Estimate how many batches an on-site concrete mixer must produce for a measured pour. Choose a product and number of bags per batch, or enter the finished volume your mixer actually yields; the calculator does not infer usable output from a drum’s advertised capacity.
Choose how you know a batch yield
Start with the concrete volume the project needs, including any material allowance you intend to order. The default path can use a selected bagged concrete product and the number of bags mixed together per batch. A second path accepts the actual finished concrete volume produced by one batch. Use an amount from your equipment instructions or a measured trial, not the mixer drum’s total geometric capacity.
The bag path needs a product because bag weight alone does not determine yield. For example, the QUIKRETE Concrete Mix No. 1101 data sheet gives approximate yield of 0.60 ft³ for an 80 lb bag and 0.45 ft³ for a 60 lb bag. Two 80 lb bags therefore represent about 1.20 ft³ of product yield before practical mixing conditions. The actual load size must remain within the mixer manufacturer’s operating instructions.
How the calculator turns volume into batches
The tool first determines how many whole bags are needed for the total order quantity, rounding the purchase count upward. It then divides that whole-bag count by the selected bags per batch and rounds the number of batches upward: batches = ceil(total bags ÷ bags per batch). This keeps the result actionable; a displayed 20.67 batches would not tell you how many separate loads to prepare.
If you enter a known finished batch yield instead, the calculator divides the required adjusted volume by that yield and rounds upward. Those paths answer related questions but use different evidence: product yield plus bag count, or measured output from your equipment and process. Do not combine the two yields or use the nominal drum volume as though it were fully available concrete. If the final batch is smaller, the tool can show its remaining bag count or volume.
Worked example: a slab requiring 62 bags
A 10 ft × 10 ft slab at 4 in thickness has about 1.23457 yd³ net volume. With a 10% allowance, the planned order is about 1.35802 yd³. At the named 80 lb mix yield of approximately 0.60 ft³ per bag, that quantity requires 62 bags after rounding up. If the mixer is loaded with two bags per batch, 62 ÷ 2 equals 31 full batches.
Suppose you enter a complete 10-minute cycle for each batch. The sequential cycle estimate is 31 × 10 = 310 minutes. If your permitted load were instead three bags at a time, the calculator would show 21 batches, with 20 full three-bag batches and a final two-bag batch. The 310 minutes is not a promise for total project duration: it excludes setup, moving material, placing, finishing, cleaning, interruptions, and any time required to keep a pour continuous.
Use a realistic cycle time
The optional time input should describe a full repeatable cycle using the same definition for every batch. Depending on how you measure it, that might include loading, mixing, discharge, and resetting the mixer. Enter minutes for one complete cycle; the displayed sequential estimate multiplies that value by the number of batches. If the last batch is smaller, this simple multiplication may overstate its time, so treat the result as a planning estimate unless you measure that smaller cycle separately.
Time estimates do not account for how many people are working or whether one person can prepare the next load while another places concrete. They also do not decide the maximum safe or workable mixer load. Read the mixer manual, consider the mix instructions, and make a placement plan before starting. A batch count is useful for staging bags, water, tools, and helpers, but it is not an equipment safety assessment or a structural placement plan.
Mixer batches are different from delivery loads
An on-site mixer batch is a single amount mixed in the equipment. A ready-mix delivery load is a supplier’s truck and dispatch arrangement. This calculator estimates the former. If you want truck-load count, use a known usable truck capacity and ask the supplier about its fleet, minimum order, partial-load terms, and access. A mixer’s drum size does not tell you the truck capacity, and an order quantity does not establish how fast a site can place the material.
Bagged mixing can be practical for a small pour or a location that is difficult for delivery, but many repeated batches add handling and coordination. Compare the bag count and estimated work sequence with a local ready-mix quote before deciding. The material amount is not a cost comparison by itself. If you do proceed with on-site mixing, keep a consistent recipe and water measurement, and do not change the mix in order to match a time target.
Errors and limits
The tool needs a positive required volume and a positive batch yield or positive integer bag count per batch. Blank fields are not treated as zero. A yield of zero, a negative value, or a non-finite number cannot produce a meaningful batch count. Correcting an input should preserve the other measurements. If the requirement is very small, the final load may be only part of a normal batch; the page should show the leftover amount rather than claiming the entire batch must be discarded.
This is a quantity and sequencing aid. It does not set concrete strength, water content, aggregate grading, mixer capacity, safe lifting limits, placement rate, or local design requirements. For the bag yield, verify the exact product and package. For the mix itself, follow the selected product directions or a qualified project specification. If calculating a custom site recipe, use the mix-ratio calculator’s named purchasing or volume-ratio mode; those methods should not be confused with batching bagged premix.
Frequently asked questions
Does the drum capacity equal one batch of concrete?
No. Drum capacity is not necessarily usable finished output. Enter the actual batch yield or derive it from a selected bag yield and a load allowed by the mixer instructions.
How many batches are needed for 62 bags at two bags per batch?
The calculator rounds 62 ÷ 2 up to 31 batches. If the division is not even, it can show the smaller final batch separately.
Can I enter a mixer model?
Use a model preset only when a verified source documents its actual usable output. Otherwise enter a measured finished yield for your mixer and process.
Does the time estimate include finishing the slab?
No. It multiplies the entered full cycle time by batch count. Setup, material handling, placement, finishing, cleaning, and delays are separate.
Can this estimate ready-mix truck trips?
No. It estimates on-site mixer batches. Use the volume and a supplier-confirmed usable delivery capacity for a separate truck estimate.
What bag yield should I use?
Select the exact product and package size. QUIKRETE Concrete Mix No. 1101 lists approximate yields by bag size; other mixes may differ.