Drainage Stone Calculator
Calculate the right amount of stone for effective drainage systems.
Quick Answer
For drainage, use clean angular stone such as #57. Multiply trench length × width × depth in feet, divide by 27 for cubic yards, then multiply by about 1.5 for tons. A 50 ft trench 1 ft wide and 1 ft deep needs about 1.85 cubic yards (roughly 2.8 tons).
Drainage Stone Calculator — French Drain Gravel Guide
Proper water management is key to protecting your home's foundation and maintaining a healthy landscape. Our drainage stone calculator helps you estimate the amount of clean gravel or crushed stone needed for projects like French drains, dry wells, or backfilling behind retaining walls.
The key to good drainage is using a 'clean' stone—one that has been washed to remove fine particles and dust. This creates voids between the stones, allowing water to percolate through freely. This calculator is the perfect tool for ensuring your drainage system has the capacity it needs to be effective.
What Keeps a Stone Drain Working for Years
Clean stone drains beautifully on day one — the problem is silt. Over time, fine soil migrates into the voids between stones and slowly chokes off the water flow you built the system for. Wrapping the stone in a geotextile separation fabric is the fix: it lets water pass but keeps soil out, so the drain stays open for years instead of clogging. A bow rake makes spreading and grading the stone to an even depth quick work, so water moves where you want it.
Geotextile Separation Fabric
Lets water through but keeps silt out, so the stone voids don't clog over time.
Check Price on AmazonBow Rake
Spreads and grades drainage stone to an even depth so water flows where intended.
Check Price on AmazonThe product links above are affiliate links — at no extra cost to you.
Frequently Asked Questions
What is the best stone for a French drain?
The ideal stone for a French drain is clean, uniformly sized crushed stone or gravel, typically in the 3/4 inch to 1.5-inch range. #57 crushed stone is a very common and effective choice.
How much stone do I need for a French drain?
A typical French drain trench is 1 foot wide and 1.5 feet deep. For every 10 feet of length, you would need about 0.56 cubic yards of stone. Use our stone calculator for French drain with your exact trench dimensions for a precise number.
Do I need to wrap my French drain pipe?
Yes, the perforated drain pipe should be wrapped in a geotextile filter fabric 'sleeve' to prevent silt and soil from clogging the pipe's holes.
What does 'clean' stone mean?
'Clean' or 'washed' stone means the aggregate has been rinsed to remove fine particles, sand, and dust. This is essential for drainage applications, as the fines would otherwise clog the spaces between the stones and impede water flow. Clean stone maintains its drainage capacity over time, preventing system failure.
How deep should a French drain be?
The depth depends on what you are trying to achieve. For surface water, 18-24 inches is common. To drain groundwater away from a foundation, the drain must be at least as deep as the foundation's footing.
Can I use pea gravel for drainage?
While pea gravel allows water flow, its rounded shape is not ideal for locking in place. An angular crushed stone provides more stability and is generally preferred for drainage systems around foundations and retaining walls.