Bag vs Yard Concrete Calculator: Converting and Deciding

Every concrete project eventually forces the same decision: do I buy bags and mix them by hand, or do I order a truck of ready-mix measured in cubic yards? The two are measuring the same thing — volume — but they price completely differently, and the crossover point is the most useful number a DIYer can know. This guide gives you the conversion chart, the breakeven math, and the rule of thumb that settles the debate.

The Bag-to-Yard Conversion

Everything starts with one fixed fact: one cubic yard is 27 cubic feet. Bagged concrete is sold by weight, and each bag size yields a specific finished volume:

• 40 lb bag: about 0.30 cubic feet — 90 bags per yard
• 60 lb bag: about 0.45 cubic feet — 60 bags per yard
• 80 lb bag: about 0.60 cubic feet — 45 bags per yard

So to convert any project to bags, find its volume in cubic feet, then divide by the bag's yield. To convert to yards, divide by 27. A project that is 2 cubic feet needs about 3.3 bags of 80 lb mix; a project that is 30 cubic feet needs 30 / 27 = 1.11 yards, or 50 bags of 80 lb. The calculator at the top of this page does this conversion in both directions for you, including the waste factor.

The Breakeven Math

Now the money. Price per cubic yard:

• Bags: 45 bags of 80 lb at $6 to $8 each = $270 to $360 per yard of material, plus hours of labor mixing it.
• Ready-mix: $130 to $190 per yard delivered, but trucks charge a short-load fee of $50 to $150 for orders under about 3 to 8 yards.

Here is a worked breakeven for a project needing exactly 1 cubic yard. Ready-mix: 1 yard at $160 plus a $100 short-load fee = $260 delivered. Bags: 45 bags at $7 = $315 in material, plus a full day of mixing. Even at one yard, the truck wins once you value your labor. Now a smaller project needing 0.3 yards (about 8.1 cubic feet, or 14 bags of 80 lb): ready-mix at $160 + $100 short-load fee for a third of a yard = $260, versus 14 bags at $7 = $98 in material. Here bags win decisively. The crossover where the truck becomes cheaper is right around half a cubic yard — roughly 13.5 cubic feet, a 4x4 slab at 4 inches, or a few small footings.

Beyond Price: Speed, Labor, and Quality

The breakeven is only half the decision. Ready-mix arrives already mixed to a consistent spec, which means uniform strength across the whole pour — a huge advantage on anything larger than a tiny pad. A truck pours a full project in minutes instead of hours of wheelbarrow work. The flip side is the time pressure: you have to be fully ready when the truck arrives, because a yard of concrete starts setting within about 90 minutes and there is no pausing it. Bags, by contrast, let you work at your own pace and make exactly as much as you need per batch, but every batch you mix by hand risks inconsistency, and the labor is punishing on anything over a few bags. For most projects above half a yard, the truck wins on every axis.

Short-Load Fee Rule

Many homeowners order bags for a 0.5-yard job out of fear of the truck, but that is often a mistake. Check your local plant's minimum — if it is 1 yard and your project needs 0.6 yards, the short-load fee is small relative to the labor you save, and a single truck is the cleaner choice. If your project needs less than about half a yard, or if a truck physically cannot reach the forms, bags are the right call. And remember: whatever you choose, add the 10% waste factor. Running out means either a second short-load trip or a cold joint, both of which cost more than the 10% buffer. Enter your project's dimensions in the calculator to get both the bag count and the truck yardage at once, then apply the half-yard rule to decide.