Free trap rock driveway calculator (tons)
Estimate tons of trap rock (dense crushed volcanic/igneous aggregate) for a driveway surface or base layer. Default densities (~100–120 lb/ft³) are planning only — quarries and moisture vary. For a hot-mix asphalt layer on top, use the asphalt calculator or driveway asphalt tool. Related: gravel / asphalt base calculator.
Notes
Trap rock is dense crushed volcanic or other igneous rock sold as driveway gravel, base stone, or a dressed surface. Angular faces lock under compaction better than many rounded river gravels — but density, size, and fines still depend on the quarry blend you actually buy.
Formula matches our base and asphalt tools: volume (ft³) × density ÷ 2000, then waste. A common residential planning thickness for a trap-rock surface or base lift is often in the 3–4 inch compacted range (more on soft soils or steep grades) — follow your contractor or engineer.
Confirm density and gradation with your quarry before ordering. Next: estimate asphalt tons on the main asphalt calculator, size a crushed-stone base with the asphalt base / gravel calculator, or read the trap rock driveway guide.