How many 80 lb bags equal a cubic yard?

A cubic yard is 27 ft³. At 0.60 ft³ per 80 lb bag, you need 45 × 80 lb bags to pour one cubic yard.

Should I use 40, 60, or 80 lb bags?

80 lb bags are the cheapest per cubic foot. Use 60 lb if 80 lb is too heavy to lift comfortably. 40 lb is best for small post-hole patches.

When should I order ready-mix instead of bags?

Once you need more than ~30 × 80 lb bags (about 0.7 yd³), ready-mix from a truck is usually cheaper and faster. Most ready-mix plants have a 1-yard minimum and short-load fees.

How much waste should I add?

5% for ready-mix in a flat slab. 10% for bagged concrete or any pour with footings, steps, or odd shapes. Concrete cannot be "topped up" once placed, so always round up.

Does this calculator size rebar?

No. It returns volume only. Rebar size, spacing, and depth depend on load and span; consult an engineer or local code for structural work.

Is this calculator free?

Yes — completely free, runs in your browser, no signup or upload.

Concrete Calculator

Concrete volume in yd³/m³ and 40/60/80 lb bag count for slabs, footings, and columns.

Written by Golam Rabbani, Founder & Lead Engineer

This interactive tool requires JavaScript. Read the formula and worked example below; you can compute the result by hand.

How to use this concrete calculator

Pick imperial (ft / in) or metric (m / cm) using the unit toggle.
Choose the shape: Slab, Footing, Column (round), or Cylinder.
Enter length, width, and depth — or diameter and height for columns and cylinders.
Set the waste / overage percentage (5–10% recommended).
Press Calculate to see the volume in cubic yards, cubic metres, and bag counts.

About this concrete calculator

The concrete calculator computes how much concrete you need, in cubic yards or cubic metres, plus the number of pre-mixed bags to buy in three common sizes (40, 60, and 80 lb). Slabs and footings use length × width × depth. Round columns and cylinders use π × radius² × height. The result is multiplied by 1 plus your waste percentage, then divided by the published yield of each bag size: 0.30 ft³ per 40 lb bag, 0.45 ft³ per 60 lb bag, and 0.60 ft³ per 80 lb bag.

Worked example: a 10 ft × 10 ft slab poured 4 inches thick has 33.33 ft³ of concrete. Adding a 5% waste factor brings that to 35.0 ft³, which is 1.30 yd³ or 0.99 m³. To pour the same job with bagged premix, you need 35.0 ÷ 0.60 = 58.4, rounded up to 59 × 80 lb bags. Most pros order ready-mix from a truck for any slab over a yard; bags are practical for footings, post holes, and small repairs.

Order at least 5% extra for any pour, and 10% for irregular footings or hand-mixed jobs — concrete is impossible to add to a partial pour once it begins to set. For structural slabs and footings, consult an engineer; the calculator gives volume only and does not size reinforcement.

FAQ

How many 80 lb bags equal a cubic yard?: A cubic yard is 27 ft³. At 0.60 ft³ per 80 lb bag, you need 45 × 80 lb bags to pour one cubic yard.
Should I use 40, 60, or 80 lb bags?: 80 lb bags are the cheapest per cubic foot. Use 60 lb if 80 lb is too heavy to lift comfortably. 40 lb is best for small post-hole patches.
When should I order ready-mix instead of bags?: Once you need more than ~30 × 80 lb bags (about 0.7 yd³), ready-mix from a truck is usually cheaper and faster. Most ready-mix plants have a 1-yard minimum and short-load fees.
How much waste should I add?: 5% for ready-mix in a flat slab. 10% for bagged concrete or any pour with footings, steps, or odd shapes. Concrete cannot be "topped up" once placed, so always round up.
Does this calculator size rebar?: No. It returns volume only. Rebar size, spacing, and depth depend on load and span; consult an engineer or local code for structural work.
Is this calculator free?: Yes — completely free, runs in your browser, no signup or upload.