Soil Calculator Guide: How to Estimate Topsoil, Mulch, and Fill Dirt
Whether you are building a raised garden bed, laying a new lawn, or filling a foundation, knowing how much soil to order can save hundreds of dollars. Too little means a second delivery charge; too much means paying for material you do not need and dealing with excess dirt. This guide covers the calculation formulas, material types, depth recommendations, and delivery considerations for every landscaping project.
February 23, 2026
12 min read
Construction
The Soil Volume Formula
Cubic Yards = (Length ft × Width ft × Depth ft) ÷ 27
Always convert inches to feet first: divide inches by 12. For example, 6 inches = 0.5 feet.
Quick Reference Examples
| Area (sq ft) | 2" Deep | 4" Deep | 6" Deep | 12" Deep |
|---|---|---|---|---|
| 100 | 0.6 yd³ | 1.2 yd³ | 1.9 yd³ | 3.7 yd³ |
| 250 | 1.5 yd³ | 3.1 yd³ | 4.6 yd³ | 9.3 yd³ |
| 500 | 3.1 yd³ | 6.2 yd³ | 9.3 yd³ | 18.5 yd³ |
| 1000 | 6.2 yd³ | 12.3 yd³ | 18.5 yd³ | 37.0 yd³ |
Recommended Depths by Project
| Project | Material | Depth |
|---|---|---|
| New lawn | Topsoil | 4-6 inches |
| Overseeding | Topsoil/compost mix | 1-2 inches |
| Flower beds | Garden soil | 6-8 inches |
| Vegetable garden | Garden soil + compost | 12+ inches |
| Raised beds | Raised bed mix | 12-18 inches |
| Mulch around trees | Bark/wood mulch | 2-4 inches |
| Pathway gravel | Crushed stone | 2-3 inches |
| Driveway base | Gravel | 4-8 inches |
Material Types and Weights
- Topsoil: 1,800-2,200 lbs/yd³ — General-purpose, good for lawns and gardens
- Garden soil: 1,400-1,600 lbs/yd³ — Enriched with organic matter for planting
- Compost: 800-1,000 lbs/yd³ — Nutrient-rich soil amendment
- Mulch: 400-800 lbs/yd³ — Lightweight, varies by type
- Sand: 2,600-2,800 lbs/yd³ — Heavy, used for drainage and leveling
- Gravel: 2,800-3,000 lbs/yd³ — Driveways, drainage, pathways
- Fill dirt: 2,000-2,500 lbs/yd³ — Inexpensive, for grading and filling
Tip: Most delivery trucks carry 10-15 cubic yards per load. Ordering close to a full truckload is the most cost-effective. Ask your supplier about minimum delivery quantities and per-load pricing.
Irregular Area Calculations
- Circular area: π × radius² × depth (all in feet) ÷ 27
- Triangular area: ½ × base × height × depth ÷ 27
- Complex shapes: Break into rectangles, triangles, and circles; calculate each; sum
- Sloped areas: Average the shallow and deep ends for effective depth
Construction Calculator Tools
Free Calculators:
- Soil Calculator — Estimate soil quantities
- Concrete Calculator — Volume and mix estimates
- Fence Calculator — Post, rail, and material
- Tile Calculator — Tile and grout quantities
- Paint Calculator — Paint coverage estimates
- Percentage Calculator — Add 10% buffer
Frequently Asked Questions
Length × Width × Depth (all in feet) ÷ 27. Add 10% extra for settling and uneven surfaces.
Dry topsoil: ~2,000 lbs/yd³. Compost: ~900 lbs. Mulch: ~600 lbs. Gravel: ~2,900 lbs. Wet soil weighs 30-50% more.
New lawns: 4-6 inches. Overseeding: 1-2 inches. Vegetable gardens: 12+ inches. Raised beds: 12-18 inches.
2-4 inches deep. 1 cubic yard covers ~160 sq ft at 2" or ~108 sq ft at 3". Calculate area × depth ÷ 27.
Related Guides
- Fence Calculator Guide
- Tile Calculator Guide
- Paint Calculator Guide