This concrete bag calculator estimates the exact number of 80 lb, 60 lb, 50 lb, or 40 lb bags required for slabs, post holes (with post displacement), footings, or custom projects. Accounts for waste buffer, estimates total dry weight, mixing water, material cost, and ready-mix truck delivery limits.
Reviewed and updated June 30, 2026
Use it when you want to know
Slab, Footing, & Hole CalculationsInput dimensions for rectangular/circular slabs, post holes, or concrete piers.
Post Displacement CorrectionAutomatically subtracts post volume to prevent buying too much concrete.
Transport Weight & Water AdviceSee total weight in lbs/tons to check vehicle payload, plus total mixing water needed.
Calculator
Estimate concrete bags & cost
Select your project type, enter your dimensions, and select a bag size preset to compute the total bags, weight, water requirements, and estimated project cost.
Guide
How to calculate concrete bags for home projects
Estimating concrete correctly is crucial. If you buy too little, you risk having a dry "cold joint" on your slab while you run back to the store. If you buy too much, you are stuck hauling back hundreds of pounds of heavy bags. You can also use our Cubic Yard Calculator or Square Footage Calculator to quickly calculate project volumes before converting them to bag counts.
What is the standard concrete bag yield?
Concrete yields represent the volume of wet, mixed concrete produced by one bag. Density varies slightly by mix type, but these standard approximations are used by manufacturers like Quikrete and Sakrete for their standard concrete mixes:
80 lb bag: 0.60 cubic feet yield. You need 45 bags to make 1 cubic yard.
60 lb bag: 0.45 cubic feet yield. You need 60 bags to make 1 cubic yard.
50 lb bag: 0.375 cubic feet yield. You need 72 bags to make 1 cubic yard.
40 lb bag: 0.30 cubic feet yield. You need 90 bags to make 1 cubic yard.
How does post displacement affect post hole concrete?
Setting fence or deck posts in concrete requires pouring concrete around a wooden or metal post placed inside a dug hole.
A common DIY mistake is calculating the full cylinder volume of the hole and buying that amount of concrete. However, the wood post itself displaces a significant portion of that volume. Our calculator automatically subtracts this post displacement based on the actual (not nominal) dimensions of the post:
A 4x4 wood post has actual dimensions of 3.5 inches × 3.5 inches.
A 6x6 wood post has actual dimensions of 5.5 inches × 5.5 inches.
For a 3-foot (36 inch) deep hole, a 4x4 post displaces about 0.25 cubic feet of concrete, saving you nearly half a bag of 80 lb concrete per hole!
When should you choose ready-mix vs. bagged concrete?
A single cubic yard of concrete is 27 cubic feet. Hauling and mixing 45 bags of 80 lb concrete (or 60 bags of 60 lb concrete) is the practical limit for most homeowners.
If your project is larger than 1 cubic yard, consider renting a towable mixer (which usually yields 3–9 bags per mix), having bags delivered on a pallet rather than hauling in a passenger car, or ordering ready-mix delivery from a truck.
How much water is needed to mix a bag of concrete?
Using too much water makes concrete easy to pour but significantly weakens it. Standard 80 lb bags should use no more than 3 quarts (6 pints) of water.
The concrete should have the consistency of thick oatmeal or moldable clay. If it is runny or soupy, the cured strength (PSI) could drop by up to 50%, leading to early cracking and crumbling.
What are the limits for hauling concrete bags in a vehicle?
Dry concrete mix is extremely heavy. A standard midsize SUV or passenger car has a cargo payload capacity of 850 to 1,000 lbs (including passengers). Hauling just twelve 80 lb bags (960 lbs) can fully load your vehicle.
A standard half-ton pickup truck has a payload limit of 1,500 to 2,000 lbs. If your total project weight exceeds 1,000 lbs, we highly recommend utilizing store delivery or making multiple trips to protect your suspension.
FAQ
Frequently asked questions
How many 80 lb bags of concrete are in a cubic yard?
An 80 lb bag of concrete yields approximately 0.60 cubic feet of mixed concrete. Since a cubic yard is 27 cubic feet, you need exactly 45 bags of 80 lb concrete to make one cubic yard.
How many 60 lb bags of concrete are in a cubic yard?
A 60 lb bag of concrete yields about 0.45 cubic feet of mixed concrete. To make one cubic yard (27 cubic feet), you will need exactly 60 bags of 60 lb concrete.
What is the ready-mix truck threshold vs. buying bags?
Generally, if your project requires 1 cubic yard (45 bags of 80 lb, or 60 bags of 60 lb) or more, ordering a ready-mix delivery truck becomes highly recommended. Mixing 45+ bags by hand or small mixer is extremely labor-intensive. Keep in mind that ready-mix suppliers charge short-load surcharges for deliveries under 3 to 5 cubic yards, so always compare total costs.
How much water do you mix with an 80 lb concrete bag?
A standard 80 lb bag of concrete mix requires approximately 6 pints (3 quarts, or 2.8 liters) of clean water. It is best to start with 5.5 pints and add the remaining water gradually only if necessary to achieve a thick, moldable clay-like consistency.
Do post holes require subtracting the post volume?
Yes. When you place a post (like a 4x4 or 6x6 wood timber) inside a hole, the wood displaces concrete. For example, a 4x4 post (which actually measures 3.5" x 3.5") submerged 36 inches displaces about 0.25 cubic feet of volume. Subtracting this displacement from the total hole volume ensures you do not buy unnecessary bags.
What is the standard payload capacity for hauling concrete bags?
A typical midsize SUV or passenger car has a cargo payload capacity of 850 to 1,000 lbs (including passengers). Hauling just twelve 80 lb bags of concrete (960 lbs) can fully load your vehicle. A standard half-ton pickup truck (F-150, Silverado) has a payload limit of 1,500 to 2,000 lbs. If your project weight exceeds 1,000 lbs, consider home delivery or multiple trips to prevent vehicle suspension damage.