Tonnage Calculator

How to use this tonnage calculator

What this calculator does. This tool estimates how much aggregate material is required to cover a rectangular area at a chosen depth. It converts project dimensions into area, volume, net metric tonnes, an order quantity that includes wastage, and an estimated material cost. It is useful for early planning and supplier conversations, but it does not replace a site survey, geotechnical specification, compaction test, or supplier-certified bulk density.

When to use it. Use the calculator when estimating crushed stone beneath a slab, gravel for a driveway, sand for bedding, or topsoil for landscaping. It is also helpful for comparing how a deeper layer, denser material, or larger waste allowance changes the amount you need to purchase.

How to calculate. The calculator opens with a complete demonstration: crushed stone, a 10 m by 5 m area, 10 cm depth, 10% wastage, and a price of $45 per metric tonne. The example is already calculated and its Excel workbook is immediately available.

1. Select the Material. The calculator fills a representative unit weight, which you can replace with a project-specific value.
2. Enter Length and Width in meters, then enter Depth in centimeters.
3. Set the Wastage allowance to cover handling losses, uneven subgrade, and ordering uncertainty. Enter zero when no allowance is desired.
4. Optionally enter Price per metric tonne to estimate material cost, then review the live results and calculation table.
5. Select Download Excel to export the current validated inputs and outputs. Reset clears the demonstration and all calculated data; the export becomes unavailable until a new complete valid state is entered.

Input guide. Material is required and chooses a representative dry or bulk unit weight. Select “Custom unit weight” when your supplier provides a tested value. Unit weight is required, accepts a positive decimal in kg/m³, and directly scales tonnage: doubling density doubles mass. A realistic crushed-stone example is 1,650 kg/m³. Do not confuse bulk density with solid particle density. Length and Width are required positive decimal values in meters; 10 m and 5 m are valid examples. Their product is the covered area, so doubling either dimension doubles area, volume, and tonnage. Depth is required in centimeters; 10 cm means 0.10 m in the volume formula. A common mistake is entering millimeters as centimeters. Wastage allowance is optional, accepts 0 – 100%, and increases only the order quantity and cost, not the geometric volume. Price per metric tonne is optional, accepts a nonnegative U.S.-dollar amount, and changes cost without changing physical quantity.

Output guide. Area is the exact rectangular footprint in square meters. Volume is the estimated loose or placed material space in cubic meters based on the entered depth. Net tonnage is volume multiplied by unit weight and converted from kilograms to metric tonnes. Order tonnage adds the selected wastage allowance; a zero allowance makes it equal to net tonnage. Estimated material cost multiplies order tonnage by price per metric tonne; it is zero when price is zero and excludes tax, delivery, minimum-load charges, and labor. The calculation breakdown table shows each stage, formula basis, numerical value, and unit.

Worked example. With 10 m length and 5 m width, the area is 50.00 m². A depth of 10 cm is 0.10 m, so volume is 50.00 × 0.10 = 5.00 m³. At 1,650 kg/m³, net mass is 8,250 kg, or 8.25 metric tonnes. Adding 10% gives 9.075 tonnes, displayed as 9.08 t. At $45 per tonne, the estimated material cost is $408.38.

Learn more. The formula follows the standard relationship between mass, volume, and density. For unit definitions and SI conversion practice, see the NIST guidance on SI units of mass and the NIST guidance on SI units of volume.