Yard & Slab — Jobsite Material Estimate

Precision US Contractor & Building Material Calculations (yardandslab.com)

Date: October 28, 2026

Standards: US Imperial (ASTM / Quikrete / IRC)

100% US Imperial Standard: All formulas calibrated for US Retail SKUs (80lb/60lb Bags, Cubic Yards, US Tons & Gallons)
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Post Hole Concrete Estimator

Calculate bags of fast-setting concrete for fence or deck posts. Subtracts the displaced post volume from cylindrical hole volume.

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🪵 Post Hole & Timber Specifications

Rule of thumb: 3× post diameter
1 post
1 post 20 posts 40 posts
📐 Submerged Timber Displacement Subtracted: A nominal 4x4 post displaces ~0.255 cu ft of concrete. We subtract this submerged volume so you don't over-purchase concrete bags.
Total Concrete Requirement

4 Bags (50lb Fast-Setting)

Per Hole

4 bags

1.381 cu ft net

Hole Volume: 1.636 cu ft Post Displaced: -0.255 cu ft Total Weight: 200 lbs

Drilled Post Hole Cutaway Diagram

10" Dia × 36" Deep
Grade Line 4" Gravel Footing 4x4 Post 10" Dia 36" Depth

🛒 Post Setting Shopping List

50 lb Quikrete Fast-Setting Concrete No mixing required — pour dry into water
4 bags Check Home Depot ›
60 lb Standard Concrete (Alternative) Requires pre-mixing; higher 4,000 PSI strength
4 bags (4 per hole)
Pea Gravel Bottom Drainage Base Prevents post bottom rot
0.18 cu ft ~1 bags (0.5 cu ft)
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📐 Engineering Principles & Formulas

All calculations adhere strictly to US Imperial standards and standard retail SKU yields (Quikrete, Home Depot, Lowe's, ASTM standards):

• Cylindrical Hole Volume = π × [Diameter (in) ÷ 24]² × [Depth (in) ÷ 12] • Submerged Post Displacement = (Actual Width ÷ 12)² × [Depth ÷ 12] (4x4 = 3.5", 6x6 = 5.5") • Net Concrete = Hole Volume - Post Volume • 50-lb Fast-Setting Bags = Net cu ft ÷ 0.375 cu ft/bag

Pre-Solved Dimension Calculators

16 Pre-Calculated Sizes

Jump directly to your exact dimensions with pre-solved material quantities and instant answers:

How Many Bags of Concrete for a 4x4 Post in a 8" Hole × 24" Deep? › How Many Bags of Concrete for a 4x4 Post in a 8" Hole × 30" Deep? › How Many Bags of Concrete for a 4x4 Post in a 8" Hole × 36" Deep? › How Many Bags of Concrete for a 4x4 Post in a 10" Hole × 30" Deep? › How Many Bags of Concrete for a 4x4 Post in a 10" Hole × 36" Deep? › How Many Bags of Concrete for a 4x4 Post in a 10" Hole × 42" Deep? › How Many Bags of Concrete for a 4x4 Post in a 10" Hole × 48" Deep? › How Many Bags of Concrete for a 6x6 Post in a 10" Hole × 36" Deep? › How Many Bags of Concrete for a 6x6 Post in a 12" Hole × 36" Deep? › How Many Bags of Concrete for a 6x6 Post in a 12" Hole × 42" Deep? › How Many Bags of Concrete for a 6x6 Post in a 12" Hole × 48" Deep? › How Many Bags of Concrete for a 6x6 Post in a 14" Hole × 48" Deep? › How Many Bags of Concrete for a 2-3/8 round Post in a 8" Hole × 30" Deep? › How Many Bags of Concrete for a 2-3/8 round Post in a 8" Hole × 36" Deep? › How Many Bags of Concrete for a 2-3/8 round Post in a 10" Hole × 36" Deep? › How Many Bags of Concrete for a 2-3/8 round Post in a 10" Hole × 42" Deep? ›

🔗 Free Contractor Website Embed Widget

Contractors, builders, and suppliers can embed this interactive Post Hole Concrete Estimator on their website for free.

<iframe src="https://yardandslab.com/embed/post-hole-concrete-calculator" width="100%" height="650" frameborder="0" style="border:1px solid #e2e8f0;border-radius:12px;"></iframe>

❓ Frequently Asked Questions: Post Hole Concrete Estimator

Yes. Every calculation outputs standard US construction packaging and measurements: cubic yards, 40lb/60lb/80lb Quikrete bags, US short tons (2,000 lbs), fluid ounces, gallons, and linear feet matching Home Depot and Lowe's retail inventory.
Yes. Calculators default to a contractor-standard 10% waste factor to accommodate form flex, uneven subgrades, and spillage. You can adjust this to 5% or 15% using the interactive input controls.
Generic calculators rely on basic geometric boxes without considering physical building realities: corrugated pipe displacement in French drains, actual nominal post sizes (3.5" for 4x4, not 4.0"), 15% compaction factors for crushed aggregate, and IECC US Climate Zones.
Yes! Click the "Print / PDF" button on any calculator to generate a clean, branded one-page materials shopping list formatted for mobile or paper printout at the lumberyard.