Answer · Concrete

How many 80 lb bags of concrete for a 10×10 slab?

Updated April 26, 2026

Quick answer

A 10 × 10 ft slab at 4 inches thick needs about 56 bags of 80 lb concrete (33.3 ft³ ÷ 0.60 ft³/bag). With a standard 10% waste factor, buy 62 bags of 80 lb, 82 bags of 60 lb, or 123 bags of 40 lb. At ~1.4 cubic yards you're right on the edge where ordering ready-mix from a truck is cheaper, faster, and gives a stronger slab than mixing bags by hand.

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How the math works

A 10 × 10 slab at 4 inches is 10 × 10 × (4 ÷ 12) = 33.33 cubic feet. An 80 lb bag of pre-mixed concrete (Quikrete spec) yields 0.60 ft³, so you need 33.33 ÷ 0.60 ≈ 56 bags with no waste, and 62 bags with the standard 10% waste factor.

Formula

Bag count formula

bags = ceil( L × W × (T_in ÷ 12) × (1 + waste%) ÷ yield_per_bag )

L, W = slab in feet · T_in = thickness in inches
yield_per_bag (ft³): 40 lb = 0.30 · 60 lb = 0.45 · 80 lb = 0.60

Always round up. A few extra bags cost less than driving back to the store with wet concrete already in your wheelbarrow. If you're buying from a different brand than Quikrete, check the actual yield on the bag, Sakrete and Maximizer have slightly different specs.

10 × 10 ft slab, bag count by thickness (with 10% waste)

Thickness	Volume	40 lb bags	60 lb bags	80 lb bags	Cubic yards
3 in	25.0 ft³	92	62	46	0.93
4 in	33.3 ft³	123	82	62	1.23
5 in	41.7 ft³	153	102	77	1.54
6 in	50.0 ft³	184	123	92	1.85
8 in	66.7 ft³	245	163	122	2.47

Worked example

10 × 10 shed pad at 4 inches (80 lb bags)

Standard backyard shed base. Quikrete 80 lb bags, 10% waste factor.

1. Volume = 10 × 10 × (4/12)33.33 ft³
2. + 10% waste36.67 ft³
3. Bags = 36.67 ÷ 0.6061.1
4. Round up62 bags

→ Buy 62 × 80 lb bags, or 1.5 yards of ready-mix.

Worked example

Same slab, but 6 inches (e.g. driveway pad)

6-inch reinforced slab for a single-car parking pad.

1. Volume = 10 × 10 × (6/12)50.0 ft³
2. + 10% waste55.0 ft³
3. Bags = 55.0 ÷ 0.6091.7
4. Round up92 bags

→ 92 × 80 lb bags is 7,360 lb of dry mix, call the truck instead.

When should I order ready-mix instead?

At 1 cubic yard or more (~45 bags of 80 lb), ready-mix from a concrete truck almost always wins on cost, time, and consistency. A 10 × 10 × 4-inch pad is right on that threshold, anything thicker and you should be on the phone with a mix supplier. Most ready-mix companies have a 1-yard minimum with a "short-load" fee of $50–$120; you'll still save money and a weekend over mixing 60+ bags.

Bagged vs ready-mix, true cost on a 10 × 10 × 4 in slab

Approach	Materials	Tools	Time (1–2 people)	Typical total
62 × 80 lb bags by hand	$310 ($5/bag)	Wheelbarrow, hoe	8–12 hr + cleanup	$310
62 bags + rented mixer	$310	+$60 mixer rental	5–7 hr	$370
1.5 yd³ ready-mix delivered	$300–$450 + short fee	Wheelbarrow only	1.5 hr to place	$350–$500

Can I mix 62 bags by hand in one day?

Yes, with a power mixer and 2–3 people. Without a mixer, plan on a full weekend and accept that the early batches will be set before the last ones go in, which means cold joints in your slab, weak seams that crack under load. For a single continuous pour over 1 yd³, rent a mixer or call the truck.

Common mistakes (and how to avoid them)

✗ Buying exactly 56 bags (the raw math) and running short.

Fix: Always add 10% waste minimum. Round up. Returning unopened bags is easy; mid-pour panic is not.

✗ Skipping the 4-inch compacted gravel base under the slab.

Fix: Excavate 8 inches total: 4 in of compacted ¾-in crushed stone + 4 in of concrete. Slabs poured directly on dirt always crack.

✗ Pouring 60+ bags by hand in one session with no mixer.

Fix: Either rent a mixer, recruit help, or call ready-mix. Concrete waits for no one, first batches set in 60–90 minutes.

✗ Skipping control joints in a slab over 100 sqft.

Fix: Saw-cut joints 1/4 of the slab depth, every 8–10 ft, within 24 hours of the pour. Cracks will go where you cut, not where they want to.

→ Run the exact bag count for your slab in the concrete calculator

Frequently asked questions

How many 80 lb bags for a 10×10 slab at 4 inches?

62 bags including a 10% waste factor (56 bags raw). The slab is 33.3 cubic feet of concrete and an 80 lb bag yields 0.6 ft³.

How many 60 lb bags for the same 10×10 slab?

About 82 bags of 60 lb (with 10% waste). 60 lb bags yield 0.45 ft³ each, so the math is 36.67 ÷ 0.45 = 81.5 → 82 bags.

How many 40 lb bags for a 10×10 slab?

About 123 bags of 40 lb at 4 inches deep. At that count, 40 lb bags only make sense if you can't lift heavier ones, the per-yard cost is significantly higher.

How many cubic yards is a 10×10×4 slab?

1.23 cubic yards (1.36 with waste). At that volume, ready-mix from a truck is usually cheaper than mixing 62 bags by hand once you factor in your time.

Should I use 4-inch or 6-inch thickness?

4 inches is standard for sheds, patios, and walkways. Go to 6 inches for driveways, garages, or anything that holds vehicles. A 10×10 driveway pad at 6 inches needs 92 bags of 80 lb.

What's the cheapest way to pour a 10×10 slab?

Ready-mix at 1.5 yards is typically $300–$450 delivered (plus short-load fee). 62 × 80 lb bags at ~$5 each runs $310 plus the labor of mixing. Ready-mix wins on time; bags win only if you can't get a truck to the site.

How long does a 10×10 slab take to cure?

Walkable in 24–48 hours, drivable in 7 days, full strength at 28 days. Keep it damp for the first 7 days (mist with a hose or cover with plastic), proper curing makes a 30% difference in final strength.

How many 80 lb bags of concrete for a 10×10 slab?

How the math works

Bag count formula

10 × 10 shed pad at 4 inches (80 lb bags)

Same slab, but 6 inches (e.g. driveway pad)

When should I order ready-mix instead?

Can I mix 62 bags by hand in one day?

Common mistakes (and how to avoid them)

Frequently asked questions

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