6 holes, 12 in diameter x 30 in deep
- Cubic yards
- 0.4266360394
- Concrete per hole
- 1.745329252 ft3
- 60 lb bags
- 26
Hole depth should follow frost, soil, fence, deck, or code requirements. This only estimates concrete volume around the post.
Post Hole Concrete Calculator
Use this free post hole concrete calculator to estimate concrete volume and bag counts from hole diameter, hole depth, post diameter, quantity, and waste.
Research-backed assumptions Formula steps Examples included Private in-browser use
Formula steps
- Find round hole volume from diameter and depth.
- Subtract the round post volume occupying the hole.
- Multiply by hole count, add waste, and round bag counts up.
How to use the post hole concrete calculator
- Enter hole diameter, hole depth, post diameter, hole count, and waste percent.
- Press Estimate post holes to see concrete volume and bag counts.
- The tool subtracts the post volume from the hole volume.
- Frost depth, soil, gates, decks, gravel bases, and local code can change the real hole design.
Common uses
Estimate concrete bags for fence posts.
Plan concrete for deck support holes.
Subtract post volume from round hole volume.
Compare hole sizes before buying concrete.
Examples
About 20 eighty-pound bags
Post concrete estimate
Small bag estimate
Frequently asked questions
Plain-language answers about when to use the tool, what it does with your inputs, what to double-check, and how privacy works.
When should I use the Post Hole Concrete Calculator?
Use it when your task matches one of these common needs: Estimate concrete bags for fence posts. Plan concrete for deck support holes. It works best when you already know the values, dates, units, or settings the page asks for.
What is the Post Hole Concrete Calculator doing with my inputs?
In plain language: The calculator finds the round hole volume, subtracts the round post volume inside the hole, multiplies by the number of holes, adds waste, and rounds bag counts up. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
What do the main Post Hole Concrete Calculator inputs mean?
Hole diameter: the width across the round hole in inches. Hole depth: the filled depth in inches. Post diameter: the width of the post that takes up space inside the hole. Quantity: how many matching holes to estimate.
How should I read the Post Hole Concrete Calculator answer?
Read the headline estimate first, then check the material, waste, coverage, and unit lines. For project tools, the supporting lines are often the difference between a rough idea and a list you can actually shop from.
What should I double-check before trusting the answer?
Post depth, hole width, gravel base, frost depth, uplift, gate loads, deck loads, and local code can change what you actually need. Also check that you used the right unit, date, scale, or mode because small input changes can change the result.
Why does the calculator subtract the post volume?
The post occupies part of the hole, so concrete only fills the space around it. Subtracting the post keeps the estimate closer than treating the whole hole as concrete.
What if my post is square?
Use the closest equivalent diameter for a rough estimate or calculate the square post area separately. For big jobs, a contractor takeoff is safer.
Does the site save what I enter?
No. The calculator runs in your browser tab. Your recent answers stay only on the page while you use it, and they are not sent to a server.
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