Gravel Sizes, Types & Uses — A Simple Guide for Homeowners & Contractors
Become an expert in 10 minutes. Whether you're building a driveway, retaining wall, French drain, or a landscape bed — choosing the right gravel size and type is the difference between a strong, long-lasting project and one that fails fast.
💬 At Terrain Bound, we get a lot of questions about gravel: What size do I need? What do these numbers mean? What’s best for drainage?
This guide is here to make it crystal clear. We'll walk you through gravel sizing, real-world uses, material types, and how to layer it properly for lasting results.
🛑 And just a quick note: There’s more than one way to do great work. This is what we’ve found to be reliable, consistent, and contractor-approved through years of experience here in Colorado. But we know every builder has their own approach — and that’s what makes the trades so dynamic.
⚙️ Understanding Gravel Sizes (And the Numbering System)
Gravel is categorized by a number system that refers to the diameter range of the stone. The lower the number, the larger the gravel.
Gravel GradeSize (inches)Common Uses#12" – 4"Heavy drainage, erosion control#3½" – 2"Base for driveways, retaining walls#4¾" – 1½"Patios, walkways, landscape beds#5½" – 1"Driveways, walkways, concrete mix#57½" – ¾"Middle layer in driveways, French drains, backfill#8⅜" – ½"Top layer for walkways, backfill#10 (Stone Dust)<⅜"Paver base, final surfacing#89~⅜"Decorative gravel, pipe fill, retaining wall backfill
🔁 Do You Need More Than One Gravel Size?
Most well-built gravel installations require multiple layers of stone in different sizes:
✅ 1. Base Layer
Use large gravel like #3 or #4
Creates a stable foundation with excellent drainage
Ideal for: Driveways, retaining walls, French drains
✅ 2. Middle Layer
Use medium gravel like #57
Helps stabilize the top and maintain drainage
Ideal for: Driveway builds, patio foundations, backfill
✅ 3. Top Layer
Use smaller gravel like #8, #89, or stone dust
Provides a smooth, finished surface
Ideal for: Walkways, decorative beds, patios
🪨 Gravel Material Types: Not All Stone Is Created Equal
The type of stone matters just as much as the size. Here are the most common gravel materials used in exterior projects:
1. Crushed Stone
What it is: Mined stone (usually granite or limestone) crushed mechanically
Why it works: Sharp, angular edges compact and lock together
Best for: Driveways, retaining walls, French drains, patios, base layers
2. Pea Gravel (Similar to #89)
What it is: Naturally rounded stones, usually ⅜" in size
Why it works: Smooth and decorative
Best for: Garden beds, walkways, pipe fill
Not great for: Structural base — tends to shift under weight
3. Decomposed Granite
What it is: Crushed granite that’s almost a mix of gravel and sand
Why it works: Compacts tightly and has a natural appearance
Best for: Pathways, patios, xeriscaping
4. River Rock
What it is: Smooth, rounded stones in 1–3" diameter
Why it works: Visually appealing for dry creek beds and erosion control
Best for: Decorative drainage zones
Not great for: High traffic areas — easily shifts and can be slippery
5. Lava Rock
What it is: Lightweight volcanic stone
Why it works: Porous and excellent for drainage
Best for: Garden beds, mulch replacement
Downsides: Costly and prone to scattering
🔍 How to Choose the Right Gravel for Each Project
Here’s a simplified breakdown by use case:
ProjectRecommended Gravel SizesMaterial TypeDrivewayBase: #3 or #4 / Top: #57 or #8Crushed stone (granite/limestone)French DrainBase: #3 or #4 / Fill: #57Crushed stoneWalkwayBase: #4 / Top: #8 or Decomposed GraniteCrushed granite, pea gravelPatioBase: #4 / Top: Stone dust or #57Crushed limestoneRetaining Wall BackfillFill: #57 or #89Crushed stoneLandscape BedsTop: Pea gravel or River RockDecorative gravel
💰 Cost & Coverage: What to Expect
Gravel is usually sold by the ton or cubic yard. Here's a quick cheat sheet:
1 ton covers ~80–100 sq ft at 2" depth
1 cubic yard ≈ 1.4 tons
Cost Estimates by Material:
TypeTypical Price Per TonCrusher Run$20 – $35Pea Gravel$30 – $65Decomposed Granite$35 – $75River Rock$45 – $130Lava Rock$80 – $200
Pro Tip: Always factor in delivery, grading, and compaction costs for a realistic total.
🛠️ Final Word: Layer Like a Pro, Stay Open to Learning
Gravel isn’t one-size-fits-all. Soil conditions, climate, project goals, and even personal preference can shape how you build.
What we’ve laid out above is a proven, reliable system — but it’s not the only one. We believe in building with integrity, being open to collaboration, and always keeping the door open for new ideas or improved techniques.
👷♂️ Contractors: If you’ve got a method you swear by, we’d love to hear it.
🏡 Homeowners: If you're ever unsure, we’re happy to walk your project with you and figure out the best path forward.
Need help deciding what gravel’s right for your job?
At Terrain Bound, we help homeowners and builders across Colorado get it right the first time — with clean installs, clear advice, and long-lasting results.
