How much gravel do I need?
The short answer: multiply your area by depth to get volume, then multiply by density to get weight. This guide shows the full working, the depths typical projects use, and the honest caveats — or skip to a tool: the gravel calculator does all of this instantly.
The formula
Volume = Length × Width × Depth
Weight = Volume × Density
Depth is where most estimates go wrong: it has to be in the same units as the rest. Since gravel depth is usually given in inches, divide by 12 first — 3 inches of gravel is 0.25 feet. Then:
- Cubic feet → cubic yards: divide by 27
- Cubic yards → tons: multiply by the material's density (about 1.4–1.5 for most gravel, up to ~1.6 for crusher run)
Worked example: a 20 × 10 ft space at 3 inches deep: 20 × 10 × 0.25 = 50 ft³ → 50 ÷ 27 = 1.85 yd³ → 1.85 × 1.42 ≈ 2.6 tons of gravel.
How deep? It depends on the job
| Project | Typical depth | Why |
|---|---|---|
| Walkway / path | 2–3" | Deep enough to look full over fabric, shallow enough to walk on |
| Landscape bed | 2" | Weed suppression without smothering plant roots |
| Play area | 3–4" | Cushioning; pea gravel is the usual choice |
| Driveway base + top | 4–6" + 2–3" | Two layers: structural base, clean finish |
| Paver base (patio) | 4–6" | Compacted angular stone carries the load |
| French drain trench | trench-sized | Volume is the trench, not the ground above it |
| Aquarium substrate | 1–3" | Tank math in pounds — a different tool entirely |
Common sizes, pre-computed
| Area | 2" deep | 3" deep | 4" deep |
|---|---|---|---|
| 100 ft² (10 × 10) | 0.62 yd³ · 0.9 t | 0.93 yd³ · 1.3 t | 1.23 yd³ · 1.8 t |
| 200 ft² (20 × 10) | 1.23 yd³ · 1.8 t | 1.85 yd³ · 2.6 t | 2.47 yd³ · 3.5 t |
| 400 ft² (20 × 20) | 2.47 yd³ · 3.5 t | 3.70 yd³ · 5.3 t | 4.94 yd³ · 7.0 t |
| 800 ft² (40 × 20) | 4.94 yd³ · 7.0 t | 7.41 yd³ · 10.5 t | 9.88 yd³ · 14.0 t |
| 1,000 ft² (50 × 20) | 6.17 yd³ · 8.8 t | 9.26 yd³ · 13.1 t | 12.35 yd³ · 17.5 t |
When to order extra
Calculators — ours included — return the loose quantity for the exact shape you entered. The real world adds:
- Compaction: crushed bases lose 10–15% of their loose depth under a plate compactor.
- Uneven ground: dips quietly eat more gravel than the plan says.
- Spillage and edging: some material always ends up outside the lines.
- Load rounding: suppliers deliver in practical increments.
Ordering 5–10% over the estimate is the norm for surface gravel; for compacted bases make it 10–15%. For the deeper story on accuracy, read are online gravel calculators accurate?
Tools that do the math for you
- Gravel calculator — any shape, any material, all units at once
- Pea gravel calculator — walkways, beds, play areas
- Gravel driveway calculator — two-layer driveways
- Gravel cost calculator — turn quantity into a price
Last updated: September 20, 2026