How to use the sandbox sand calculator calculator
- 1
Measure the inside
Measure the inside length and width of a rectangular sandbox, or the inside diameter of a round one. Enter a known area if you already have it.
- 2
Choose the fill depth
Enter the fill depth you have chosen from the sandbox instructions or local guidance, in the depth unit you select.
- 3
Add a bag size or price
Enter a bag volume to see the bag count, and add your own prices to estimate cost.
- 4
Review the result
Read the cubic feet, cubic yards, and bag count, and confirm the amount with your supplier.
Formula
Cubic feet = inside area (sq ft) x fill depth (ft)
Multiply the inside area by the fill depth in feet for cubic feet, or divide square feet times depth in inches by 324 for cubic yards. For bags, divide the cubic feet needed by the bag volume and round up.
Worked example
A rectangular sandbox measures 5 feet by 5 feet inside and will be filled 4 inches deep.
- 1Inside area: 5 x 5 = 25 square feet.
- 2Cubic feet: 25 x (4 / 12) = 8.33 cubic feet.
- 3Cubic yards: 25 x 4 / 324 = 0.31 cubic yards.
- 4With 0.5 cubic foot bags: 8.33 / 0.5 = 16.67, which rounds up to 17 bags.
The sandbox needs about 8.33 cubic feet, which is roughly 0.31 cubic yards or 17 of the 0.5 cubic foot bags.
Worked examples
Round sandbox
A circular sandbox 6 feet across inside, filled 3 inches deep.
- 1Inside area = 3.14159 x (6 / 2)^2 = 28.27 square feet.
- 2Cubic feet: 28.27 x (3 / 12) = 7.07 cubic feet.
- 3Cubic yards: 28.27 x 3 / 324 = 0.26 cubic yards.
The round sandbox needs about 7.07 cubic feet, or roughly 0.26 cubic yards.
Shallower fill
The same 5 by 5 foot sandbox filled 2 inches deep instead of 4.
- 1Inside area: 5 x 5 = 25 square feet.
- 2Cubic feet: 25 x (2 / 12) = 4.17 cubic feet.
- 3Cubic yards: 25 x 2 / 324 = 0.15 cubic yards.
At 2 inches the same sandbox needs about 4.17 cubic feet, roughly half the 4 inch amount.
How to measure a sandbox
Measure the inside of the sandbox, not the outside of the frame, because the walls take up space that will not hold sand. For a rectangular box, measure the inside length and width. For a round box, measure the inside diameter. If the sandbox has an unusual footprint, split it into rectangles and circles and add a section for each.
Keep every measurement in the same units and enter the fill depth you have chosen. The calculator multiplies the inside area by the depth, so an accurate inside measurement is what keeps the estimate right.
Rectangle and circular sandbox calculations
A rectangular sandbox uses inside length times inside width for its area, while a round sandbox uses pi times the radius squared, where the radius is half the inside diameter. Once you have the area, the volume is simply area times fill depth.
Both shapes follow the same volume rule, so you can compare a square and a round box of similar size directly. To review the volume steps in general, see how to calculate cubic yards, and to convert a cubic foot figure use cubic feet to cubic yards.
Bag conversion and bulk planning
Most sandboxes are filled with bagged sand, so entering a bag volume gives you an exact and a whole-bag count. Because you cannot buy part of a bag, round up to the whole number the calculator shows. For larger builds, bulk sand may be an option, and you can add your own prices to compare.
For borders, multiple boxes, or weight estimates, the broader sand calculator handles more shapes and options, and the sand bag calculator focuses on bag counts from an area or a known volume.
Planning for refills and topping up
Sandbox sand is gradually lost to play, wind, and cleanouts, so a box that was full at the start of a season may need topping up later. To estimate a refill, work out the shortfall depth, which is how much lower the sand sits than your target level, and treat that as the fill depth in the calculator.
For example, if a box that holds 4 inches has settled to about 3 inches, you only need to add roughly 1 inch across the inside area, not a full refill. Measuring the current level before you order keeps a top-up from turning into an overbuy.
Common measurement mistakes
These small errors change a sandbox estimate the most:
- Measuring the outside of the frame instead of the inside
- Forgetting that fill depth is usually less than the wall height
- Mixing inches and feet without converting
- Assuming every bag holds the same cubic feet
- Rounding the area before multiplying by the depth
Common Sandbox Footprints to Sand Cubic Yards
Cubic yards for common inside footprints at each fill depth you might choose. Read the inside area on the left and your fill depth across the top.
| Area | 2 in | 3 in | 4 in | 5 in | 6 in |
|---|---|---|---|---|---|
| 9 sq ft | 0.0556 | 0.0833 | 0.111 | 0.139 | 0.167 |
| 16 sq ft | 0.0988 | 0.148 | 0.198 | 0.247 | 0.296 |
| 20 sq ft | 0.123 | 0.185 | 0.247 | 0.309 | 0.37 |
| 25 sq ft | 0.154 | 0.231 | 0.309 | 0.386 | 0.463 |
| 30 sq ft | 0.185 | 0.278 | 0.37 | 0.463 | 0.556 |
| 36 sq ft | 0.222 | 0.333 | 0.444 | 0.556 | 0.667 |
| 49 sq ft | 0.302 | 0.454 | 0.605 | 0.756 | 0.907 |
| 64 sq ft | 0.395 | 0.593 | 0.79 | 0.988 | 1.19 |
Bags per Cubic Yard by Bag Volume
How many bags make one cubic yard, by the cubic feet printed on the bag, with the exact figure and the whole-bag math shown separately.
| Bag volume | Bags per cubic yard | Whole bags for 1 cubic yard |
|---|---|---|
| 0.5 cu ft | 54 | 54 |
| 0.75 cu ft | 36 | 36 |
| 1 cu ft | 27 | 27 |
| 1.5 cu ft | 18 | 18 |
| 2 cu ft | 13.5 | 14 |
| 3 cu ft | 9 | 9 |
Cubic Feet to Cubic Yards for Small Fills
Cubic yards and cubic feet for small volumes, useful for sandbox-sized amounts. One cubic yard is 27 cubic feet.
| Cubic yards | Cubic feet |
|---|---|
| 0.1 | 2.7 |
| 0.15 | 4.05 |
| 0.2 | 5.4 |
| 0.25 | 6.75 |
| 0.3 | 8.1 |
| 0.5 | 13.5 |
| 0.75 | 20.25 |
| 1 | 27 |
Frequently asked questions
- How much sand do I need for a sandbox?
- Measure the inside area, multiply by your chosen fill depth, and convert to cubic feet or a bag count. A 5 by 5 foot box at 4 inches, for example, needs about 8.33 cubic feet.
- Do I measure the inside or the outside of the sandbox?
- Measure the inside, because the frame walls do not hold sand. Using the outside dimensions would overestimate the volume.
- What fill depth should I use for a sandbox?
- There is no single right depth for every sandbox. Use the sandbox manufacturer instructions and applicable local guidance to choose a depth, then enter it in the calculator.
- How many bags of sand for a sandbox?
- Divide the cubic feet needed by the cubic feet on the bag and round up. For a box needing 8.33 cubic feet with 0.5 cubic foot bags, that is 17 bags.
- How do I calculate sand for a round sandbox?
- Use pi times the radius squared for the inside area, where the radius is half the inside diameter, then multiply by the fill depth. The calculator does this when you pick the circle shape.
Sandbox volume uses inside area times fill depth, with 27 cubic feet per cubic yard and 324 square feet per cubic yard inch. Fill depth is chosen by you from the product instructions and local guidance, never prescribed here. Bag counts round up. See the YardCalc calculation methodology.
Results are planning estimates. Last reviewed 2026-07-07.