How Many Bags of Concrete for a 10x10 Slab? Bag Yields and Waste
Quick answer: A 10 x 10 ft slab that is 4 inches thick needs about 62 bags of 80 lb concrete mix when you include a 10% waste allowance. That is 33.3 cubic feet (1.23 cubic yards) of concrete before waste and 36.7 cubic feet after. With 60 lb bags you need about 82, and with 40 lb bags about 123.
A 10 x 10 slab is one of the most common DIY pours: a shed floor, a small patio, an air conditioner pad. The math is simple, but small mistakes change the bag count by dozens. The free concrete calculator on RenoCalcs automates it, and this guide shows what it is doing. It is one of dozens of free home improvement calculators on the site.
The Formula
1. Volume = length x width x thickness (all in feet)
2. Order quantity = volume x (1 + waste % / 100)
3. Bags = order quantity / yield per bag, rounded up
For a 10 x 10 ft slab at 4 inches (0.333 ft):
• Volume: 10 x 10 x 0.333 = 33.3 cubic feet (1.23 cubic yards)
• With 10% waste: 36.7 cubic feet
Bag Yields
Typical yields per bag are about 0.60 cubic feet for 80 lb, 0.45 for 60 lb, and 0.30 for 40 lb. Yields vary by brand and mix, so check the label.
Bag size | Yield per bag | Bags for 36.7 cu ft
80 lb | about 0.60 cu ft | 62
60 lb | about 0.45 cu ft | 82
40 lb | about 0.30 cu ft | 123
Why Add Waste?
Ground is rarely perfectly level, forms leak a little, and the last wheelbarrow always comes up short. A 10% allowance is a sensible default. Running out mid-pour is worse than ending up with a few extra bags, because a pause can leave a weak joint. Order a little extra.
Measuring Thickness Accurately
Measure from the compacted base to the top of the form, and take several readings on uneven ground, then average them. If the slab will carry vehicles or structural loads, thickness requirements are different, so confirm with a qualified professional and local building codes.
Do You Need a Gravel Base?
Slabs are commonly poured over a compacted gravel base. For the same 10 x 10 ft footprint at 4 inches deep, a base needs about 1.23 cubic yards, or roughly 1.73 tons at 1.4 tons per cubic yard. With a 10% allowance that becomes about 1.9 tons. The gravel calculator rounds that figure up to the next tenth of a ton for ordering.
Irregular Shapes
Split L-shaped or odd slabs into rectangles, calculate each one, and add the results. Round footings and fence posts are better handled with a calculator built for them.
Bags or Ready-Mix?
Sixty-two bags of 80 lb mix is about 4,960 pounds to lift, open, and mix. Once a job passes roughly one cubic yard, or about 45 bags of 80 lb mix, compare ready-mix delivery. Ask about short-load fees, which can make a small ready-mix order cost more than expected.
Frequently Asked Questions
How many 80 lb bags of concrete for a 10 x 10 slab?
About 62 bags at 4 inches thick with a 10% waste allowance.
How much concrete does an 80 lb bag make?
About 0.60 cubic feet, though yields vary by brand.
Is it cheaper to buy bags or ready-mix?
Bags are fine for small jobs. Past about one cubic yard, compare ready-mix pricing, including delivery and short-load fees.
Before You Order
Measure twice, add your waste allowance, and read the bag label for the exact yield. Decide on bags or ready-mix before pouring day, and have the base and forms ready first. Remember that these figures are estimates, and structural work should be checked against local codes.
Quick answer: A 10 x 10 ft slab that is 4 inches thick needs about 62 bags of 80 lb concrete mix when you include a 10% waste allowance. That is 33.3 cubic feet (1.23 cubic yards) of concrete before waste and 36.7 cubic feet after. With 60 lb bags you need about 82, and with 40 lb bags about 123.
A 10 x 10 slab is one of the most common DIY pours: a shed floor, a small patio, an air conditioner pad. The math is simple, but small mistakes change the bag count by dozens. The free concrete calculator on RenoCalcs automates it, and this guide shows what it is doing. It is one of dozens of free home improvement calculators on the site.
The Formula
1. Volume = length x width x thickness (all in feet)
2. Order quantity = volume x (1 + waste % / 100)
3. Bags = order quantity / yield per bag, rounded up
For a 10 x 10 ft slab at 4 inches (0.333 ft):
• Volume: 10 x 10 x 0.333 = 33.3 cubic feet (1.23 cubic yards)
• With 10% waste: 36.7 cubic feet
Bag Yields
Typical yields per bag are about 0.60 cubic feet for 80 lb, 0.45 for 60 lb, and 0.30 for 40 lb. Yields vary by brand and mix, so check the label.
Bag size | Yield per bag | Bags for 36.7 cu ft
80 lb | about 0.60 cu ft | 62
60 lb | about 0.45 cu ft | 82
40 lb | about 0.30 cu ft | 123
Why Add Waste?
Ground is rarely perfectly level, forms leak a little, and the last wheelbarrow always comes up short. A 10% allowance is a sensible default. Running out mid-pour is worse than ending up with a few extra bags, because a pause can leave a weak joint. Order a little extra.
Measuring Thickness Accurately
Measure from the compacted base to the top of the form, and take several readings on uneven ground, then average them. If the slab will carry vehicles or structural loads, thickness requirements are different, so confirm with a qualified professional and local building codes.
Do You Need a Gravel Base?
Slabs are commonly poured over a compacted gravel base. For the same 10 x 10 ft footprint at 4 inches deep, a base needs about 1.23 cubic yards, or roughly 1.73 tons at 1.4 tons per cubic yard. With a 10% allowance that becomes about 1.9 tons. The gravel calculator rounds that figure up to the next tenth of a ton for ordering.
Irregular Shapes
Split L-shaped or odd slabs into rectangles, calculate each one, and add the results. Round footings and fence posts are better handled with a calculator built for them.
Bags or Ready-Mix?
Sixty-two bags of 80 lb mix is about 4,960 pounds to lift, open, and mix. Once a job passes roughly one cubic yard, or about 45 bags of 80 lb mix, compare ready-mix delivery. Ask about short-load fees, which can make a small ready-mix order cost more than expected.
Frequently Asked Questions
How many 80 lb bags of concrete for a 10 x 10 slab?
About 62 bags at 4 inches thick with a 10% waste allowance.
How much concrete does an 80 lb bag make?
About 0.60 cubic feet, though yields vary by brand.
Is it cheaper to buy bags or ready-mix?
Bags are fine for small jobs. Past about one cubic yard, compare ready-mix pricing, including delivery and short-load fees.
Before You Order
Measure twice, add your waste allowance, and read the bag label for the exact yield. Decide on bags or ready-mix before pouring day, and have the base and forms ready first. Remember that these figures are estimates, and structural work should be checked against local codes.