How many 80 lb bags of concrete are in a cubic yard?

About 45. A cubic yard is 27 cubic feet and an 80 lb bag yields roughly 0.60 cubic feet, so 27 ÷ 0.60 = 45 bags. For 60 lb bags it is 60 bags per cubic yard.

How thick should a concrete patio be?

Four inches over a compacted base is standard for a patio, walkway or shed pad carrying foot traffic. Go to six inches where vehicles will park, and check local requirements for anything structural.

Should I order ready-mix or mix bags myself?

Roughly speaking, under half a cubic yard bags are easier, and over a cubic yard ready-mix is both cheaper and far less work. Between those, it depends on how many hands you have and whether the pour needs to be finished in one go.

Concrete Calculator

Work out cubic yards of concrete and how many 60 lb or 80 lb bags a slab, footing or pad needs.

Draft — figures checked, awaiting an editorial read. Not indexed.

Concrete needed— yd³Ready-mix is ordered in cubic yards.

Volume: — ft³
60 lb bagsEach yields about 0.45 ft³.: — bags
80 lb bagsEach yields about 0.60 ft³.: — bags
Volume: — m³

Formula: Volume (ft³) = length × width × (thickness ÷ 12), then ÷ 27 for cubic yards. Bags = volume ÷ bag yield.

What this calculates

This works out how much concrete a rectangular pour needs, in the units you actually buy it in. Enter the footprint and the slab thickness and you get cubic yards for a ready-mix order, plus a bag count if you are mixing on site. The distinction matters more than it looks: below about half a cubic yard, bags are cheaper and simpler, and above roughly one cubic yard, mixing by hand stops being realistic — a cubic yard is around forty-five 60 lb bags, which is close to a ton of material through a wheelbarrow. Use it for slabs, patios, walkways, shed pads, and footings of constant depth.

How it works

Volume is length times width times thickness, with the thickness converted from inches to feet by dividing by twelve. That gives cubic feet, which divides by twenty-seven to reach cubic yards, since a cubic yard is three feet cubed. The bag counts come from the yield printed on the bag rather than from the bag weight: a 60 lb bag of pre-mixed concrete produces about 0.45 cubic feet of set concrete and an 80 lb bag about 0.60. The waste allowance is applied to the volume before any of the conversions, so it flows through to every figure consistently.

Worked example

A 12 ft by 10 ft patio at 4 inches thick: 12 × 10 × (4 ÷ 12) = 40 cubic feet. Divided by 27 that is 1.48 cubic yards. Add a 5% waste allowance and you are at 42 cubic feet, or 1.56 cubic yards — so you would order 1.75 yards, since ready-mix is normally sold in quarter-yard increments. As bags, 42 ÷ 0.45 is 94 bags of 60 lb, or 70 bags of 80 lb. That is a clear case for ready-mix.

Common mistakes

The big one is entering thickness in inches into a formula expecting feet, which produces a number twelve times too large — this calculator handles the conversion, so enter inches as inches. The second is ordering the exact calculated amount. Subgrade is never perfectly level, and a slab that averages half an inch deeper than planned over 120 square feet swallows an extra five cubic feet. Order slightly long; a short pour that sets before the second batch arrives leaves a cold joint you cannot undo.

Common questions

How many 80 lb bags of concrete are in a cubic yard?: About 45. A cubic yard is 27 cubic feet and an 80 lb bag yields roughly 0.60 cubic feet, so 27 ÷ 0.60 = 45 bags. For 60 lb bags it is 60 bags per cubic yard.
How thick should a concrete patio be?: Four inches over a compacted base is standard for a patio, walkway or shed pad carrying foot traffic. Go to six inches where vehicles will park, and check local requirements for anything structural.
Should I order ready-mix or mix bags myself?: Roughly speaking, under half a cubic yard bags are easier, and over a cubic yard ready-mix is both cheaper and far less work. Between those, it depends on how many hands you have and whether the pour needs to be finished in one go.