Quick Answer by Sandbox Size
| Sandbox Size | Depth | Cubic Yards | 50 lb Bags |
|---|---|---|---|
| 4×4 ft (small) | 6 inches | 0.30 yd³ | 16 bags |
| 4×6 ft (medium) | 6 inches | 0.44 yd³ | 24 bags |
| 4×8 ft (standard) | 6 inches | 0.59 yd³ | 32 bags |
| 6×8 ft (large) | 8 inches | 1.19 yd³ | 64 bags |
| 8×8 ft (XL backyard) | 8 inches | 1.58 yd³ | 85 bags |
| Round 48" plastic tub | 4 inches | 0.15 yd³ | 8 bags |
Get Your Exact Bag Count
Enter your sandbox dimensions and get cubic yards, bags, and total weight.
Open Sand Calculator →The Formula
Length (ft) × Width (ft) × Depth (in) ÷ 324 = Cubic Yards
Example: 4×8 ft sandbox at 6 inches deep
- 4 × 8 = 32 sq ft
- 32 × 6 ÷ 324 = 0.59 cubic yards
- 0.59 × 27 = 15.9 cubic feet
- At 0.5 cu ft per 50 lb bag: 32 bags
How Deep Should Sandbox Sand Be?
- 4 inches: Bare minimum — works for small plastic tubs
- 6 inches: Standard for home sandboxes — enough to build and dig
- 8–12 inches: Ideal for larger areas and active play — better fall cushion
- CPSC guideline: For playgrounds, 9 inches of loose sand is recommended for fall protection from 4 ft height
💡 Topping up vs new fill
If refreshing an old sandbox: rake existing sand flat, check the depth. If less than 4 inches, add a fresh layer. Use the formula above for just the top-up depth (e.g., adding 2 inches to bring it back to 6 inches).
What Type of Sand for Sandboxes?
- ✅ Play sand / washed sand — best choice; fine, clean, safe for kids
- ✅ White silica sand — premium option; non-staining, very fine
- ❌ Construction / fill sand — not recommended; may contain clay, silt, or debris
- ❌ Beach sand — contains salt and bacteria; not suitable
- ❌ Paver sand — too coarse, scratchy on skin
Bags vs. Bulk for Sandboxes
| Sandbox Size | Bags (50 lb @ $6) | Bulk (≈ $30/yd³) | Savings |
|---|---|---|---|
| 4×4 ft @ 6" | $96 (16 bags) | Bulk min. applies | Use bags |
| 4×8 ft @ 6" | $192 (32 bags) | ≈ $18 bulk | Bags for convenience |
| 6×8 ft @ 8" | $384 (64 bags) | ≈ $36 bulk | $348 savings — go bulk! |
| 8×8 ft @ 8" | $510 (85 bags) | ≈ $47 bulk | $463 savings — go bulk! |
Rule of thumb: Over 50 bags → bulk is almost always cheaper. Check that your supplier sells play sand in bulk (not all do).
Safety Tips
- Replace sandbox sand every 1–2 years to prevent bacteria buildup
- Use a cover when not in use — keeps cats and pests out
- Line the bottom with landscape fabric for drainage, not plastic
- Check for crystalline silica content — some cheap sands have high levels; look for ASTM C778 certified play sand
Related Guides
- Sand Cubic Yard Calculator
- How Many Yards of Sand Do I Need? — Full sand project guide
- How Much Does a Yard of Sand Weigh?