How Much Concrete for an 8x8 Pad? Bags vs Ready-Mix

How much concrete for an 8x8 pad is about 0.79 cubic yards at 4 inches thick, or 21.3 cubic feet. That equals roughly 36 bags of 80-pound concrete or 48 bags of 60-pound concrete before waste. At 6 inches it rises to about 1.19 cubic yards, or about 54 bags of 80-pound mix. An 8x8 pad is right at the size where bagged concrete is still practical and a small ready-mix order starts to make sense.

Concrete calculator →

Volume at different thicknesses

Thickness	Cubic feet	Cubic yards	80-lb bags	60-lb bags
3.5 inches	18.7	0.69	32	42
4 inches	21.3	0.79	36	48
5 inches	26.7	0.99	45	60
6 inches	32.0	1.19	54	72

These assume about 0.6 cubic feet per 80-pound bag and 0.45 cubic feet per 60-pound bag. Add about 10 percent for spills, base dips, and form bulge.

The math

Area is 8 × 8 = 64 square feet. Multiply by thickness in feet (4 inches = 0.333 ft) to get 21.3 cubic feet, then divide by 27 to get 0.79 cubic yards. For bags, divide cubic feet by the bag yield. The concrete calculator handles both.

Bags or ready-mix?

Bags make sense when: - You have two or three helpers and a rented mixer. - The pad is far from where a truck can park. - You want to pour on your own schedule.

Ready-mix makes sense when: - You need about a yard or more, as with a 6-inch pad. - You want one continuous pour with a uniform finish. - Your time and back are worth more than the short-load fee.

Many plants charge a short-load fee for small orders. Some areas also have trailer-mix or “U-cart” services that sell a yard or less. See ready-mix vs bagged concrete and the short-load fee page.

Common uses and thickness

Generator or heat pump pad: often 4 inches, though some units ship with or call for a composite pad. Check the installation manual for clearances.
Hot tub pad: 4 inches is the common minimum for an 8x8 spa footprint; follow the spa maker’s guidance, since a filled tub can weigh several thousand pounds.
Grill or smoker pad: 4 inches.
Small shed or trash enclosure: 4 inches, sometimes with thickened edges.

Base and forms

Dig out enough for 4 inches of compacted gravel plus the slab. For an 8x8 pad that is about 0.8 cubic yards of base, a little over a ton of crushed stone. Set 2x4 or 2x6 forms, stake them every 2 to 3 feet, and slope the top about 1/8 inch per foot away from any building so water drains.

Mixing bags without trouble

With 36 to 54 bags, work in batches of two or three bags in a mixer and keep the water consistent from batch to batch. Have one person mixing, one wheeling, and one screeding. If the first batches stiffen before the last arrive, rough up the edge and keep going quickly so the batches bond.

Bottom line

An 8x8 pad needs about 0.79 cubic yards of concrete at 4 inches, which is about 36 bags of 80-pound mix, or about 1.19 yards at 6 inches. Add about 10 percent and decide between bags and a small ready-mix load based on access, help, and local short-load fees.

Questions people ask

How many bags of concrete for an 8x8 slab?

About 36 bags of 80-pound concrete at 4 inches thick, or 48 bags of 60-pound concrete, before waste.

How many yards of concrete for an 8x8 pad?

About 0.79 cubic yards at 4 inches and 1.19 cubic yards at 6 inches.

How thick should an 8x8 hot tub pad be?

Four inches on compacted gravel is a common minimum. Check the spa maker’s requirements.

Is it cheaper to use bags or ready-mix for an 8x8 pad?

Bags can cost less for a 4-inch pad, but a short-load ready-mix order may be worth it for labor and finish quality.

How much gravel do I need under an 8x8 pad?

About 0.8 cubic yards at 4 inches deep, a little over a ton of crushed stone.

As an Amazon Associate, AsphaltTons.com earns from qualifying purchases. Product links below are sponsored.