How Much Concrete Do I Need for a 10×10 Slab?
A 10×10 ft slab at 4 in thick is 33.33 ft³ = 1.23 cubic yards. At 0.60 ft³ per 80-lb bag that is 56 bags before waste (62 with 10%). Use the Concrete Slab Calculator for your exact dimensions.
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The quick answer
A 10×10 ft slab is 100 ft². Volume = length × width × thickness: 10 × 10 × (4÷12) = 33.33 ft³ ÷ 27 = 1.23 yd³ before waste. With 10% waste you order about 1.36 yd³. Bag count at 0.60 ft³ per 80-lb bag: 33.33 ÷ 0.60 = 56 bags before waste, or 62 bags with 10%. That is past one cubic yard, so ready-mix delivery is usually cheaper than mixing ~60 bags by hand.
- 4 in thick — 33.33 ft³ = 1.23 yd³ (56 eighty-lb bags at 0.60 ft³) before waste; ~1.36 yd³ / 62 bags with 10%.
- 5 in thick — 41.7 ft³ = 1.54 yd³ (70 bags) before waste; ~1.70 yd³ / 77 bags with 10%.
- 6 in thick — 50.0 ft³ = 1.85 yd³ (84 bags) before waste; ~2.04 yd³ / 92 bags with 10%.
How thickness changes the number
Thickness is the single biggest driver of concrete volume, because it multiplies the entire 100 ft² footprint. Going from 4 in to 6 in adds 50% more concrete — and 50% more cost. Use 4 in for foot-traffic patios and shed pads, 5 in for heavy furniture or fire pits, and 6 in if the slab will ever see a vehicle.
Source: 1 cubic yard = 27 cubic feet. Thickness in inches ÷ 12 converts to feet.
10×10 at 4 in: 10 × 10 × (4÷12) = 33.33 ft³ ÷ 27 = 1.23 yd³. With 10% waste: 1.23 × 1.1 = 1.36 yd³ to order.
Bags vs. ready-mix delivery
Under about 1 cubic yard (~45 eighty-lb bags), bagged mix can be practical. A 10×10 at 4 in is already ~56 bags before waste — past that line for most DIYers — so ready-mix delivery is usually cheaper and far less labor. At 6 in you are over 2 yards. Schedule the truck and a crew of at least two ahead of time.
Base, forms and finishing tips
- Pour on 4–6 in of compacted gravel (3/4 in crushed stone with fines packs best).
- Set 2×4 forms level and staked every 3–4 ft; the slab is only as flat as the forms.
- Add wire mesh for a 4 in slab, or #4 rebar on 24-in centers for 5–6 in slabs.
- Cut control joints every 8–10 ft so the slab cracks where you want it to.
- Cure slowly — mist and cover with plastic for at least 7 days for full strength.
Frequently asked questions
How many bags of concrete do I need for a 10×10 slab at 4 inches?
33.33 ft³ ÷ 0.60 ft³ per bag = 56 eighty-pound bags before waste, or 62 bags with a 10% allowance. Confirm the yield on your bag label — brands vary slightly.
How many cubic yards is a 10×10 concrete slab?
1.23 yd³ at 4 in thick, 1.54 yd³ at 5 in, and 1.85 yd³ at 6 in — before waste. Add 10% for spillage and uneven subgrade.
Should I use bags or order ready-mix for a 10×10 slab?
At 4 in (about 1.2 yards) bags are workable with a mixer. At 5–6 in you are over 1.5 yards, where delivered ready-mix is usually cheaper and much less labor.
Calculators for this guide
Put these numbers to work with the free calculators referenced above.