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ConcreteVerified Formulas

Concrete Calculator

Calculate concrete volume in cubic yards and convert to 50, 60, or 80-lb premix bags.

Concrete Calculator Interactive Tool

Interactive Calculator

Enter your project dimensions below. Results update instantly.

4 inches is standard for residential slabs & patios
typical value, change to match your product10% accounts for subgrade variation & form deflection

Bag Yield Specifications

typical value, change to match your productStandard 80-lb premix yields 0.60 cu ft
typical value, change to match your productStandard 60-lb premix yields 0.45 cu ft
typical value, change to match your productStandard 40-lb premix yields 0.30 cu ft

Results

Base Volume

2.47 cu yd

66.7 cu ft (exact dimensions)
Concrete to Order

2.72 cu yd

Includes +10% formwork buffer (73.3 cu ft)
80-lb Bags (Premix)

123

At 0.6 cu ft/bag
60-lb Bags (Premix)

163

At 0.45 cu ft/bag
40-lb Bags (Premix)

245 bags

Smaller lightweight bags (at 0.3 cu ft/bag)
Ready-Mix Truck RecommendedYour project exceeds 1.5 cubic yards. Ordering a transit mixer truck is significantly faster and more structurally uniform than hand-mixing 80+ bags.

Concrete Volume & Bag Formulas

Volume (cu yd) = (cu ft ÷ 27) × (1 + Waste % ÷ 100) | 80-lb Bags = ⌈Adjusted cu ft ÷ 0.60⌉ | 60-lb Bags = ⌈Adjusted cu ft ÷ 0.45⌉

Formula Variables:

  • 80-lb Bag Yield:Yields approximately 0.60 cubic feet of mixed concrete (45 bags = 1 cu yd).
  • 60-lb Bag Yield:Yields approximately 0.45 cubic feet of mixed concrete (60 bags = 1 cu yd).
  • 50-lb Bag Yield:Yields approximately 0.375 cubic feet of mixed concrete (72 bags = 1 cu yd).

Always order 10% extra concrete to account for uneven subgrade, spillage, and formwork deflection.

Step-by-Step Worked Example

Example: 10 × 12 ft patio slab at 4 inches thick with 10% safety buffer

Pouring an outdoor grill patio measuring 10 ft by 12 ft with standard 4-inch forms.

Area:10 ft × 12 ft (120 sq ft)
Thickness:4 inches
Waste:10%
  1. Calculate cubic feet: 120 sq ft × (4 ÷ 12) = 40.0 cu ft.
  2. Add 10% buffer: 40.0 × 1.10 = 44.0 cu ft.
  3. Convert to cubic yards: 44.0 ÷ 27 = 1.63 cu yd.
  4. 80-lb bags: 44.0 ÷ 0.60 = 73.3 → 74 bags.
  5. 60-lb bags: 44.0 ÷ 0.45 = 97.8 → 98 bags.
Requires 1.63 cubic yards. If mixing bags by hand, purchase 74 eighty-pound bags (or 98 sixty-pound bags).

Input Explanations & Measurement Guidelines

Dimensions / Volume

Typical: 10 × 12 ft × 4 in

Length, width, and depth of the planned concrete pour.

Waste Allowance

Typical: 10%

Industry-standard buffer for form spreading and uneven sub-base.

Assumptions & Limitations

  • Assumes standard 3,000 to 4,000 PSI bagged premix or transit-mix concrete.
  • For projects over 1.5–2 cubic yards, ready-mix truck delivery is strongly recommended over manual hand-mixing.

Safety & Professional Notes

  • Wet concrete is strongly alkaline (pH 12–13) and causes severe chemical skin burns. Always wear rubber boots, waterproof gloves, and eye protection.
Recommended Guide · 8 min read

How to Calculate Concrete Volume: Slabs, Footings & Bag Counts

Concrete cannot be returned once ordered or mixed. Underestimating volume leads to disastrous cold joints, while overestimating wastes hundreds of dollars. Learn how to calculate precise concrete volume.

Read Guide

Frequently Asked Questions

When should I call a concrete truck instead of mixing bags?

The practical threshold is 1.5 to 2 cubic yards. Mixing 80+ heavy bags by hand or small rental mixer takes hours and risks cold joints where early batches cure before later batches are poured.

How much water do I add to an 80-lb bag of concrete?

Most standard 80-lb bags require roughly 3 quarts (2.8 liters) of clean water. Adding too much water significantly weakens cured compressive strength.

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