Sandbox Sand Calculator
Enter your sandbox shape and dimensions to find out exactly how much sand you need. Choose a child age group to apply the recommended fill depth automatically, or type your own depth. Results show the sand volume in cubic feet and cubic yards, the weight in pounds and kilograms, and how many standard 50-lb bags to buy. Switch between metric and imperial units at any time.
Formula
Worked example
A rectangular sandbox 6 ft long by 4 ft wide, filled 5 inches deep for preschoolers: area = 6 x 4 = 24 ft^2. Depth in feet = 5/12 = 0.417 ft. Volume = 24 x 0.417 = 10 ft^3. Weight = 10 x 100 = 1,000 lb. Bags = ceil(1,000 / 50) = 20 bags.
How to use this sandbox calculator
Select your unit system (imperial or metric), then choose the sandbox shape. For a rectangular or square sandbox, enter the length and width in feet or metres. For a circular sandbox, enter the diameter. Next, pick the child age group that best describes who will be using the sandbox - the calculator will fill in the recommended depth automatically. If you want a specific depth, choose "Custom depth" and type it in. The results update instantly as you type, showing you the sand volume in cubic feet and cubic yards, the total weight in pounds and kilograms, and how many standard 50-lb bags to buy. If you enter a price per bag, you also get an estimated material cost.
How the calculation works
For a rectangular sandbox, the volume is simply length times width times depth. For a circular sandbox, the area is pi times the radius squared, then multiplied by depth. The weight is volume times the bulk density of play sand, which is about 100 lb per cubic foot (1,600 kg/m3). The bag count divides that weight by 50 lb and rounds up to the nearest whole bag. Bag sizes vary by brand; if yours differ, divide the total weight by the actual bag weight and round up.
Choosing the right sand depth
The recommended depth varies by age because older children dig more vigorously and need deeper sand to stay safe. Infant sandboxes typically use only 2.5 inches of sand, enough for sensory exploration without the risk of burial. Toddlers benefit from 3 inches. Preschoolers, who build castles and dig tunnels, need 5 inches. Gradeschoolers are best served by 9 inches, which gives enough depth for active excavation projects. If the sandbox doubles as a fall-impact surface under a small play structure, check local playground safety standards, which often require 9 to 12 inches of loose fill material.
Sand type and safety tips
Always use play sand specifically labelled as non-toxic for children. Avoid construction sand and general-purpose sand, which can contain elevated levels of crystalline silica, a respiratory hazard. Washed, kiln-dried play sand is the safest option and drains quickly after rain. Add 5 to 10 percent extra beyond the calculated amount to account for settling over time and sand lost during play. Replace or top up the sand at least once a year, cover the sandbox when not in use to keep it clean, and rake it regularly to maintain hygiene.
Recommended sand depth by child age
| Age group | Recommended depth (in) | Recommended depth (cm) | Notes |
|---|---|---|---|
| Infant (1-2 years) | 2.5 | 6.4 | Supervised sensory play only |
| Toddler (2-3 years) | 3 | 7.6 | Supervised digging and scooping |
| Preschooler (3-5 years) | 5 | 12.7 | Active play, castle building |
| Gradeschooler (5-12 years) | 9 | 22.9 | Deep digging and active projects |
Depth guidelines from child play-safety research. Use deeper fill for older children who dig more actively.
Frequently asked questions
How many bags of sand do I need for a 6x4 sandbox?
A 6 ft by 4 ft rectangular sandbox filled to the preschooler recommendation of 5 inches deep needs about 10 cubic feet of sand, which weighs around 1,000 lb. That is 20 standard 50-lb bags. At a typical retail price of $6 to $10 per bag, expect to spend $120 to $200 on sand.
How deep should I fill a sandbox with sand?
The recommended depth depends on who will be using it. For infants (1-2 years), 2.5 inches is enough. Toddlers (2-3 years) benefit from 3 inches. Preschoolers (3-5 years) need at least 5 inches for active play, and gradeschoolers (5-12 years) enjoy 9 inches for deep digging. If the sandbox also serves as a fall surface under play equipment, local safety codes often require 9 to 12 inches.
What type of sand is safest for a children's sandbox?
Look for play sand that is specifically labelled as washed and non-toxic. Kiln-dried play sand is free of silica dust and bacteria, drains quickly, and stays loose. Avoid construction sand, concrete sand, and beach sand, which can contain higher levels of crystalline silica or contaminants.
How do I convert cubic feet of sand to bags?
A standard 50-lb bag of play sand covers about 0.5 cubic feet at a depth of about 1 inch (dense coverage). However, the most reliable method is weight-based: multiply your cubic footage by 100 (the approximate density of sand in lb/ft3) to get the total weight in pounds, then divide by 50 and round up. This calculator does all of that for you automatically.
How much does it cost to fill a sandbox with sand?
Retail play sand typically costs $6 to $12 per 50-lb bag, so a small sandbox needing 10-15 bags costs about $60 to $180. Larger sandboxes that need a cubic yard or more of sand are often cheaper to fill by buying bulk sand from a landscaping supplier, where prices can drop to $25 to $50 per cubic yard. Enter your bag price in this calculator to get an instant cost estimate.