Hole Volume Calculator
Volume of a drilled or augered hole from diameter and depth — for drilling, footings, fence and deck posts, and boreholes. Get cubic feet, cubic yards, gallons, and litres, then estimate concrete, gravel, water fill, and excavated spoil.
Hole volume
Enter the hole diameter and depth. Add more than one hole and an overbreak allowance for real-world soil conditions.
Assumes a straight cylindrical hole. Real augered holes run 5–15% oversize in soil — the overbreak allowance above covers washout and belling. Use 0% for cored or cased holes.
Fill estimator
How much material to fill the holes above. Bag yields are nominal — check your bag label.
Bags always round up — you cannot buy part of a bag. Setting fence posts? Post depth, frost line, and spacing are covered by our fence post size calculator.
Spoil estimator
Excavated soil swells — the spoil pile is bigger than the hole. Typical swell: sand & gravel ~15%, clay ~25%, fractured rock ~50%. Adjust to your soil report.
Quick table: volume per foot of depth
Theoretical cylindrical volume for common hole diameters.
| Diameter | Gallons / ft | Cubic feet / ft |
|---|
Frequently asked questions
How do you calculate the volume of a hole?
Treat the hole as a cylinder: volume = pi x radius squared x depth. Measure the diameter, halve it for the radius, and keep the units consistent. Example: an 8-inch-diameter hole 3 feet deep has radius 4 inches, so pi x 16 x 36 inches = 1,809.6 cubic inches, which is 1.0472 cubic feet (7.83 US gallons). The calculator above does this instantly in imperial and metric units.
How many gallons does a 6-inch-diameter hole hold per foot of depth?
A 6-inch-diameter hole holds 1.4688 US gallons per foot of depth (about 1.47 gallons). The quick table below lists gallons per foot for common diameters from 4 to 12 inches. Note this is the same cylinder math as a 6-inch well casing, which is why drillers and well owners get the same per-foot figure.
How much concrete do I need to fill a round hole?
Compute the hole volume, add a waste allowance (10% is typical), then divide by the nominal bag yield: 0.60 cubic feet per 80-lb bag or 0.45 cubic feet per 60-lb bag (check your bag label, yields vary by brand). Example: a 12-inch-diameter hole 4 feet deep is 3.1416 cubic feet (0.1164 cubic yards), needing 6 eighty-pound bags or 8 sixty-pound bags at 10% waste. For slabs, footings, and other non-cylindrical pours, use our concrete calculator instead.
How is hole volume used in drilling?
In drilling, borehole volume is the starting point for job planning: it sizes the drilling-fluid (mud) volume needed to fill the hole, the cement slurry volume for grouting or abandonment, and the gravel-pack volume around a screen. Drillers also compare theoretical hole volume against actual material used — a big gap signals overbreak, washout zones, or lost circulation that needs attention.
Why did my hole take more concrete or gravel than calculated?
Real holes are rarely perfect cylinders. Augers bell out the top, loose soils cave and wash out, and rock drilling leaves an irregular wall — 5 to 15% overbreak is common in soil. That is why the calculator includes an overbreak allowance: set 10% for typical augered holes in soil, more for cobbles or fractured rock, and near 0% for cored or cased holes.
What is the difference between hole volume and well volume?
Hole volume is the geometric volume of the drilled void itself — used to estimate fill material like concrete, gravel, or drilling mud. Well volume is about the water standing inside a finished well: casing water gallons, purge volumes for sampling, and shock-chlorination dosing. If you own a water well and need gallons in the casing, use our well volume calculator.
How do I calculate hole volume in metric units?
Use the same cylinder formula with metric inputs: volume = pi x (diameter/2) squared x depth. Example: a 150 mm diameter hole 1 metre deep is 17.671 litres (0.01767 cubic metres). The calculator accepts millimetres or centimetres for diameter and metres or centimetres for depth, and converts to litres, cubic metres, gallons, and cubic feet automatically.
How many cubic yards are in a 12-inch-diameter hole 4 feet deep?
A 12-inch-diameter hole 4 feet deep holds 3.1416 cubic feet, which is 0.1164 cubic yards — about 6 eighty-pound bags of concrete at 10% waste. This is the classic sonotube footing size, and the quick table below gives the per-foot figures so you can scale to any depth.
Free tool by NRTechStudio