1. Convert measurements to feet
Feet = inches ÷ 12. Dimensions and depth are converted independently. One cubic yard is exactly 27 cubic feet (3 feet × 3 feet × 3 feet).
2. Calculate each area
- Rectangle: length × width.
- Circle: π × radius². We use JavaScript’s full available π precision.
- Triangle: base × perpendicular height ÷ 2.
3. Find the volume
Cubic feet = square feet × depth in feet
Cubic yards = cubic feet ÷ 27
Each area has its own depth. Volumes are added only within the same material group. A mulch area and a soil area never combine into a single purchase quantity.
4. Optional extra allowance
Purchase target = measured volume × (1 + allowance ÷ 100)
The default is zero percent. Any allowance is a user choice, not a recommendation. The measured need, added allowance, and purchase target are shown separately.
5. Whole bags
Bags = ceiling(purchase target ÷ bag volume)
Purchased volume = bags × bag volume
A bag cannot be split for purchase. Purchased volume minus target is the amount above the purchase target. Purchased volume minus measured need includes both the allowance and order rounding.
6. Bulk order rule
Valid orders start at the minimum and increase by a whole number of increments. The minimum does not have to be an exact multiple of the increment.
Order = minimum + ceiling(max(0, target − minimum) ÷ increment) × increment
All terms here use cubic yards. A 1.2 cu yd minimum and 0.5 cu yd increment permits 1.2, 1.7, 2.2, and so on. For a supplier selling only absolute multiples, enter a compatible minimum. If the supplier uses different rules, confirm the quantity outside this tool.
A zero requirement produces no material order in the calculation engine. The interface requires positive dimensions and depth, and removing all areas clears the estimate.
7. Purchase costs
Material cost is whole bags × bag price, or ordered cubic yards × bulk unit price. Total = material cost + delivery + other fixed fee. Both options support delivery and fixed fees.
A blank price or fee is unknown. No cheaper option is selected until every cost field is complete. The optional other fee initially displays zero; the user must replace it when a fee applies. Sales tax is excluded. No location-based tax, discounts, delivery eligibility, product availability, or market prices are inferred.
8. Rounding and precision
Volumes display up to three decimal places. Positive quantities below 0.001 display as “Under 0.001”, rather than zero. Purchase calculations retain the unrounded floating-point values. Only numerical noise within eight machine-epsilon units of a whole count is treated as that whole count, to avoid a phantom extra bag from binary arithmetic.
Money is displayed to the nearest cent. The cheaper-option comparison uses those cent-rounded total estimates. Supplier invoices may round individual line items differently. A tiny displayed volume is not permission to skip the calculated whole-bag order.
9. Input limits
Up to 20 areas. Each dimension must be at least 0.001 and no more than 10,000 in the selected dimension unit. Depth must be at least 0.001 in the selected unit and is limited to 120 inches or 10 feet. Allowance is 0–100%. Custom bags must be at least 0.001 and no more than 100 cu ft. Prices and fees are 0–$1,000,000. Bulk minimums and increments are limited to 1,000,000 cu yd, with an increment of at least 0.001 cu yd.
10. What this tool cannot determine
Uniform depth and idealized shapes are approximations. Compaction, moisture, settling, irregular terrain, product suitability, and installation requirements are not modeled. This is a planning estimate, not a site inspection or supplier quote. Verify measurements and ordering terms before buying.
Measurement reference
The foot-to-inch and yard-to-foot relationships follow standard U.S. customary length units. See the NIST Guide for the Use of the International System of Units for measurement and conversion references. The area and purchase rules above are fully stated here; no external product dataset is used.