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Gravel Volume, Weight, Coverage, and Cost Formulas

Review formulas for gravel area, cubic yards, bulk density, US tons, metric tonnes, extra material, coverage, truckloads, and material cost.

How do the Gravel Calculator formulas work?

This formula page defines the variables used by the Gravel Calculator, shows how those values are combined, and explains the order of operations behind the result. Use the worked steps to verify an estimate, compare scenarios, and understand which assumptions or rounding rules can affect the displayed answer.

Formula Overview

The engine normalizes dimensions and density, calculates the rectangular volume, converts volume to material weight, applies the entered extra-material allowance, and then estimates whole truckloads and optional material cost.

Variable Definitions

  • L: length and W: width
  • D: finished gravel depth
  • q: number of identical areas
  • ρ: entered bulk density
  • e: entered extra-material percentage
  • C: entered usable truck capacity
  • P: entered price per weight unit

Area and Net Volume

A=L×W×qA=L\times W\times q
Vnet=A×DV_{net}=A\times D
Vyd3=Vft327V_{yd^3}=\frac{V_{ft^3}}{27}

All dimensions are normalized before multiplication. When depth is entered in inches, it is divided by 12 before a cubic-foot volume is calculated.

Weight and Tonnage

Weightlb=Vft3×ρlb/ft3Weight_{lb}=V_{ft^3}\times\rho_{lb/ft^3}
US tons=Weightlb2000US\ tons=\frac{Weight_{lb}}{2000}
Metric tonnes=US tons×0.90718474Metric\ tonnes=US\ tons\times0.90718474

The volume-to-weight result is only as representative as the entered bulk density.

Extra Material, Truckloads, and Cost

Order weight=Net weight(1+e100)Order\ weight=Net\ weight\left(1+\frac{e}{100}\right)
Truckloads=⌈Order weightC⌉Truckloads=\left\lceil\frac{Order\ weight}{C}\right\rceil
Material cost=Order weight×PMaterial\ cost=Order\ weight\times P

Capacity and price are converted to the same US-ton or metric-tonne basis before these calculations. Truckloads round up to a whole planning load.

Coverage Per US Ton

Coverageft2/ton=2000ρlb/ft3×DftCoverage_{ft^2/ton}=\frac{2000}{\rho_{lb/ft^3}\times D_{ft}}

Coverage falls when finished depth or density increases. It is a mathematical planning result, not a supplier guarantee.

Unit Conversions

  • 12 inches = 1 foot
  • 3 feet = 1 yard
  • 1 cubic yard = 27 cubic feet
  • 1 foot = 0.3048 meters
  • 1 cubic foot = 0.028316846592 cubic meters
  • 2,000 pounds = 1 US ton
  • 1 US ton = 0.90718474 metric tonnes

The engine uses Decimal.js for the intermediate unit calculations. Displayed calculator values are rounded to two decimal places.

Worked Gravel Calculation

For a 20 ft × 10 ft area at 4 in finished depth:

V=20×10×412=66.667 ft3V=20\times10\times\frac{4}{12}=66.667\ ft^3
Vyd3=66.66727=2.469 yd3V_{yd^3}=\frac{66.667}{27}=2.469\ yd^3

At 100 lb/ft³, net weight is 6,666.67 lb or 3.333 US tons. With 10% extra material, order volume is about 2.716 yd³ and order weight is about 3.667 US tons.

Assumptions and Boundaries

  • Entered areas are uniform rectangles.
  • Depth is the finished gravel thickness.
  • Bulk density applies uniformly to the selected material.
  • The extra percentage is applied after net volume and weight.
  • Truckloads and cost use the entered capacity and price basis.
  • Supplier rounding, delivery fees, and site design are excluded.

Use the Gravel Calculator