Hole Volume Calculator
Find the volume of a round or rectangular hole for digging, concrete, or backfill, with a multiplier for many holes.
🕳️ What is the Hole Volume Calculator?
The hole volume calculator works out how much space a hole takes up, which tells you how much soil you will dig out or how much concrete you will pour in. Choose a round or rectangular hole, enter the dimensions, and it returns the total volume in cubic metres, litres, cubic feet, and US gallons. A hole count multiplies the result so you can size a whole fence line or footing grid at once.
This is one of the most common estimating tasks in construction and landscaping. A fence installer needs the concrete for a line of post holes. A deck builder sizes footing holes for the frost line. A gardener digging a pond or planting pit wants the soil volume to remove. A groundworker pricing an excavation quotes in cubic metres. In each case the underlying question is identical: what is the volume of this hole, and of all of them together.
A round hole is treated as a cylinder, so its volume is pi times the radius squared times the depth. Because holes are usually dug to a stated diameter, the calculator halves it to the radius for you. A rectangular hole is a simple box: length times width times depth. A frequent mistake is forgetting that loosened soil bulks up by 20 to 30 percent once excavated, so the pile you cart away is larger than the in-ground volume the calculator reports. For concrete, the hole volume is a close upper bound on what you need, minus the small space the post itself occupies.
The tool is useful because it merges the geometry, the unit conversions, and the multiple-hole arithmetic into one instant answer, with the working shown so you can check it or adjust for over-dig and bulking.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 - Four round fence-post holes
Example 2 - Rectangular footing pit
Example 3 - One round hole in feet
❓ Frequently Asked Questions
🔗 Related Calculators
How do you calculate the volume of a hole?
For a round hole, Volume = pi x radius squared x depth, where the radius is half the diameter. For a rectangular hole, Volume = length x width x depth. Multiply by the number of holes for a total. A 0.3 m diameter hole dug 1 m deep has a volume of pi x 0.15 squared x 1 = 0.0707 cubic metres.
How much concrete do I need for a post hole?
The concrete needed roughly equals the hole volume minus the volume of the post sitting in it. For a 0.3 m diameter hole 1 m deep, the hole is about 0.071 cubic metres. If the post occupies a small fraction, order close to the full hole volume, and add a little extra for spillage and uneven sides.
How do I calculate excavation volume in cubic metres?
Measure the length, width, and depth of the excavation in metres and multiply them together: Volume = length x width x depth. A pit 2 m long, 1.5 m wide, and 1 m deep is 3 cubic metres. For a round pit, use pi x radius squared x depth instead.
How many cubic metres is a cubic yard?
One cubic yard equals about 0.7646 cubic metres, and one cubic metre equals about 1.308 cubic yards. Excavation and concrete are often priced per cubic yard in the US, so convert the calculator's cubic-metre result by multiplying by 1.308 to get cubic yards.
How do I work out the volume of many post holes?
Calculate the volume of one hole, then multiply by the number of holes. This calculator does that automatically when you set the hole count. For 4 holes of 0.071 cubic metres each, the total is about 0.283 cubic metres, or 283 litres of digging or concrete.
Does the soil volume change after digging?
Yes. Soil bulks up when excavated because it loosens and traps air. The loose spoil is typically 20 to 30 percent larger than the in-ground volume. Multiply the calculated hole volume by a bulking factor of about 1.25 to estimate how much loose material you will need to remove or store.
How do I convert hole volume to litres?
Multiply the volume in cubic metres by 1,000. A hole of 0.071 cubic metres equals 71 litres. Litres are handy when comparing against bagged products or when a small hole's cubic-metre figure is an awkward decimal.
What shape should I choose for a round versus square hole?
Use the round mode for auger-dug or cylindrical holes such as fence-post and deck-footing holes. Use the rectangular mode for trenches, pits, and square footings dug with a spade or excavator bucket. Pick whichever matches the cross-section you actually dug.
How accurate is the hole volume estimate?
The formulas are exact for a clean cylinder or rectangular box. Real holes have sloping or irregular sides, so the true volume is usually a little larger than the nominal figure. For ordering concrete or estimating spoil, add a small allowance of 5 to 10 percent for over-dig.
What is the volume of a 12-inch diameter hole 4 feet deep?
A 12-inch (0.3048 m) diameter hole has a radius of 0.1524 m. Dug 4 feet (1.2192 m) deep, the volume is pi x 0.1524 squared x 1.2192 = 0.089 cubic metres, about 89 litres or 3.14 cubic feet. That is roughly the concrete needed for one deck footing before subtracting the post.