How many bags of concrete do I need for a 10x10 slab?

For a 10 ft by 10 ft patio slab poured at a standard 4-inch thickness, you will need approximately 1.23 cubic yards of concrete (33.3 cubic feet). Accounting for a recommended 10% waste buffer, you will need about 62 bags of 80-lb concrete, or 82 bags of 60-lb concrete. For a pour this size, ordering a ready-mix truck is often much easier.

What is the standard formula for calculating concrete cubic yards?

The standard formula for rectangular slabs and footings is: Length (feet) × Width (feet) × Thickness (fraction of a foot, i.e., inches ÷ 12) = Cubic Feet. Then divide Cubic Feet by 27 to obtain Cubic Yards. Always add 5% to 10% extra for subgrade unevenness and spillage.

How many 80lb, 60lb, or 50lb bags make 1 cubic yard?

One cubic yard of concrete equals 27 cubic feet. It takes exactly 45 bags of 80-lb concrete (0.60 cu ft/bag), 60 bags of 60-lb concrete (0.45 cu ft/bag), 72 bags of 50-lb concrete (0.375 cu ft/bag), or 90 bags of 40-lb concrete (0.30 cu ft/bag) to equal 1 cubic yard.

When should I order a ready-mix truck instead of mixing bags?

As a general rule of thumb: for projects requiring less than 1 cubic yard (under 45 80-lb bags), mixing bagged concrete on-site in a wheelbarrow or small portable mixer is practical and avoids truck short-load fees. For projects over 1 cubic yard (such as driveways, large patios, foundation footings, and garage floors), ready-mix truck delivery ensures uniform PSI strength and eliminates exhausting manual batching.

What is the ideal concrete mix ratio for DIY on-site mixing?

The standard universal ratio for general-purpose structural concrete (approx 3,000 to 3,500 PSI) is the 1:2:3 mix ratio: 1 part Portland Cement, 2 parts clean sharp Sand, and 3 parts Gravel/Aggregate by volume, with approximately 0.5 parts clean water.

Calculators

Concrete Calculator

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100% Free • Multi-Shape • Bags & Ready-Mix Truck Estimator

Concrete Yardage & Bag Calculator

Calculate exact cubic yards, cubic meters, and bag counts for slabs, footings, round columns, post holes, and stairs with waste margin.

Length (feet)

Width (feet)

Thickness (inches)

Quantity

Waste & Spillage Buffer (%)10% (10% recommended for uneven ground)

Concrete Volume & Material Estimates

1.63 cu yds

≈ 1.25 m³ (44.0 cu ft)

Exact Geometric Volume

1.48 cu yds

Waste Buffer Added

+10%

Includes $80 short-load fee (orders under 4 yd).

Pre-Mixed Bags Required

80-lb Bags (0.60 cu ft)

74 bags

60-lb Bags (0.45 cu ft)

98 bags

25-kg Bags (0.0125 m³)

100 bags

40-kg Bags (0.0200 m³)

63 bags

3D Geometric Model

1.63 cu yds

12ft × 10ft × 4in (1 slab)

Truck vs Bags Recommendation

Your project requires 1.63 cu yds (74 80-lb bags). For pours over 1 cu yd, a Ready-Mix concrete truck saves hours of physical labor, prevents cold joints, and guarantees uniform strength.

Note: Truck orders under 4 cu yds may incur a short-load delivery fee. Truck estimate includes short-load fee.

DIY On-Site Mix Recipe (1 : 2 : 3 Ratio)

Portland Cement: 961 lbs

Clean Sand: 1922 lbs

Gravel / Stone Aggregate: 2884 lbs

Clean Water: 58 gal

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Quick Takeaway

Bottom Line: To calculate concrete volume for any slab or footing, multiply Length (ft) × Width (ft) × Thickness (in ÷ 12) to get Cubic Feet, then divide by 27 to obtain Cubic Yards. Always add 10% extra for subgrade imperfections and spillage.

How to Calculate Concrete Volume: The Definitive Guide

One cubic yard equals 27 cubic feet. A standard 10' × 10' patio poured 4 inches thick requires 1.23 cubic yards or 62 bags of 80-lb concrete.

Recommended Concrete Thickness by Project

Sidewalks, patios, and sheds: 4 inches (10 cm). Residential driveways and garage slabs: 5 to 6 inches (13–15 cm) with rebar reinforcement. Heavy equipment slabs: 6 to 8 inches (15–20 cm).

DIY Structural Concrete Ratio (1:2:3)

For general residential structural concrete (3,000–3,500 PSI), mix 1 part Portland cement, 2 parts sand, and 3 parts coarse gravel by volume with approximately 0.5 parts water.

Concrete Bag Yield & Coverage Chart (per Cubic Yard / m³)

Bag Size	Volume Yield	Bags / Cubic Yard	Bags / Cubic Meter (m³)
80 lb (36.3 kg)	0.60 cu ft (0.017 m³)	45 bags	59 bags
60 lb (27.2 kg)	0.45 cu ft (0.013 m³)	60 bags	78 bags
50 lb (22.7 kg)	0.375 cu ft (0.011 m³)	72 bags	94 bags
25 kg (55.1 lb)	0.44 cu ft (0.0125 m³)	61 bags	80 bags
40 kg (88.2 lb)	0.71 cu ft (0.0200 m³)	38 bags	50 bags

Frequently Asked Questions

For a 10' × 10' slab poured 4 inches deep, you need approximately 1.23 cubic yards (including a 10% waste buffer). This requires about 62 bags of 80-lb concrete or 82 bags of 60-lb concrete.