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The Post Hole Concrete Calculator is a user-friendly tool designed to help users efficiently determine the required number of concrete bags, total cost, and water usage for fence post holes of varying depths and dimensions.
It simplifies the calculation process by allowing users to input their desired post hole depth, dimensions, and the total number of fence posts needed (up to 500).
A common rule of thumb is about 1.5–2 bags of 50‑lb concrete per hole for many standard fence posts (often a 10–12 inch diameter hole at 24–30 inches deep). Gate posts, deeper frost lines, wider holes, and larger posts require more.
The best approach is to calculate it from your hole diameter, depth, and post count—then price it using your local bag cost so you don’t overbuy or run short.
Use this as a fast sanity‑check, then scroll to the calculator for an exact number.
| Common hole setup | Typical 50‑lb bags / hole | Typical 80‑lb bags / hole | Notes |
|---|---|---|---|
| 8" dia × 24" deep | ~1 | ~1/2 | Light fence, mild soils |
| 10" dia × 30" deep | ~1.5–2 | ~1 | Very common residential setup |
| 12" dia × 36" deep | ~3–4 | ~2 | Deeper set / heavier loads |
| Gate posts (typical) | Often +25–50% | Often +25–50% | More load + leverage |
Jump to: calculator • FAQs
The calculator then provides the volume per post hole, bags of premixed concrete per post hole, total bags needed, total gallons of water required, and the overall cost of premixed concrete.
This versatile calculator is an essential resource for anyone planning a fencing project, making it easier to accurately estimate materials and costs.
Concrete volume per hole = π × (radius²) × depth. Convert inches to feet first, then multiply by the number of holes. Finally, divide by your bag yield to estimate how many 50‑lb or 80‑lb bags you need.
If you don’t want to do conversions, use the calculator below—it performs the math and estimates cost and water.
Every tree planted is a metric waiting to be measured by a tree calculator.
It depends on hole diameter, depth, and post size. A common rule is a hole ~3× the post width and 1/3–1/2 of the post length in the ground. For a 4×4 post in a 10–12 in (25–30 cm) hole, expect roughly 1.5–2 bags of 50–60 lb fast-setting mix; larger posts or deeper holes require more.
Bury 1/3–1/2 of the post length, and at least to/below your local frost line to reduce heave. Typical residential runs: 2–3 ft (0.6–0.9 m) for 6–8 ft fences, deeper for gate posts or high-wind areas.
Fast-setting mixes set in ~20–40 minutes and are great for small projects and quick bracing removal. Standard mixes have longer working time, useful in heat, for large holes, or when aligning multiple posts. Both reach comparable strengths when cured per instructions.
Yes, many manufacturers allow dry-setting—pour dry mix around the post and water per bag directions. It’s convenient for small holes and good drainage soils. For poor drainage or structural posts (e.g., gates), premixing often yields more reliable hydration.
Light handling is often possible after a few hours with fast-set concrete, but wait 24–48 hours before loading posts; full cure takes up to 28 days. Wind bracing during early cure helps keep posts plumb.
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