Post-hole concrete Calculator: measuring notes and method
Measure hole and post separately
Measure the concrete-filled depth, which may be less than the excavated depth. Use Quantity only for holes with matching hole diameter, round post diameter and filled depth. Save gate posts and other differently sized holes as separate project items.
If the post stops above the hole bottom
Calculate the annular part around the post here, then add a separate solid cylinder for concrete below it. For a square post, subtract side × side × embedded depth from the round-hole volume separately.
Formula
Concrete = π × (hole diameter² − post diameter²) ÷ 4 × depth × quantity. Apply waste.
Product reference: QUIKRETE product yields
Worked examples in metric and imperial units
Illustrative values match Reset example and stay fixed when you edit the calculator. Both columns describe the same calculation; converted inputs are rounded.
Metric worked example
- Hole diameter
- 300 mm
- Round post diameter
- 100 mm
- Filled depth
- 0.6 m
- Quantity
- 8
- Waste allowance
- 10 %
Concrete required: 0.3318 m³
Imperial worked example
- Hole diameter
- 11.811 in
- Round post diameter
- 3.937 in
- Filled depth
- 1.9685 ft
- Quantity
- 8
- Waste allowance
- 10 %
Concrete required: 0.4339 yd³
Follow the calculation
Lengths in this working are in metres.
- Hole area minus round post area = π × (0.3² − 0.1²) ÷ 4 = 0.062832 m².
- Multiply that area by 0.6 m filled depth, 8 holes and the 1.1 allowance multiplier.
Unit conversions
1 m³ = 1,000 L ≈ 1.30795 yd³. One cubic yard is 27 ft³.
Reviewed 19 October 2026. How calculations are checked · Report a correction