Sakrete Calculator

Q: How much area does one bag of concrete cover?

It depends on how thick you pour. At 4 inches thick: 80 lb bag: about 1.8 square feet 60 lb bag: about 1.35 square feet 40 lb bag: about 0.9 square feet Pour it 6 inches thick and each bag covers about a third less area.

Sakrete Calculator

Updated Aug 15, 2026 By Jehan Wadia

Introduction

This Sakrete concrete calculator tells you how many bags of mix you need for your job. Type in your length, width, and depth. The tool does the math and shows the bag count right away.

It covers 17 project types. You can plan a slab, patio, driveway, footing, post hole, deck footing, curb, or set of stairs. You can also figure out slab repair, resurfacing, floor leveling, asphalt patch, stucco, stone veneer mortar, brick and block mortar, wall coating, and sand or gravel fill.

Pick your bag size — 40 lb, 50 lb, 60 lb, or 80 lb — and compare all four at once. The calculator also gives you the volume in cubic feet, cubic yards, and cubic meters. It adds a waste buffer so you do not run short, and it can show your total cost if you enter a price per bag. For wet mixes, it even tells you about how much water to add.

Every answer comes with a step-by-step solution, so you can see exactly how the numbers work. Use the quick presets for common jobs, or enter your own sizes in feet, inches, yards, meters, or centimeters. Buy the right amount of concrete the first time, and skip the extra trip to the store. If you use a different brand, try our Quikrete Calculator, or start with the general Concrete Calculator.

How to use our Sakrete Concrete Calculator

Pick your project type, type in your measurements, and the concrete calculator tells you how many bags of mix you need, plus the volume in cubic yards, cubic feet, and cubic meters, the water needed, and your cost.

Jump to Calculator: Choose your project from the drop-down list, like a slab pour, post hole, footing, stairs, stucco, or sand and gravel. The page scrolls right to that calculator.

Quick presets: Click a preset button, such as Sidewalk or Fence Post, to fill in common sizes fast. You can still change any number after.

Length, Width, Diameter, and Height: Type the size of your project area. Use the drop-down next to each box to pick feet, inches, yards, meters, or centimeters. If you only know the floor area, the Square Footage Calculator and the Feet and Inches Calculator can help you get there.

Thickness or Depth: Type how deep the pour will be, or tap a quick button like 4 in or 6 in. Slabs need at least 2 inches.

Number of Footings, Holes, or Steps: Type how many of the same shape you are pouring. Use whole numbers only, and at least 1.

Coat System, Unit Type, or Material Type: On stucco, masonry, and aggregate calculators, pick your option. This sets how much mortar, stucco, or stone you need per square foot.

Waste Buffer (%): Add extra material for spills and uneven ground. We start at 10%, and you can set anything from 0% to 30%.

Price Per Bag ($): Type what one bag costs to see your total cost. Leave it blank to skip cost.

Select Your Bag Size: Click 40 lb, 60 lb, or 80 lb to see bag counts for that size. The chart and table still show all four bag sizes so you can compare.

Calculate and Reset: Results update as you type, but you can click Calculate to check your work. Click Reset to Defaults to start over.

Concrete Bag Mix: What You Need to Know

Bagged concrete is dry mix in a sack. It holds cement, sand, and small stones. You add water, stir it, and pour it. It is the easy way to do small jobs like a patio, a fence post, a step, or a patch. Big jobs, like a full driveway, may be cheaper with a ready-mix truck — check the totals with our Concrete Volume Calculator and Cubic Yard Calculator first.

How Bag Counts Work

Every job starts with volume. You find how much space you must fill in cubic feet, then divide by how much wet mix one bag makes. That amount is called the yield. Here are the common yields for standard concrete mix:

40 lb bag — about 0.30 cubic feet
50 lb bag — about 0.375 cubic feet
60 lb bag — about 0.45 cubic feet
80 lb bag — about 0.60 cubic feet

It takes 45 bags of 60 lb mix or about 45 bags of 80 lb mix to make one cubic yard, so plan ahead. One cubic yard equals 27 cubic feet, which you can double-check with the Cubic Feet Calculator. Mortar, stucco, and resurfacer bags yield less than plain concrete mix, because the mixes are different — see the Mortar Calculator for wall work.

Why You Buy Extra

Never buy the exact count. Some mix sticks in the wheelbarrow. Some spills. Holes in the ground are often wider than you dug them. A waste buffer of 5% to 10% is normal. For post holes and rough dirt, go closer to 10% or 15%. Always round up to a whole bag.

Common Thickness Rules

Slabs and patios: 4 inches thick is standard. Use 5 to 6 inches where cars or trucks drive. The Concrete Slab Calculator covers flat pours in detail.
Footings: Depth depends on your local frost line. Check your building code, then size the pour with the Concrete Footing Calculator or, for round tube forms, the Sonotube Calculator.
Post holes: Dig about three times the post width, and one third of the post length deep. Plan the whole line with the Fence Calculator.
Patch repair: Keep repairs under 6 inches deep, and clean out all loose bits first. For pavement work, the Asphalt Calculator helps with cold patch volume.
Resurfacer: Thin coats only, up to about 2 inches.

Water and Mixing

Water amount matters a lot. An 80 lb bag of concrete mix needs about 3 quarts of water. Too much water makes weak, cracky concrete. Add water slowly and stop when the mix looks like thick oatmeal. Check the bag label, since each product is a little different.

Sand and Gravel

Loose stone and sand are sold by weight, not by yield. Sand weighs about 100 pounds per cubic foot. Gravel is close to 105. Pea gravel is near 96. So a 50 lb bag of sand fills about half a cubic foot. Big fill jobs are often cheaper by the ton from a yard — price them out with the Sand Calculator, Gravel Calculator, Pea Gravel Calculator, or Crushed Stone Calculator.

Quick Tips for a Better Pour

Pour on a firm, packed base. Soft dirt leads to cracks. Use the Excavation Calculator to size your dig.
Mix and pour on the same day. Do not save wet mix.
Pour when it is between 50°F and 90°F if you can.
Keep new concrete damp for a few days so it cures strong.
Add control joints in slabs so cracks happen in straight, hidden lines, and lay out steel with the Rebar Calculator.
Wear gloves, eye guards, and a dust mask. Dry cement burns skin.

Related Construction Calculators

Concrete Block Calculator — count CMU units for a wall.
Brick Calculator — brick counts and mortar for veneer or garden walls.
Paver Calculator — patio and walkway pavers with base material.
Retaining Wall Calculator — block, base, and backfill for retaining walls.
Stair Calculator and Stair Stringer Calculator — rise, run, and layout before you pour steps.
Concrete Weight Calculator — total weight of your finished pour.
Square Yard Calculator — convert areas for material orders.

Formulas used

Rectangular volume (slab, footing, repair area)

V = L \times W \times T

Circular slab / cylindrical hole volume

V = \pi \left(\frac{D}{2}\right)^2 T

Stair (stacked prism) volume for N steps

V = W \times H \times R \times \frac{N(N+1)}{2}

Curb and gutter barrier volume

V = R \times t \times (G + H)

Total volume with waste buffer

V_{adj} = V_{unit} \times N \times \left(1 + \frac{w}{100}\right)

Bags needed for a given bag size

N_{bags} = \left\lceil \frac{V_{adj}}{y_{bag}} \right\rceil

Bag yield and total weight for loose aggregate (density based)

y_{bag} = \frac{S}{\rho}, \qquad M = V_{adj} \times \rho

Estimated mixing water

W = N_{bags} \times \left(\frac{S}{60} \times 0.5625\right)

Frequently asked questions

How many bags of Sakrete concrete do I need for a 10 ft x 10 ft slab?

A 10 ft x 10 ft slab at 4 inches thick is 33.3 cubic feet. With a 10% waste buffer, that is about 36.7 cubic feet. That works out to:

80 lb bags: 62
60 lb bags: 82
40 lb bags: 123

That is a lot of mixing. For a job this size, price out a ready-mix truck too.

How many bags make one cubic yard?

One cubic yard is 27 cubic feet. Using standard concrete mix yields:

80 lb bags: 45
60 lb bags: 60
50 lb bags: 72
40 lb bags: 90

The calculator shows your cubic yards next to the bag count, so you can compare bags to a truck order fast.

How much area does one bag of concrete cover?

It depends on how thick you pour. At 4 inches thick:

80 lb bag: about 1.8 square feet
60 lb bag: about 1.35 square feet
40 lb bag: about 0.9 square feet

Pour it 6 inches thick and each bag covers about a third less area.

Why is the bag count always rounded up?

You cannot buy half a bag at the store. If the math says 61.1 bags, the tool shows 62. Running short in the middle of a pour leaves a cold joint, which is a weak spot. It is always better to have one extra bag left over.

Why can I only pick 40 lb, 60 lb, and 80 lb bags?

Those three buttons are the sizes most stores carry. But the All bag sizes row and the bar chart still show the 50 lb count. So you get all four numbers every time, no matter which button you press.

Do mortar, stucco, and resurfacer bags hold the same amount as concrete bags?

No. Those mixes are finer and yield less. This calculator already uses the right yield for each job type:

Concrete mix, 80 lb: about 0.60 cubic feet
Mortar, stucco, resurfacer, 80 lb: about 0.54 cubic feet
Asphalt cold patch, 80 lb: about 0.53 cubic feet

You do not need to change anything. Just pick the right project type.

Does the post hole calculator subtract the space the post takes up?

No. It fills the whole hole. That extra mix acts as a built-in buffer, since holes are almost always wider at the top than you planned. If you want a tighter number, drop your waste buffer to 0%.

Why do stairs need so much concrete?

Steps stack on top of each other. The bottom step holds up every step above it, so it is the deepest. The tool uses the stacked formula, so 3 steps take 6 times one step block, not 3 times. That is why the bag count jumps fast when you add steps.

What if my patio or slab is not a rectangle?

Break it into simple shapes. Run the slab calculator for each rectangle, then add the bag counts together. For round parts, use the Circular Slab calculator. Add the totals at the end, then round up.

Why won't the slab calculator take a thickness under 2 inches?

Concrete thinner than 2 inches cracks and breaks apart under weight. If you only want a thin skim over old concrete, use the Resurfacing calculator instead. It is built for coats up to 2 inches.

Why does slab repair stop at 6 inches deep?

Patch products are made for shallow fixes. If the damage is deeper than 6 inches, you are really replacing a section. Use the Slab Pour calculator and regular concrete mix for that.

Which stucco coat system should I pick?

Pick the one that matches your wall build:

1-coat: about 3/8 inch total, over foam board
2-coat: about 1/2 inch total, over solid block or brick
3-coat: about 7/8 inch total, over lath and paper

3-coat uses the most material, so it gives the highest bag count.

Which unit type should I choose for masonry mortar?

Pick the block or brick you are laying. Each one uses a different amount of mortar per square foot of wall:

Standard brick: 0.055 cubic feet per sq ft (most joints)
CMU 8 in block: 0.035 cubic feet per sq ft
CMU 12 in block: 0.052 cubic feet per sq ft

Why is there no water estimate for sand, gravel, or asphalt patch?

Those materials do not get mixed with water. Loose sand and stone go in dry. Cold patch comes ready to shovel and tamp. The water line only shows up for mixes you have to wet down, like concrete, mortar, and stucco.

How many bags of sand or gravel fill one cubic yard?

Loose stone is sold by weight, not yield. One cubic yard of sand weighs about 2,700 lb. That is about 54 bags at 50 lb each, or 34 bags at 80 lb. The calculator also shows your total in tons, so you can compare bag price to bulk price by the ton.

Can I enter my sizes in meters or centimeters?

Yes. Every measurement box has a unit menu with feet, inches, yards, meters, and centimeters. You can even mix them, like length in meters and depth in inches. Under each box you will see the value in meters, and your results include cubic meters.

How accurate is the bag count?

It is a close estimate, not a promise. Real yield shifts with how wet you mix, how much sticks to the wheelbarrow, and how even your base is. Your dig is also never perfect. That is why the waste buffer starts at 10%. Always check the yield printed on the bag before you buy.

Does the estimate include rebar, gravel base, or forms?

No. This tool counts bags of mix only. You still need to plan wire mesh or rebar, a packed gravel base, form boards, stakes, and a sealer. Price those out on top of your bag cost.

When should I skip bags and order a ready-mix truck?

Once you pass about 1 cubic yard, or roughly 45 to 60 bags, mixing by hand gets very slow. Two people can mix maybe 20 bags an hour with a mixer. Past that point, a truck is usually faster and often cheaper per yard. Most yards do charge a small-load fee.

What waste buffer should I set?

Use 5% for a clean pour inside tight forms. Use 10% for most slabs and footings. Use 15% for post holes, rough dirt, or repair work where the edges are broken. You can set anything from 0% to 30%.

Can I print or save my results?

There is no save button, but you can press Ctrl+P (or Cmd+P on a Mac) to print the page or save it as a PDF. The step-by-step solution prints too, so you can take the math and the bag list to the store.

How much water does each bag need?

Roughly 3 quarts for an 80 lb bag, a bit over 2 quarts for a 60 lb bag, and about 1.5 quarts for a 40 lb bag. The calculator adds it up in gallons and quarts for your whole job. Add water slowly and stop when the mix looks like thick oatmeal. Extra water means weak concrete.

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