Sakrete Calculator

This is an independent calculator. Sakrete is a trademark of its owner; we are not affiliated with or endorsed by Sakrete. The bag counts here use the yields in the Sakrete High-Strength Concrete Mix technical data sheet: 0.30 ft³ per 40 lb, 0.45 ft³ per 60 lb, 0.60 ft³ per 80 lb and 0.66 ft³ per 90 lb bag. Other Sakrete products can yield differently, so check the yield printed on your bag.

How many bags of Sakrete do I need?

Divide your volume in cubic feet by the yield per bag and round up. Sakrete High-Strength Concrete Mix yields 0.60 ft³ per 80 lb bag (per its data sheet), so 16 ft³ of concrete needs 27 bags.

Bags = volume (ft³) ÷ yield per bag (from the bag label), rounded up

These yields come from the Sakrete High-Strength Concrete Mix data sheet. The 40, 60 and 80 lb yields match QUIKRETE Concrete Mix, but Sakrete’s 90 lb bag yields 0.66 ft³ (Quikrete’s yields 0.675 ft³), so 1 yd³ takes 41 Sakrete 90 lb bags against 40 Quikrete. If your bag lists a different yield, divide your volume by that number instead. Specialty mixes such as fast-setting products may yield differently.

Sakrete bags for common slab sizes

These counts assume 0.60 ft³ per 80 lb bag and 0.45 ft³ per 60 lb bag, at 4 in thick. The second number adds 10% for waste.

At 6 in thick, a 10 × 10 ft slab needs 84 × 80 lb bags and a 12 × 12 ft slab needs 120. In metric, a 3 × 3 m slab 10 cm thick (0.9 m³) needs 53 × 80 lb bags.

Reading the label correctly saves a recount at the store. The yield is usually printed in cubic feet, sometimes with litres alongside. Divide your volume by that number, not by the bag weight. If the label gives only litres, divide by 28.32 to get cubic feet: 17 L is 0.60 ft³. Then enter your dimensions above and compare the result with the count at the label yield. The difference matters most on large pours: on a 12 × 12 ft slab, every 0.01 ft³ of yield changes the count by more than one bag.

Sakrete calculator for a slab, step by step

Most recounts at the store come from a measurement taken once and trusted. This order of work gets a count you can buy against:

1. Measure the inside of the forms, not the outside of the boards. A 10 × 12 ft form built from 2× lumber measures 3 in less each way on the inside if you measure outside edges by mistake.
2. Measure depth in at least five spots: each corner and the middle. Use the average. On a 12 × 12 ft slab, an average depth of 4½ in instead of 4 in raises the count from 80 to 90 × 80 lb bags.
3. Enter length and width in feet and thickness in inches in the calculator above, with your waste setting.
4. Read the yield on the Sakrete bag you will buy and, if it is not 0.60 ft³ per 80 lb bag, divide the calculator’s cubic feet by it.
5. Round up once, at the end. A 10 × 12 ft slab at 4 in is 40 ft³: 66.7 bags becomes 67, and 73.3 with 10% extra becomes 74.

Sakrete in metric and kilogram bags

Outside the US, bagged concrete is often sold by the kilogram, and the label states the yield in litres. Work in litres throughout: 1 m³ is 1,000 L, so a 3 × 3 m slab 10 cm thick is 0.9 m³, or 900 L. Divide by the litres per bag on your label and round up. At 17 L per bag (the Sakrete data-sheet 80 lb yield) that is 53 bags; at 12.7 L per bag it is 71. If the label gives kilograms only and no yield, ask the retailer for the product data sheet before you buy, because a count based on weight alone is a guess.

What if your Sakrete bag lists a different yield?

Use the label figure; the count moves more than most people expect. The table shows how an 80 lb bag’s yield changes the count for two common slabs and for one cubic yard.

These are exact counts before the 10% waste allowance. A label that reads 0.50 ft³ instead of 0.60 ft³ adds 16 bags to a 12 × 12 ft slab, which is a second trip to the store if you did not check. The calculator above uses 0.60 ft³; if your label differs, divide the cubic feet it reports by your label yield instead of using its bag count.

Some labels state coverage as square feet at a given thickness instead of a volume. Multiply the square feet by the thickness in inches and divide by 12 to get the yield in cubic feet: 1.8 ft² at 4 in is 1.8 × 4 ÷ 12 = 0.60 ft³.

How much Sakrete for posts and Sonotubes?

A post hole is a cylinder minus the post. At Sakrete data-sheet yields, one hole takes:

For a fence line, multiply the exact volume by the number of posts and round once at the end. The fence post concrete calculator handles hole width, depth and post size.

Sakrete for 6 inch slabs

A 6 in slab takes 1.5 times the concrete of a 4 in slab. At Sakrete data-sheet yields:

Which thickness you need depends on the load and your local code, so settle that before you count bags. Every row from 8 × 8 ft down the table is over a cubic yard, the point where most people price a ready-mix truck alongside bags.

Sakrete bags per square foot and per square metre

If you know the area rather than the dimensions, divide it by the coverage of one bag. At the Sakrete data-sheet yield of 0.60 ft³ an 80 lb bag covers about 1.8 ft² at 4 in thick, 2.4 ft² at 3 in and 3.6 ft² at 2 in. A 60 lb bag covers 1.35 ft² at 4 in.

That puts 100 ft² at 4 in at 56 × 80 lb bags (62 with 10% extra), 200 ft² at 112 (123), and 500 ft² at 278 (306). By the time you pass 100 ft² you are over a cubic yard, so a ready-mix quote is worth getting.

Small pads are where bags shine. At 4 in thick:

• 2 × 2 ft (a step landing or AC pad base): 1.33 ft³, 3 × 80 lb bags.
• 3 × 3 ft: 3 ft³, 5 × 80 lb bags, or 6 with 10% extra.
• 3 × 6 ft: 6 ft³, 10 × 80 lb bags, or 11 with extra.
• 5 × 5 ft: 8.33 ft³, 14 × 80 lb bags, or 16 with extra.

In metric, one square metre takes 3 × 80 lb bags at 5 cm, 5 at 7.5 cm, 6 at 10 cm and 9 at 15 cm. Where Sakrete is sold in kilogram bags, the label yield in litres is the number to divide by: 1 m³ is 1,000 L.

40 lb or 80 lb Sakrete bags: which size to buy?

Buy by the job, not the price per bag. At the data-sheet yields the dry weight per cubic foot is the same for every bag size, so 56 × 80 lb bags and 112 × 40 lb bags for a 10 × 10 ft slab both weigh 4,480 lb. What changes is how many times you lift, open and empty a bag.

• 80 lb bags suit slabs and anything over about 10 ft³: half the bags to handle, half the bag-opening time.
• 60 lb bags are a middle ground if 80 lb is too heavy to lift safely; the same slab takes 75 of them.
• 40 lb bags suit post holes, repairs and pours you mix in a bucket. They also waste less: the last partial bag is at most 0.30 ft³ instead of 0.60 ft³.

On a 20-post fence with 4×4 posts in 10 in holes 2 ft deep, the total is 18.41 ft³: 31 × 80 lb bags or 62 × 40 lb bags. If one person is setting the posts alone, the lighter bag may be worth the extra trips.

Fast-setting and specialty Sakrete mixes

Bagged concrete brands, Sakrete included, often sell specialty products such as fast-setting mixes alongside standard concrete mix. This page quotes yields only for Sakrete High-Strength Concrete Mix, from its data sheet; we have not verified yields for the fast-setting or other specialty mixes, so it does not quote them. The method stays the same: read the yield in cubic feet (or litres, divided by 28.32) on the exact bag, divide your volume by it, and add your waste allowance. Products that you pour dry into a post hole and then add water to are measured the same way; only the mixing step differs, so follow the bag instructions for water.

Common mistakes when estimating Sakrete

• Assuming every Sakrete product yields the same. The 0.60 ft³ per 80 lb figure is from the Sakrete High-Strength Concrete Mix data sheet. Fast-setting and specialty mixes can differ, so read the yield on the exact bag before you multiply.

• Rounding each post hole. In the example above, rounding every hole to 2 bags gives 20 × 80 lb bags; totalling first gives 16. On a 20-post fence the total-first count is 31 bags.

• Mixing up bag sizes. A count of 56 is right for a 10 × 10 ft slab in 80 lb bags. In 60 lb bags the same 56 bags make only 25.2 ft³, about 24% short.

• Typing inches into a feet field. A 4 in slab entered as 4 ft makes a 10 × 10 ft pad 400 ft³ and 667 bags instead of 56.

• Skipping the waste allowance. A base that sits ½ in low over 100 ft² swallows 4.17 ft³, about 7 extra 80 lb bags. Keep 10% unless your forms are rigid and the base is level.

• Reading the label yield in the wrong unit. A yield of 17 L is 0.60 ft³, not 17 ft³. Dividing 33.33 ft³ by 17 suggests 2 bags for a 10 × 10 ft slab; the correct count is 56. Convert litres to cubic feet (÷ 28.32) or convert your volume to litres first.

• Measuring the outside of the forms. On a 10 × 12 ft slab, measuring 3 in too long each way adds about 1.85 ft³, roughly 3 extra 80 lb bags you then have to return.

Sakrete calculator vs related calculators: which one to use

Use this page when you plan to buy Sakrete and want counts at the yields on Sakrete’s High-Strength Concrete Mix data sheet (0.30, 0.45, 0.60 and 0.66 ft³ for 40, 60, 80 and 90 lb bags). For other questions:

• Quikrete calculator for QUIKRETE bags, including the 50 lb size and the 0.675 ft³ 90 lb yield.
• Concrete bag calculator to compare 40, 50, 60 and 80 lb bags for any brand.
• Bags of concrete per yard when you already have a volume in cubic yards.
• Fence post concrete calculator for a full fence line with a post count and hole size.

Sakrete bags or ready-mix?

Up to about ½ yd³ (23 × 80 lb bags, or 25 with 10% extra), bags are the simple choice. Between ½ and 1 yd³ you need 23 to 45 bags and a mixer helps. Above 1 yd³, ready-mix is usually less work and avoids cold joints between batches: a full yard in bags is 45 × 80 lb, 3,600 lb of dry mix to lift twice, once into the cart and once into the mixer.

To compare cost, multiply your bag count by your store’s price per bag and ask a local plant for a delivered quote. The concrete price per yard page explains what drives that quote.