How many 80-lb bags equal a yard of concrete?

You need about 45 80-lb bags to make one cubic yard of mixed concrete. Each 80-lb bag yields ~0.6 ft³.

What is the standard concrete slab thickness?

Walkways and patios use 4 inches. Driveways for cars use 4–5 inches; for trucks 6–8 inches. Garage slabs typically use 4 inches with reinforcement.

How long does concrete take to cure?

Concrete reaches ~70% strength in 7 days and 100% (28-day strength) in roughly 28 days. Heavy traffic should wait at least 7 days.

Can I pour concrete in cold weather?

Per ACI 306, do not pour below 40°F without admixtures and blankets. Use our weather-window tool to find the best days.

What waste percentage should I use?

5–10% is standard. Use 10% for hand-mixed bag work, 5% for ready-mix truck delivery.

How much concrete do I need?

Quick answer: enter your dimensions in the Concrete Calculator below to see yards, bags, and an optional cost estimate. Most home projects can be answered in under a minute.

Concrete Calculator

Calculate cubic yards, cubic meters, and the number of 40, 60, and 80-lb concrete bags for slabs, footings, columns, and stairs. Optional price input gives a full project cost.

Inputs

Project type

Length(ft)

Width(ft)

Thickness(in)

Diameter (column only)(in)

Height (column only)(ft)

Waste %

Price per yd³ (optional)($)

Result

Volume

1.36 yd³

Metric

1.04 m³

80-lb bags

60-lb bags: 82
40-lb bags: 123
Cubic feet: 36.7 ft³
Waste included: 10%

Waste default: 10% — ACI 301 recommends a 5–10% overage to account for sub-grade variation and spillage.

Diagram

Estimates only. Verify with a licensed contractor or supplier before purchasing. Rough Estimator! is not responsible for shortages, overages, or material variances. See our methodology for formulas and sources.

Formula

Volume (yd³) = L × W × D ÷ 27   ·   Bags (80 lb) = Volume (ft³) ÷ 0.6

References

Pour-window forecast

Free 7-day forecast from Open-Meteo. Green = safe to concrete. We never share your location.

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Frequently asked questions

A 10×10 patio at 4 inches thick needs roughly 1.23 cubic yards (about 51 80-lb bags) including a 10% waste factor.

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Cosyslabs. (2026). Concrete Calculator. Rough Estimator!. https://roughestimator.com/concrete-calculator

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