Window Well Gravel Calculator (Semi-Circle & Rectangular)
Enter your own custom window well dimensions below—in inches, feet, or centimeters—to calculate exact cubic feet, stone weight, filter fabric size, and 50-lb gravel bags needed.
Measure straight across where the well attaches to your house wall.
Distance from the house wall outward to the front edge of the well.
Total wells to fill
50 lb, 40 lb, or 60 lb
Local store price
At 4 bags (about 155 lbs), you can easily load these into a car trunk or SUV at Home Depot, Lowe’s, or Menards without paying bulk dump-truck delivery fees.
How Much Gravel in a Window Well? (Bag & Volume Chart)
If you are wondering how much gravel for window well installations you need to pick up, a standard curved basement window well (37″ wide × 16″ projection) requires 1.61 cubic feet of stone—which equals four 50-lb bags at a 6-inch depth. Whether you are digging out an older gravel window well or sizing a new pit with our window well rock calculator, this table gives you instant figures for the most common residential and egress window well gravel calculator sizes.
| Window Well Size (Width × Projection) | Well Shape | Gravel at 4″ Depth | Gravel at 6″ Depth (Standard) | Gravel at 8″ Depth (Clay / Deep) |
|---|---|---|---|---|
| Small Basement Well (37″ × 12″) | Semi-Circle | 0.81 cu ft (2 bags / 78 lbs) |
1.21 cu ft (3 bags / 116 lbs) |
1.61 cu ft (4 bags / 155 lbs) |
| Standard Basement Well (37″ × 16″) | Semi-Circle | 1.08 cu ft (3 bags / 103 lbs) |
1.61 cu ft (4 bags / 155 lbs) |
2.15 cu ft (5 bags / 207 lbs) |
| Wide Shallow Well (42″ × 16″) | Semi-Circle | 1.22 cu ft (3 bags / 117 lbs) |
1.83 cu ft (4 bags / 176 lbs) |
2.44 cu ft (5 bags / 235 lbs) |
| Deep Utility Well (42″ × 24″) | Semi-Circle | 1.83 cu ft (4 bags / 176 lbs) |
2.75 cu ft (6 bags / 264 lbs) |
3.67 cu ft (8 bags / 352 lbs) |
| Standard Code Egress Well (48″ × 36″) | Rectangular | 4.00 cu ft (8 bags / 384 lbs) |
6.00 cu ft (12 bags / 576 lbs) |
8.00 cu ft (16 bags / 768 lbs) |
| Large Walkout Egress Well (60″ × 36″) | Rectangular | 5.00 cu ft (10 bags / 480 lbs) |
7.50 cu ft (15 bags / 720 lbs) |
10.00 cu ft (20 bags / 960 lbs) |
How Deep Should Gravel Be in a Window Well?
Homeowners often ask how deep should gravel be in window well pits to stop rainwater from leaking through basement windows. If you are checking how deep should the gravel be in a window well or how deep gravel in window well basins should sit over a drain pipe, use these field-tested guidelines:
You should put 4 to 6 inches of gravel in a standard basement window well. If your house sits on slow-draining clay soil or your window well contains a vertical weeping tile drain pipe, increase the window well gravel depth to between 8 and 12 inches.
Always maintain a window well gravel height that sits at least 2 to 4 inches below the bottom of your window sill so heavy rain cannot splash against the glass or rot the frame.
How Many Inches of Gravel in a Basement Window Well by Soil Type?
Sandy or Loam Soil
Sandy soil absorbs rainwater fast. A 4 to 6 inch bed of pea gravel for window wells prevents mud splashback and keeps damp dirt off your window frame.
Heavy Clay Soil
Clay swells when wet and drains slowly. Pouring 8 to 10 inches of rock creates an underground holding basin so storm water stays below your window sill.
Weeping Tile Drain Pipe
When a vertical 4″ PVC drain pipe connects your well to the footing drain, pour 10 to 12 inches of washed stone over the grate to filter out leaves and mud.
The 3-Inch Window Sill Clearance Rule
Knowing how many inches of gravel in basement window well pits to pour is only half the job—never fill gravel flush with your window frame.
- 2″ to 4″ Sill Gap: Keeps wet stones away from wood, vinyl, or steel window frames.
- Geotextile Filter Cloth: Separates dirt from clean stone so earthworms and mud don’t clog the voids.
- 40% Open Void Space: Stores cloudburst rainwater safely below glass level.
Best Rocks in a Window Well: Pea Gravel vs. Crushed Stone
Picking the right window well gravel size keeps water moving away from your foundation. Using our window well drainage rock estimator above, you can switch between the three best materials for gravel in window wells for drainage:
Pea Gravel (3/8″ to 1/2″)
Putting pea gravel in window well basins is the most popular residential choice. Rounded stones are easy to scoop, level, and step on barefoot during an emergency basement egress escape.
#57 Crushed Stone (3/4″)
Angular washed limestone or granite. Because the sharp edges lock together without compacting, #57 stone offers maximum void space for heavy storm drainage over clay soil.
Washed River Rock (1″ to 2″)
Larger smooth river stones. Many contractors pour 4 inches of pea gravel on the bottom and cap it with 2 inches of river rock so leaf blowers won’t scatter the stones.
How to Calculate & Put Gravel in Window Wells for Drainage
Want to check the math behind our semi circle gravel calculator and gravel calculator window well tool? Convert your measurements from inches to feet (divide inches by 12) and use these formulas:
5 Steps to Install or Replace Window Well Gravel
Frequently Asked Questions About Window Well Gravel
Fast, practical answers for sizing, buying, and maintaining gravel in window well drainage systems: