How to use
- Measure the area inside the border that will retain the loose stone.
- Select the playground planning preset or enter your own patio or custom fill depth.
- Replace the density with the yard's figure if available, and add an order allowance only if your plan requires one.
How the estimate is calculated
Fill volume in cubic feet is contained area × depth in inches ÷ 12. Divide by 27 for cubic yards. The order multiplier is 1 + additional allowance ÷ 100, and order yards × density gives short tons. Half-cubic-foot bag equivalents round up from order cubic feet ÷ 0.5.
Example: a 200 sq ft contained area at 12 in initial fill has 200 cu ft of gravel. With 0% additional allowance, that is 7.41 cubic yards, about 10.00 tons at 1.35 short tons per cubic yard, or 400 bags of 0.5 cu ft. This illustrates quantity only, not a safe equipment fall height.
Initial fill and maintained depth
| Planning reference | Figure | Use in this tool |
|---|---|---|
| Initial loose-fill preset | 12 in | Commonly used planning figure; user must confirm |
| Maintained-depth comparison | 9 in | Commonly used planning figure, not a performance certification |
| Reduction from 12 to 9 in | 25% | Calculated depth comparison |
| Density example | 1.35 short tons/cu yd | Derived from 50 lb per 0.5 cu ft bag summary |
The playground guidance was reviewed only as search summaries. Those summaries do not establish an official depth requirement or a certified fall-height rating here. The initial and maintained figures are quantity-planning comparisons. Check current surfacing instructions for the equipment, location, and material before choosing a depth.
Keep loose fill contained
A border defines the measured area, but movement and displacement can leave low spots where the stone is used most. Plan how the depth will be checked and replenished. A blanket extra percentage does not replace a maintained-depth plan, and the preset already represents an initial fill rather than a thin top-up.
Patios need a different decision
Rounded pea gravel moves underfoot, so select a depth and edge detail for the intended walking or seating surface. The custom input does not prescribe a patio depth. Crushed aggregate and sand have different roles and weight assumptions; estimate those separately if your patio design includes them.
Common mistakes
- Applying a maintained-depth quantity to an initial-fill plan.
- Assuming a yardage result certifies protection for a particular fall height.
- Adding the preset and a second compression allowance without checking the plan.
- Ordering by tons with a density borrowed from a different stone product.
Sources
Planning context: CPSC Public Playground Safety Handbook, Iowa DPH loose-fill guidance, and NDSU FN1374, reviewed only as search summaries. No numerical fall-height claim is made from these summaries. Density is a planning derivation from the summarized Quikrete All-Purpose Gravel bag listing: 50 ÷ 0.5 × 27 ÷ 2,000 = 1.35 short tons/cu yd.
Related calculators
- Gravel Calculator — aggregate presets for other stone work
- Sand Calculator — a sand layer rather than rounded stone
- Paver Calculator — unit paving and its base
Frequently asked questions
Does this certify a playground surface?
The output measures material volume only. It does not certify fall protection, material suitability, or equipment compliance.
What does the playground preset change?
It fills the depth field with 12 in, or 30.48 cm in metric. This is an initial-fill planning figure that you must verify for your project.
How is the density estimated?
The default comes from a summarized 50 lb, 0.5 cu ft bag yield, equivalent to 1.35 short tons per cubic yard. Replace it with the supplier value.
Can I calculate a shallow patio layer?
Choose patio or custom and enter that layer depth. The calculator supplies the quantity without choosing a suitable patio design.
Does the bag count change with stone density?
Bag equivalents use volume. A density adjustment changes tonnage while the same volume still requires the same half-cubic-foot equivalents.