Estimate concrete around round posts
Post Hole Concrete Calculator
Use this post hole concrete calculator to estimate concrete for round fence-post holes. Enter the hole diameter and concrete depth, then optionally subtract a round post occupying that full depth; bag counts use your selected product yield.
Round hole estimate
Measurement system: Imperial. Planning estimate based on the dimensions and allowance shown below.
Build your estimate
Choose a shape, enter measured dimensions, then review every step.
The optional round post is subtracted through the full concrete depth.
Bag yields and product settings
Yield differs by product. These common examples are editable.
Bag counts are rounded up. The 40, 50, 60, and 80 lb rows show common US products; use the package yield for your product.
Optional: price your materials
Enter local prices. No regional or supplier price is assumed.
Material estimate only. Delivery, taxes, labor, and supplier minimums are not included.
Calculation and assumptions
Subtract the round post from the round hole
Worked example: 12 in hole, 3 in round post, 36 in concrete depth
- Convert the dimensions to feet: hole diameter 1 ft, post diameter 0.25 ft, and depth 3 ft.
- Net volume per hole = π × (0.5² − 0.125²) × 3 = 2.21 ft³, or about 0.082 yd³.
- With a chosen 10% allowance, one hole needs about 2.43 ft³ before whole-bag rounding.
Post displacement has specific limits
- The optional displacement is circular and assumes the post occupies the entire entered concrete depth.
- This does not model square posts, tapered or irregular holes, sloped tops, or posts that extend only partway through the concrete.
- The post diameter must be smaller than the hole diameter. For a square post, measure the actual concrete region or calculate the geometry separately.
All example quantities are geometry and arithmetic illustrations. Confirm measurements, product yields, ordering rules, and project requirements with your plans and supplier.