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Hole Volume Calculator

Construction

Calculate the volume of a cylindrical hole in cubic yards for post holes, footings, or concrete piers. Enter diameter, depth, and quantity to get results.

Reviewed by the thecalcu.com team · Last updated July 12, 2026

260
2120
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Total Volume

0.058
Total Volume (cu ft)
1.57

This calculator computes your Total Volume, Total Volume (cu ft) from the values you enter.

Inputs
Hole DiameterHole DepthNumber of Holes
Outputs
Total VolumeTotal Volume (cu ft)

What is a Hole Volume?

A hole volume calculator determines how much fill material, typically concrete, is needed to fill a cylindrical excavation, such as a fence post hole, deck footing, or column base. Since holes for posts and footings are almost always dug round using an auger or post-hole digger, their volume follows standard cylinder geometry: radius squared, times pi, times depth. Getting this number right before ordering concrete avoids both costly overages and frustrating mid-pour shortages.

This tool takes your hole's diameter and depth in inches, along with the number of holes you're filling, and converts the result into cubic yards, the unit concrete is typically sold and delivered in. It pairs well with the Concrete Calculator for slab and footing work, and the Concrete Tube Estimator for column forms.

Why Use a Hole Volume Calculator?

Fence and deck contractors often need concrete volume for dozens of post holes at once, and manually calculating cylinder volume for each one by hand is slow and error-prone. This calculator handles the geometry instantly and multiplies by quantity, so a 10-post fence line or 6-footing deck project gets an accurate total in seconds.

It's also useful for verifying how many bags of pre-mixed concrete to buy for a small DIY project, say, a single 12-inch diameter, 24-inch deep mailbox post hole, versus when it makes more sense to order a ready-mix truck for a larger job. Combine it with the Concrete Weight Calculator to estimate the total weight of poured concrete for delivery planning.

Who Should Use This Calculator?

  • Fence installers calculating concrete volume across a full run of posts before ordering bagged mix or a ready-mix delivery.
  • Deck builders sizing footings that must meet local frost-depth and load-bearing requirements.
  • DIY homeowners setting a single mailbox post, swing set anchor, or small structure who want to know exactly how many bags to buy.
  • General contractors bidding jobs with multiple round footings, where accurate volume estimates directly affect material cost in the proposal.
  • Landscapers installing posts for pergolas, arbors, or fencing who also use the Concrete Column Calculator for above-grade columns.

What Insights Does the Hole Volume Calculator Give You?

The primary output, Total Volume (cubic yards), is the figure you'll use when ordering ready-mix concrete by the truckload, since suppliers price and deliver by the cubic yard. If your total comes out well under 1 cubic yard, it's usually more economical to use bagged concrete mix instead of ordering a minimum-load delivery.

Total Volume (cu ft) breaks the same result down into cubic feet, which is the more practical unit for converting into bag counts. Since a standard 80 lb bag yields about 0.6 cubic feet of mixed concrete, dividing this figure by 0.6 gives you an approximate bag count for smaller jobs like a handful of fence posts.

How to use this Hole Volume calculator

  1. Measure and enter the Diameter of your hole in inches, this is the width of the auger or excavation, not the post itself.
  2. Enter the Depth of the hole in inches, based on your local frost line and post height requirements.
  3. Set the Number of Holes if you're calculating for a full fence line or multiple footings at once.
  4. Review the Total Volume result in cubic yards to decide whether a ready-mix delivery or bagged concrete is more practical.
  5. Check the Total Volume (cu ft) figure if you're converting to a bag count for a smaller DIY project.
  6. Add 5–10% extra to your final order to account for irregular excavation and spillage during the pour.
Show formula & methodology ↓Show less ↑

Formula & Methodology

The calculator treats each hole as a right cylinder and applies the standard volume formula:

Volume per hole (cu ft) = π × (Diameter ÷ 24)² × (Depth ÷ 12)

Diameter and depth are entered in inches, so dividing diameter by 24 converts it to a radius in feet, and dividing depth by 12 converts it to feet.

Total volume (cu ft) = Volume per hole × Number of holes

Total volume (cu yd) = Total volume (cu ft) ÷ 27

Worked example: For a single hole with a 12-inch diameter and 24-inch depth: radius = 12 ÷ 24 = 0.5 ft, depth = 24 ÷ 12 = 2 ft. Volume = π × 0.5² × 2 ≈ 1.57 cu ft. For 6 such holes, total volume = 1.57 × 6 ≈ 9.42 cu ft, or about 0.35 cubic yards.

Frequently Asked Questions

What is a hole volume calculator used for?
A hole volume calculator estimates the amount of material, usually concrete, needed to fill a cylindrical hole, such as a fence post hole, deck footing, or column footing. It converts the diameter and depth of the hole into a total volume in cubic yards, the standard unit concrete is priced and delivered in.
How does the Hole Volume Calculator work?
The calculator treats each hole as a cylinder and applies the cylinder volume formula using half the diameter as the radius and the depth as the height. It then multiplies the per-hole volume by the number of holes you're digging and converts the total from cubic feet to cubic yards.
What is the formula for cylindrical hole volume?
Volume = π × radius² × depth, where radius is diameter ÷ 2. In this calculator, diameter and depth are entered in inches, so the formula converts both to feet first: volume (cu ft) = π × (diameter ÷ 24)² × (depth ÷ 12).
What is the difference between cubic feet and cubic yards?
A cubic yard equals 27 cubic feet (3 ft × 3 ft × 3 ft), and concrete is typically ordered and priced by the cubic yard, especially for ready-mix deliveries. This calculator shows both figures so you can cross-check smaller quantities in cubic feet against bagged concrete coverage, or larger quantities in cubic yards for truck orders.
How deep should a fence post hole be?
A common rule of thumb is to dig the hole to roughly one-third to one-half of the post's above-ground height, with a minimum depth of 24 inches for most residential fence posts. Local frost line depth and soil conditions can require deeper holes, so check your local building code before finalizing post depth.
How do I use the Hole Volume Calculator?
Enter the hole's Diameter and Depth in inches, then set the Number of Holes if you're calculating for multiple posts or footings at once. The calculator instantly shows the total volume in cubic yards along with the raw cubic feet figure.
Can I use this calculator for deck footings and columns, not just fence posts?
Yes, the cylinder volume formula applies to any round hole regardless of its purpose, including deck footings, mailbox posts, and cylindrical column footings. Just make sure to enter the actual excavated diameter, which is often slightly larger than the auger or post size to allow room for concrete.
Should I subtract the volume of the post itself from the total?
For a small wooden or metal post surrounded by concrete, the post volume is usually negligible and most contractors don't subtract it from the concrete order. For large-diameter posts relative to the hole, you can manually reduce your order slightly, but rounding up is generally safer to avoid a shortfall.
How many bags of concrete equal one cubic yard?
A standard 80 lb bag of concrete mix yields about 0.6 cubic feet, meaning roughly 45 bags are needed to make one cubic yard (27 cubic feet). For smaller jobs, converting your calculator's cubic feet output into bag count is often more practical than ordering a full truck.
Why does hole diameter have such a large effect on volume?
Volume scales with the square of the radius, so doubling the diameter of a hole quadruples its volume, not just doubles it. This is why even a small increase in auger size can significantly increase the amount of concrete needed.
Do I need extra concrete for multiple holes on the same job?
Yes, this calculator multiplies the per-hole volume by your entered quantity, but it's still wise to add 5–10% extra to account for irregular excavation, spillage, and soil variation between holes. Ordering slightly more than the calculated minimum avoids a second trip or delivery for a small shortfall.
Also known as
post hole volume calculatorfooting hole calculatorcylindrical hole volume calculatorconcrete hole calculatorauger hole volume calculator