It’s one of the most common questions before a landscape delivery: how much do I actually need? Order too little and you’re scheduling a second delivery. Order too much and you’ve got a pile of leftover material taking up space in the yard.
Decorative stone is sold by the cubic yard or by the ton, and the math to get from your bed dimensions to a delivery quantity is straightforward — once you know the formula. This guide walks you through it step by step, with examples for the most common applications.
The Basic Formula
All decorative stone quantity calculations use the same core formula:
Length (ft) × Width (ft) × Depth (ft) ÷ 27 = Cubic Yards
The only thing that trips people up is the depth — which needs to be in feet, not inches. Here are the most common depth conversions:
| Depth | In Feet |
|---|---|
| 1 inch | 0.083 ft |
| 2 inches | 0.167 ft |
| 3 inches | 0.25 ft |
| 4 inches | 0.333 ft |
For most decorative stone applications — garden beds, tree circles, pathway borders — 2 to 3 inches of depth is the standard recommendation. That’s enough to suppress weeds and provide good coverage without the stone feeling too deep or unstable underfoot.
What Depth Should You Use?
2 inches: Appropriate for top-dressing an existing stone bed or adding a thin decorative layer where weed suppression is already handled by landscape fabric.
3 inches: The standard recommended depth for new decorative stone installations in garden beds and planting areas. Provides solid weed suppression and good visual coverage.
4+ inches: Used for drainage applications, dry creek beds, and high-traffic areas where stability and depth of coverage matter more than appearance alone.
Calculating for Common Applications
Example 1: Foundation Planting Bed
A typical ranch-style home front bed might run 40 feet long and 4 feet wide.
- 40 × 4 × 0.25 (3-inch depth) = 40
- 40 ÷ 27 = 1.48 cubic yards → order 1.5 yards
Example 2: Around a Tree
A tree circle with a 6-foot diameter has a radius of 3 feet. Area = π × r² = 3.14 × 9 = 28.3 square feet.
- 28.3 × 0.167 (2-inch depth) = 4.7
- 4.7 ÷ 27 = 0.17 cubic yards
Tree circles are small enough that you’d typically combine this order with another area to make a delivery quantity worthwhile — most minimum orders are 1 cubic yard.
Example 3: Side Yard Strip
A side yard 50 feet long and 6 feet wide at a 3-inch depth:
- 50 × 6 × 0.25 = 75
- 75 ÷ 27 = 2.78 cubic yards → order 3 yards
Example 4: Dry Creek Bed
Creek beds are irregular in shape, so estimate conservatively and round up. A creek bed approximately 30 feet long, averaging 3 feet wide, at a 4-inch depth:
- 30 × 3 × 0.333 = 29.97
- 29.97 ÷ 27 = 1.1 cubic yards → order 1.5 yards (rounding up accounts for irregular edges and depth variation)
Example 5: Full Backyard Renovation
Multiple areas being done at once — always calculate each zone separately, then add them together for the total order.
| Area | L × W | Depth | Cu. Yards |
|---|---|---|---|
| Front bed | 40 × 4 | 3″ | 1.5 |
| Side yard | 50 × 6 | 3″ | 2.8 |
| Tree circles (3) | — | 2″ | 0.5 |
| Fire pit surround | 12 × 12 | 3″ | 1.3 |
| Total | 6.1 yards |
Cubic Yards vs. Tons: Which Does Mulch & More Use?
Mulch & More sells decorative stone by both cubic yard and ton depending on the product. Here’s the practical difference:
- Cubic yards measure volume — how much space the material takes up. This is the most useful measurement for calculating coverage.
- Tons measure weight. River rock and larger decorative stone are often sold by the ton because stone is dense and weight is a more accurate measure of how much material you’re getting.
As a general conversion: 1 cubic yard of river rock or decorative stone weighs approximately 1.3 to 1.5 tons depending on the size and type of stone. When in doubt, use the materials calculator on the Mulch & More website — it handles both cubic yard and tonnage calculations for stone.
Always Round Up
When your calculation lands on a fraction, round up to the next half yard. Here’s why: it’s much easier to have a small amount of leftover material than to run short and need a second delivery. Leftover decorative stone stores easily — spread a tarp over it or pile it out of the way until you find a use for it. Running short mid-project is a much bigger disruption.
Also factor in:
- Edging losses — A small amount of stone will end up outside the bed during installation. Add 5–10% to your estimate if your bed has a lot of perimeter edging.
- Settling — Stone settles slightly after the first rain. What looks like adequate coverage initially may look thinner after a wet week. The standard recommendation accounts for this, but it’s worth knowing.
- Irregular shapes — For curved or irregularly shaped beds, break them into approximate rectangles, calculate each section, and add them together.
Not Sure? We Can Help.
If you’re still unsure how much to order, Mulch & More’s team is happy to help you work through the calculation before you place an order. We’d rather help you get it right the first time than have you short or over on material.
Use the online materials calculator → Shop decorative stone and river rock → View delivery information → Contact us with questions → | (610) 644-8086
We serve Chester County, Delaware County, and Montgomery County with same-day and next-day delivery available on most orders.
