How Much Topsoil Do I Need? Easy Calculator & Guide
Whether you're starting a new lawn, planting a vegetable garden, or filling raised beds, the wrong amount of topsoil can sink your entire project. Too little and your plants won't have enough nutrients to thrive. Too much and you're wasting money. But how much do you actually need?
The good news: figuring it out is easier than you think. You don't need to guess, and you don't need a degree in landscaping. In this guide, we'll walk you through exactly how much topsoil you need—plus a simple formula (or calculator) to do the math for you.
What is Topsoil, Anyway?
Topsoil is the nutrient-rich upper layer of soil that plants actually want to grow in. It's darker, looser, and packed with organic matter—unlike the dense subsoil underneath. When you order topsoil for delivery, you're getting the good stuff that makes gardens and lawns thrive.
How Much Topsoil Do You Need? The Formula
Here's the basic formula:
Length (ft) × Width (ft) × Depth (inches) ÷ 324 = Cubic Yards
Wait, where did 324 come from? Here's the math:
- 1 cubic yard = 27 cubic feet
- 27 cubic feet × 12 inches per foot = 324 cubic inches per cubic yard
Example 1: Lawn Area
You want to spread topsoil across a 20' × 30' lawn, 2 inches deep.
20 × 30 × 2 ÷ 324 = 3.7 cubic yards
You'd order 4 cubic yards (accounts for settling).
Example 2: Raised Beds
You have a 4' × 8' raised bed, and you want to fill it 12 inches deep.
4 × 8 × 12 ÷ 324 = 1.18 cubic yards
You'd order about 1.5 cubic yards (accounts for settling).
Example 3: Multiple Areas
You're doing:
- 500 sq ft lawn at 2" deep = 3.1 cy
- 3 raised beds (4×8 each) at 12" deep = 3.5 cy
- 100 sq ft flower bed at 4" deep = 1.2 cy
Total = 7.8 cubic yards → order 8 cy
How Deep Should Your Topsoil Be?
It depends on what you're growing:
| Project | Depth | Why |
|---|---|---|
| Lawn seeding | 2-3" | Enough for grass roots to establish |
| Lawn renovation | 3-4" | Covers uneven ground |
| Flower beds | 4-6" | Deep for shrubs and perennials |
| Vegetable gardens | 8-12" | Deep for root vegetables |
| Raised beds | 10-12" | Full depth needed |
| Trees & shrubs | 12"+ | Deepest rooting needs |
Raised Bed Topsoil Quick Reference
Can't do math in your head? Use this quick reference:
| Bed Size | 8" Deep | 10" Deep | 12" Deep |
|---|---|---|---|
| 2×4 | 0.24 cy | 0.3 cy | 0.36 cy |
| 4×4 | 0.48 cy | 0.6 cy | 0.73 cy |
| 4×8 | 0.97 cy | 1.2 cy | 1.46 cy |
| 4×12 | 1.45 cy | 1.8 cy | 2.2 cy |
Round up 0.5+ to next whole number
Real-World Tips
- Always round up. Soil settles, and you'd rather have extra than run short.
- Account for settling. New topsoil typically settles 10-15% in the first season.
- Mix if you can. Topsoil + compost (50/50 or 60/40) is even better than pure topsoil.
- Don't skimp on depth. Thin topsoil means shallow roots, which means stressed plants.
Harbor Soils Topsoil Delivery
If you're in Gig Harbor, Port Orchard, Silverdale, Bremerton, Purdy, Artondale, or Olalla, you can order bulk topsoil delivery with no minimums and same-day service.
Use our topsoil calculator above, then call 253-857-5125 to order. We'll deliver exactly what you need.
Last updated: March 5, 2026