How to Calculate Bulk Materials for a Landscape or Hardscape Job

For landscapers and hardscapers, buying bulk materials can be a great way to reduce costs, minimise waste, and keep projects moving smoothly. However, getting the right amount of material from the start is key to staying on budget and on schedule. Order too little, and you’re scrambling to make up the difference. Order too much, and you’re stuck with extra materials that take up space and eat into your profits.

Taking the time to measure and calculate properly before placing a bulk order helps you avoid common project pitfalls and go forward with confidence. Below, we’ll walk through some formulas and factors that go into bulk material calculations.

Benefits of Bulk Materials

Buying in bulk, first and foremost, generally saves money. It also makes jobs more efficient and organized. With materials delivered in the right quantity, work stays on schedule and there’s no need to wait for additional deliveries. Ordering properly also means less waste, which keeps costs down and prevents unnecessary cleanup at the end of a job.

Material consistency is another advantage. Bulk orders help maintain uniformity in colour, texture, and quality, which can otherwise be challenging when working with stone, mulch, and soil. Small batch orders can lead to slight variations that are noticeable once installed, especially on large-scale projects. When everything comes from the same delivery, the finished product looks seamless.

Bulk materials can also help reduce a project’s environmental impact. Fewer deliveries mean lower fuel use, and bulk orders typically come with less packaging waste. On-site, this means fewer bags and containers cluttering up the work area. Planning ahead and calculating materials properly allows you to take full advantage of these benefits while keeping jobsites efficient and professional.

Calculating Stone Needs

Stone is a key component in many outdoor projects, including patios, pathways, and retaining walls. Ordering the right amount depends on the area to be covered, the depth of installation, and the type of stone being used. Decorative gravel typically requires a 2–3-inch depth, whereas a paver base or driveway foundation needs a deeper layer for stability.

To determine how much stone you need, start by measuring the length and width of the project area. Depth is equally important—gravel for decorative use may only need 2 inches, but a base layer for driveways and patios generally requires 4 to 8 inches. Once you have the dimensions, you can use the following formula to calculate the total volume in cubic yards:

(Length × Width × Depth) ÷ 27 = Cubic Yards Needed

Example Calculation

For a patio base that’s 20 feet long, 10 feet wide, and 4 inches (0.33 feet) deep:

(20 × 10 × 0.33) ÷ 27 = 2.44 cubic yards

If you’re ordering by weight, most crushed stone weighs between 1.4 and 1.7 tons per cubic yard. You can use this range to convert a volume-based estimate into tonnage, which is how many suppliers price bulk stone.

Calculating Road Base

Road base provides stability beneath patios, driveways, and other hardscapes. It consists of compactable materials like crushed rock and gravel, which form a solid foundation for the surface above. Since road base compacts over time, it’s important to order extra material to account for shrinkage. A good rule of thumb is to add 10–15% more than the raw volume calculation.

The required depth depends on usage. Pathways and patios typically need a 4-inch base, while driveways or areas that support heavier loads require 6 to 8 inches. To calculate the total amount required, use the cubic yard formula and factor in compaction:

(Length × Width × Depth) ÷ 27 = Cubic Yards Needed

Example Calculation

For a driveway that’s 50 feet long, 10 feet wide, and 6 inches (0.5 feet) deep:

(50 × 10 × 0.5) ÷ 27 = 9.26 cubic yards

Since road base compacts, add 10%:

9.26 × 1.1 = 10.19 cubic yards

This adjusted estimate prevents shortages due to settling while ensuring the base remains structurally sound.

Calculating Mulch

Mulch enhances landscapes by helping with moisture retention, weed control, and insulation. Estimating the right amount depends on the application—light coverage requires about 2 inches, while flower beds and tree rings typically need 3 to 4 inches.

The same volume formula applies to mulch calculations:

(Length × Width × Depth) ÷ 27 = Cubic Yards Needed

Example Calculation

For a garden bed measuring 30 feet by 15 feet with 3 inches (0.25 feet) of mulch:

(30 × 15 × 0.25) ÷ 27 = 4.16 cubic yards

If purchasing bagged mulch, convert cubic yards into bags:

• 1 cubic yard = 27 cubic feet
• Standard mulch bags hold 2 cubic feet

To find the total cubic feet:

4.16 × 27 = 112.32 cubic feet

To determine the number of bags needed:

112.32 ÷2 = 56.16 bags

Since partial bags aren’t practical, it’s best to round up to 57 bags for full coverage. This slight overage accounts for any variations in application depth and avoids running short during installation.

Calculating Topsoil Needs

Topsoil is essential for new lawns, garden beds, and grading projects. It provides nutrients and improves soil structure for healthy plant growth. The depth needed varies—lawns typically require 4–6 inches, while garden beds may need 8–12 inches.

Using the same formula, determine the total volume in cubic yards:

(Length × Width × Depth) ÷ 27 = Cubic Yards Needed

Example Calculation

For a new lawn covering 40 feet by 20 feet with 5 inches (0.42 feet) of topsoil:

(40 × 20 × 0.42) ÷ 27 = 12.44 cubic yards

Remember, calculating correctly helps you avoid under-ordering, which can lead to uneven coverage, or over-ordering, which leaves excess soil to store or dispose.

Calculating Voltage Drop for Outdoor Lighting

For large-scale outdoor lighting installations, voltage drop can affect brightness and performance. Long wire runs create resistance, which reduces the power delivered to each fixture. If the voltage drop is too high, lights at the far end may appear dim or fail to function properly.

To estimate voltage drop, use the formula:

(Length × VA) × 2 ÷ Kc = Voltage Drop

Example Calculation

A 100-foot wire run carrying 150 volt-amperes on 12-gauge wire (constant = 7,500):

(100 × 150 × 2) ÷ 7,500 = 4V drop

If the system is running on a standard 12V tap, this would leave only 8V at the last fixture, which is too low for optimal performance. However, many multi-tap transformers offer up to 15V, meaning a 4V drop would still deliver 11V, which is typically sufficient.

To compensate for voltage loss, there are two main solutions:

• Using thicker gauge wire: Upgrading to 8 AWG wire reduces resistance and minimizes drop.
• Adding transformers along the run: This helps maintain consistent voltage across all fixtures.

Carefully assessing voltage drop and available transformer settings ensures proper brightness and reliable performance across the lighting system.

Wire Gauge Reference Chart

The following chart provides Kc values and corresponding amp/watt ratings for different wire sizes. When planning an installation, selecting a wire size with a higher Kc value can help reduce voltage drop and maintain consistent lighting performance.

Calculating Holiday Lighting Needs

For holiday displays, accurate measurements prevent wasted materials and provide even coverage. The key is knowing how many lights are required for rooflines, trees, and shrubs.

Roofline Lighting

For perimeter lighting, use this formula:

Perimeter Length ÷ Spacing Between Bulbs = Number of Bulbs Needed

Example Calculation

A 100-foot roofline with bulbs spaced every 12 inches (1 foot):

100 ÷ 1 = 100 bulbs

Tree and Shrub Lighting

Lighting trees and shrubs can be more involved, since coverage depends on whether you’re wrapping the trunk, branches, or canopy. Here’s how to calculate each:

Canopy Wrap

To estimate the lighting needed for a canopy wrap, calculate the canopy’s surface area and multiply it by 3.14 (π) to determine the total light strand length required.

Canopy Length × Canopy Width × 3.14= Total Light Length

Example Calculation
A tree canopy that measures 10 feet long by 8 feet wide:

10 × 8 × 3.14 = 251.2 feet of lights

Trunk Wrap

To wrap a tree trunk, determine the total number of spirals needed by factoring in the height of the trunk, the circumference, and the spacing between each ring of lights.

Trunk Height × Trunk Circumference ÷ Spacing Between Rings = Total Light Length

Example Calculation
For a tree with a 7-foot trunk height, 2-foot circumference, and lights spaced every 6 inches (0.5 feet):

7 × 2 ÷ 0.5 = 28 feet of lights

Branch Wrap

Branch wrapping requires a more detailed approach, because each tree varies in the number of branches and their lengths.

Number of Branches × Average Branch Length × Average Branch Diameter ÷ Ring Spacing = Total Light Length

Example Calculation
For 10 branches, each averaging 6 feet long, with an average diameter of 1 foot, and lights spaced every 6 inches (0.5 feet):

10 × 6 × 1 ÷ 0.5=120 feet of lights

Planning ahead results in a balanced look and prevents last-minute trips to busy stores for additional lights.

Find the Right Materials—and the Right Amount—for Your Next Job

At SiteOne® Landscape Supply, we provide high-quality bulk materials at competitive prices to help you complete your projects efficiently and cost-effectively. Whether you need stone, mulch, topsoil, road base, or other essential materials, our friendly associates are there to assist you in calculating the right quantities. Visit your nearest SiteOne today or request support online.