Outdoor Shower Calculator
— How Much Do You Need?

Gravel is the go-to material for drainage beneath an outdoor shower, and getting this layer right makes a big difference in how well the setup holds up. Excavating the shower footprint to a depth of 6 to 12 inches and filling with clean crushed stone is common. Angular crushed stone, such as #57 stone, works well because the irregular edges lock together, creating a stable and permeable base that channels water away from the surface. For the top layer you stand on, use pea gravel. It is small, rounded, and drains quickly, making a comfortable walking surface. A typical setup layers crushed stone on the bottom for drainage, with a couple of inches of pea gravel on top for comfort. If your soil drains poorly or you expect high use, consider extending the gravel bed outward to give water more area to disperse. The Hello Gravel calculator can help you estimate material needs based on your exact dimensions.

Pea gravel is the most popular choice for outdoor shower floors. It is small, around 3/8 inch, rounded, and smooth enough to walk on barefoot. It drains well, dries quickly, and looks natural with wood or stone surroundings. For the drainage base, use angular crushed stone like #57. The best result is to have crushed stone underneath and pea gravel on top, typically 2 to 3 inches of pea gravel on the walking surface.

For most outdoor showers, a drainage bed of 6 to 12 inches works well. The right depth for your project depends largely on how well your native soil drains on its own. Sandy or loamy soil that already moves water quickly may only need 6 inches of crushed stone beneath the shower area. Dense clay soil that holds water and drains slowly will benefit from going deeper, often 10 to 12 inches or more, so the gravel bed has enough capacity to handle the water load without becoming saturated. Beyond soil type, think about how often the shower will be used. A rinse-off shower used a few times a week after yard work has a much lighter drainage load than a primary outdoor shower used by multiple family members every day. Higher use calls for more drainage depth and sometimes a wider footprint. If you are building in a low spot or an area where water tends to collect naturally, consider extending the gravel bed outward several feet beyond the shower itself to spread the water over a larger absorption area. This can make a big difference in preventing soggy spots and standing water near your shower. Use the Hello Gravel calculator to estimate material quantities once you have settled on your depth and footprint dimensions.

The total amount of gravel you need comes down to the size of your shower footprint, how deep you go with the drainage bed, and whether you are adding a separate surface layer of pea gravel on top. As a practical example, a 6x6 foot drainage area at 6 inches of depth requires roughly 0.7 cubic yards of crushed stone. At 12 inches of depth, that same footprint needs about 1.3 cubic yards. If you are topping the drainage bed with 3 inches of pea gravel across that same 6x6-foot area, add about 0.3 cubic yards or so to your total. That puts a typical single outdoor shower project somewhere in the range of 1 to 1.5 cubic yards of aggregate in total, depending on depth and surface coverage. Keep in mind that many homeowners combine their outdoor shower project with nearby landscaping work, such as a gravel path, a garden border, or a patio base, so you can make full use of your delivery. If you are ordering materials for multiple areas at once, the Hello Gravel calculator lets you add up all your dimensions and get a combined estimate so you only need one delivery. Enter your measurements and it will do the math for you.

In many residential settings, a well-built gravel bed does the job on its own without a formal drain. When you excavate the shower area and fill it with clean crushed stone, you are creating a permeable reservoir that absorbs water and moves it gradually into the surrounding soil. For a shower used a few times a week in a yard with reasonably good drainage, this is often all you need. That said, there are situations where a gravel bed alone is not enough. Heavy clay soil that drains slowly can become saturated over time, especially if the shower is used daily or in a high-rainfall area. In those cases, connecting to a French drain or extending the bed further into your yard can help move water farther away from the shower. It is also worth checking your local building codes before you finalize your drainage plan. Some municipalities regulate where outdoor shower water can be directed. A gravel drainage bed is a solid foundation for any outdoor shower plan, but your site conditions and local rules may shape what else is needed.