How we calculate
Our goal is simple: give you a number you can take to the store or the supplier with confidence. Here is exactly how the calculators work.
Principles
- Every default has a source. If we could not find a published value, we say so and let you enter your own.
- We round up what you buy. Bag counts always round up to whole bags. Volumes are shown to two decimals so you can round to your supplier's increments.
- We show the formula. Each calculator page explains the math with a worked example.
- Everything runs in your browser. Your inputs are not sent to us or stored on a server.
Unit conversions
1 cubic yard = 27 cubic feet = 0.7646 cubic meters. 1 US ton = 2,000 lb. 1 acre = 43,560 square feet. Source: NIST SP 811, Appendix B (unit conversions).
Concrete bag yields
| Bag | Yield (cu ft) |
|---|---|
| 40 lb | 0.3 |
| 50 lb | 0.375 |
| 60 lb | 0.45 |
| 80 lb | 0.6 |
Sources: Quikrete Concrete Mix No. 1101 data sheet (bag yields); Sakrete High-Strength Concrete Mix (bag yields). Manufacturers describe these yields as approximate.
Material weights
| Material | lb per cu ft | lb per cu yd |
|---|---|---|
| Gravel / crushed stone (dry) | 105 | 2,835 |
| Gravel (wet) | 125 | 3,375 |
| Pea gravel | 105 | 2,835 |
| River rock | 105 | 2,835 |
| Sand (dry) | 97 | 2,619 |
| Sand (wet) | 119 | 3,213 |
| Topsoil / loam | 80 | 2,160 |
| Fill dirt (loose, dry) | 76 | 2,052 |
| Fill dirt (loose, moist) | 78 | 2,106 |
| Clay (dry) | 100 | 2,700 |
Source: Engineering ToolBox: densities of dirt, sand and gravel. Real loads vary with rock type, size and moisture. When your supplier quotes a weight, use theirs.
Depth guidance
- Mulch: 2 to 4 inches (Penn State Extension; Clemson HGIC).
- Topsoil for new lawns: at least 4 to 6 inches settled (Penn State Extension).
- Paver base: 6 to 8 inches for patios and walkways, 10 to 14 inches for driveways (Unilock).
Limits
Results are estimates for planning and buying. They do not replace engineering, local building codes or a contractor's site measurements. For structural work, follow your local code and the product manufacturer's instructions.
Corrections
Found an error? Email hello@shedmath.com. We review and fix reported issues and update the review date on the page.