Post Hole Calculator

Calculate concrete and gravel needed for setting fence or deck posts in the ground.

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How to Use This Calculator

<h4>How to Use</h4><ol><li>Enter the number of post holes to dig.</li><li>Enter hole diameter and depth.</li><li>Enter the post size (width) to subtract from the volume.</li><li>Optionally set the gravel base depth.</li></ol><h4>Tips</h4><ul><li>A general rule: hole diameter should be 3× the post width.</li><li>Set posts at least 1/3 of their total length into the ground.</li><li>Add 75 mm (3 in) of gravel at the base for drainage.</li></ul>

Common Questions

How deep should a fence post hole be?

A common rule is to bury 1/3 of the total post length. For a 6 ft (1.8 m) fence with 8 ft (2.4 m) posts, that is about 24–30 inches (600–750 mm) deep.

How many bags of concrete per post?

For a standard 4×4 post in a 10-inch diameter, 24-inch deep hole, you will need about 1–2 bags of 60 lb concrete mix.

Should I use gravel at the bottom?

Yes, 3–4 inches (75–100 mm) of gravel improves drainage and prevents the post base from sitting in water.

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