Planter Box Calculator
— How Much Do You Need?

A planter box needs three things: a drainage layer, a growing medium, and enough material to reach the right depth. Start with a one to two inch layer of pea gravel or coarse gravel for drainage. Above that, use quality topsoil as the main growing medium. You can blend in coarse sand to improve drainage through the soil column. Hello Gravel sells topsoil, pea gravel, and coarse sand in bulk by the truckload. For large projects, use the Hello Gravel calculator to estimate volumes and let the team help you put together the right order.

Place a one to two inch layer of pea gravel or coarse gravel at the bottom. This creates space for excess water to drain away from roots and helps prevent waterlogged soil. Pea gravel is popular for its smooth flow, but other coarse gravels work too. Hello Gravel carries both options in bulk for single boxes or multiple projects.

Overwatering is the top cause of failure in containers. Waterlogged roots with limited oxygen lead to root rot and decline. To prevent this, ensure proper drainage holes and use a growing medium that drains well. A gravel drainage layer plus quality topsoil helps keep roots healthy, and you can mix in coarse sand to improve drainage. Hello Gravel offers topsoil and coarse sand in bulk to support this approach.

Material needs depend on your box dimensions. Multiply length by width by depth to get volume in cubic feet, then divide by 27 to get cubic yards. For example, an 8 by 4 foot box that is 18 inches deep holds about 1.8 cubic yards. Plan for the drainage layer and the topsoil when ordering. Use the Hello Gravel calculator for a precise estimate for your project, and contact the team if you have questions.

A planter box is a fully enclosed container with a sealed base, so all growing medium must come from inside the box. A raised bed sits on the ground with an open bottom that connects to native soil. Because a planter box does not access ground soil, you need a complete growing medium and drainage inside the box. For planters, prioritize topsoil as the main medium, a drainage layer of pea or coarse gravel, and optional coarse sand for drainage. Hello Gravel supplies these materials in bulk.