Sakrete Bag Calculator
Find out exactly how many bags of Sakrete to buy. Enter your slab or post-hole dimensions, pick the bag size, and this Sakrete bag calculator returns the bags needed (with 10% waste), the water required per Sakrete’s specs, the total weight, and the material cost.
Yields and water amounts are Sakrete’s published specs for High-Strength Concrete Mix; field yield varies with water content and placement. Add water gradually: excess water weakens the concrete.
Worked example, checked against this exact tool
10 x 10 ft slab, 4 inches thick, 80-lb bags at $6.50 each: volume = 10 x 10 x (4/12) = 33.33 cu ft. Bags = 33.33 / 0.60 = 55.56, rounded up to 56 bags. With 10% waste: 62 bags. Total weight = 62 x 80 = 4,960 lbs (about 2.5 tons: plan the haul). Water = 62 x 4 quarts = 248 quarts (62 gallons). Material cost = 62 x $6.50 = $403.00.
Sakrete yield per bag
Sakrete’s published yields for High-Strength Concrete Mix: a 40-lb bag makes 0.30 cu ft, 60-lb makes 0.45, 80-lb makes 0.60, and 90-lb makes 0.68. Divide your project’s cubic feet by the yield and always round up: a half bag of mixed concrete is useless, and running short mid-pour creates a cold joint. Field yield varies slightly with water content and placement, which is why the calculator adds 10% for waste, spillage, and uneven excavation.
Water: how much and how
Per Sakrete’s specs: 2 quarts per 40-lb bag, 3 per 60-lb, 4 per 80-lb, 4.5 per 90-lb. Add the water gradually and mix thoroughly; the finished mix should be workable but not soupy. Excess water is the most common DIY mistake: it makes mixing easier and the concrete weaker, cutting strength and inviting cracks. In hot weather use cold water to slow the set; in cold weather use warm water to speed it.
Post holes: the fence-post math
Bagged concrete’s most common job is setting posts. A 12-inch-diameter hole 36 inches deep holds pi x (0.5 ft)^2 x 3 ft = 2.36 cu ft, which takes 6 bags of 60-lb mix per hole. Switch the calculator to post-hole mode, enter diameter, depth, and hole count, and it totals the job. Rule of thumb: the hole should be three times the post’s width and a third of the post’s above-ground height deep.
Which mix and how thick
High-Strength Concrete Mix (4,000 psi at 28 days) suits slabs, footings, and posts at 2 inches thick and up. Fast-setting mixes trade working time for speed on posts and repairs. Sand mix is for thin applications under 2 inches. Minimum practical slab thickness is 4 inches for walkways and patios; driveways want 5 to 6. Cure by keeping the surface damp for several days; foot traffic is fine after about 24 hours, vehicles after 72.
What competing calculators miss
The dedicated rival covers slabs and post holes but stops at the bag count: no water, no cost, no 90-lb option. This page adds Sakrete-spec water quantities, total haul weight, and material cost, with the yield table and strength specs on the page so you can verify every number.
Frequently asked questions
How many bags of Sakrete do I need for a 10×10 slab?
At 4 inches thick: 33.33 cu ft / 0.60 = 56 bags of 80-lb mix, or 62 with 10% waste. Thicker slabs scale up proportionally.
How much concrete does an 80 lb bag of Sakrete make?
About 0.60 cubic feet of finished concrete when mixed per the directions.
How much water per bag of Sakrete?
2 quarts (40-lb), 3 quarts (60-lb), 4 quarts (80-lb), 4.5 quarts (90-lb). Add gradually; excess water weakens concrete.
How many 60 lb bags of concrete in a cubic yard?
A cubic yard is 27 cu ft; at 0.45 cu ft per bag that is exactly 60 bags. For 80-lb bags it is 45.
Should I use 60 lb or 80 lb bags?
80-lb bags cost less per cubic foot and mean fewer bags to haul, but each weighs 80 lbs: choose 60-lb if you are carrying them far or working alone.
How deep should a post hole be?
About one-third of the post’s above-ground height, and three times the post’s width in diameter. Below the frost line in cold climates.
Can I mix Sakrete in a wheelbarrow?
Yes for small jobs: a wheelbarrow or mortar pan works for a few bags; rent a mechanical mixer beyond that.
How long before I can walk on it?
Foot traffic after about 24 hours, vehicle traffic after about 72 hours, full strength at 28 days. Weather affects timing.
What is Sakrete Maximizer?
A high-yield lightweight mix: an 80-lb bag yields about 0.92 cu ft (vs 0.60 standard) at 5,500 psi. Fewer bags for the same volume.
How do I estimate waste?
Add 10% for spillage, uneven excavation, and grade variation. This calculator includes it in the recommended count.