How much sand do I need for a sandbox?

The short answer

At 6 inches deep, you need one 50 lb bag of play sand for every square foot of sandbox. A 4 x 4 ft box takes 16 bags, a 5 x 5 ft box 25 and an 8 x 8 ft box

1. The rule comes straight off the bag: Sakrete rates a 50 lb bag of play sand at 6 square feet one inch deep¹, which is half a cubic foot, so the number of bags is the inside area in square feet times the depth in inches, divided by 6.

Six inches is the depth to plan a built box around. Lowe's sandbox plan builds an 8 x 8 ft frame 12 inches deep, works out a volume of 64 cubic feet, and then buys 64 bags, which it says "should fill it about halfway"³. A seller of a 10 x 10 ft kit gives a recommended fill of 6 to 8 inches "to provide adequate play depth while preventing spillover"¹².

Two answers circulate for the same box. Online calculators that say an 8 x 8 needs 128 bags multiply by the wall height, as if the box were filled to the brim. Kit listings that say 12 to 14 bags for a 5 ft box look stingy next to that, but they are right: none of the boxes compared below is designed to be full. Fill to a depth, never to the wall.

Bags of play sand by box size

The table is the formula with every figure rounded up to a whole bag. It is the inside measurement that counts, not the outside of the frame.

Three adjustments cover most boxes that are not in the table:

• 60 lb bags: divide by 7 instead of 6. Sakrete rates its 60 lb bag at 7 square feet one inch deep¹.
• Round boxes: the area is 3.14 times the radius squared. A 6 ft circle is 28.3 square feet, so 29 bags at 6 inches.
• Octagons: the area is about 0.83 times the width squared, measured flat side to flat side. A 6.5 ft octagon is about 35 square feet.

Quikrete's data sheet describes its Premium Play Sand as washed and screened for children's sandboxes and "best used when kept damp"², but gives no yield, so for any other bag, read the coverage printed on it. Whatever the brand, buy sand sold for sandboxes rather than construction sand¹⁴. Why the bag carries a cancer warning, and what to check before you buy, is covered in is play sand safe.

What kit sandboxes actually hold

Every kit maker below gives a sand figure. Spread that sand over the outside footprint and you get the depth the box was designed for. The real depth is a little more, because the walls take up part of the footprint.

The pattern is clear. The ready-made boxes, plastic and wooden, are built around 2.5 to 4 inches of sand, roughly a third of their wall height. A four-bench wooden octagon manual asks for 800 to 1,000 lb¹⁰, the same range. The two that are built or framed on site from lumber, and that you choose the depth for, land at 6 to 8 inches, about half the wall.

Sand tables are smaller again. Step2's Naturally Playful Sand Table holds up to 80 lb and the Crabbie Sand Table 25 lb⁶⁷. If a sand table is what you have, one or two bags is the whole job, and water and sand play covers the play side. For under fives, toddler equipment explains why sand and ground level play carry so much of the play.

The listing that disagrees with itself

The same 10 x 10 ft kit FAQ says the box "holds 5,000 pounds of sand when filled to the recommended depth", that you will need "approximately 83 cubic feet", and that this "translates to about 50 bags of 50-pound play sand"¹². Those are three different boxes:

Fifty bags of 50 lb is 2,500 lb, not 5,000, and only the 5,000 lb figure agrees with the listing's own 6 to 8 inch recommendation. Buy 50 bags and you get 3 inches; order 83 cubic feet and you get 10. Work the number from your own tape measure, not from a listing.

Bags or bulk: cubic yards and tons

Divide cubic feet by 27 for cubic yards. For weight, the bag itself gives the conversion: 50 lb in half a cubic foot is 100 lb per cubic foot, or about 2,700 lb per cubic yard, about 1.35 tons. That sits inside the 2,200 to 2,900 lb range given for sand in how much mulch do I need, which has the delivery and truck detail.

Small boxes are a bag job. By an 8 x 8 box it is 64 bags, over a ton and a half carried by hand, and a bulk quote is worth getting: ask the yard for washed play sand by name and for its weight per cubic yard. The mulch quantity calculator does the same cubic yard conversion for any area.

Childcare and public sand pits run deeper

A licensed centre's sand pit is a different scale. Saskatchewan's centre licensing guidance says "Sand play areas should be turned over to a depth of 460 mm (18 inches) annually"¹³, which assumes a pit at least that deep. The same page doses its sand cleaning by volume: per 175 cubic feet of sand, a 2 gallon watering can with 4 fluid ounces of bleach, hosed in, then the sand turned over "one shovelful (17 cm or 7.5 inches)" before children use it again¹³. Before you can follow that, you need the volume, which is the same arithmetic as the first table.

Replacement is the other recurring order. An insurer's sandbox bulletin notes that "Some organizations recommend replacing all of the sand every one to two years"¹⁴, and the fill number you calculate now is the order you place then. Childcare playgrounds covers the wider licensing picture, and cleaning and sanitizing the routine between replacements.

Where these numbers stop

The bag rule rests on one maker's printed yield, Sakrete's 2010 data sheet, and Lowe's guide uses the same half cubic foot¹³. Another bag size or brand may print a different coverage; when it does, use the bag. The implied kit depths spread each maker's figure over the outside footprint, so treat them as about right rather than exact. Kit figures are the maker's own, often "up to". None of the sources here is a standard that sets a sandbox depth: the 6 inch figure is what the two built-box sources give, not a rule.

What to do next

Measure the inside of the box, not the frame. If it is a kit, buy what the maker says and stop there. If you built it, choose a depth of about 6 inches or half the wall, multiply square feet by inches, divide by 6, and add a couple of bags for the first weeks.

Then put the effort underneath and on top. Sandboxes covers drainage, covers and turning, site prep and leveling and drainage and base layers cover the ground beneath, and if space is tight, small yards shows where a box fits. Add loose parts such as buckets, scoops and water, which is where the sand earns its place.