its placed density?
Somewhat — larger stone classes tend to run slightly denser once placed in this guide’s planning figures, though real-world variance by site and placement method can be significant.
Should I trust a generic density figure or ask my supplier?
Ask your supplier for a large order. Generic figures are a solid planning starting point, but actual quarry material can vary enough to matter on a significant purchase.
Related reading
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