Concrete Mixer Capacity Calculator
Plan your pour before you start the mixer. This free concrete mixer capacity calculator turns the amount of concrete you need into a batch plan: how many mixer loads, how many bags go in each load, the total bags to buy, and how long batching will take. It's made for site-mix and bag-mix jobs — if you need to estimate the volume itself first, use our concrete slab calculator, then bring the number back here.
Enter your numbers
Your results
| Total concrete | – |
|---|---|
| Mixer batch capacity | – |
| Bags per load | – |
Bag yields are typical values: an 80-lb bag ≈ 0.6 cu ft, a 60-lb bag ≈ 0.45 cu ft. Actual yield varies by brand and mix — check the bag. Time is an estimate; pour speed, hauling distance, and crew size all affect it.
How to use this calculator
Enter how much concrete your job needs, either in cubic yards or cubic feet — one cubic yard is 27 cubic feet, so you can type the number your supplier or a volume estimator gave you without converting it yourself. If you're still figuring out the volume, estimate it with our concrete slab calculator first, then come back here with the number.
Pick your mixer size: 3.5 cu ft for small portable drums, 6 cu ft for mid-size mixers, or 9 cu ft for large portable mixers, or enter your own drum's rated batch capacity. Choose the bag size you're buying (80-lb or 60-lb bags), and set the minutes each full cycle takes you — a 20-minute default covers loading, mixing, pouring, and a quick rinse of the drum.
You'll get a batch plan: the number of loads to mix, how many whole bags go in each load, the total bags to buy, and the estimated active batching time. Print it, take it to the job site, and stack your bags by load — knowing the bags-per-load number keeps you from overfilling the drum.
How it works
First the tool converts your concrete amount to cubic feet: cubic yards × 27, or the cubic-foot value you entered directly. Then it divides by your mixer's batch capacity and rounds up — because a half-load still costs you a full cycle. That's the load count: loads = ceil(total cu ft ÷ mixer capacity).
Bags per load come from the bag's cured yield: bags per load = floor(mixer capacity ÷ bag yield), with 0.6 cu ft for an 80-lb bag and 0.45 cu ft for a 60-lb bag as typical values. We round down here so you never overfill the drum. Total bags to buy round up instead: total bags = ceil(total cu ft ÷ bag yield), so you don't come up short.
Batching time is simply loads × minutes per load, shown as hours and minutes. A quick note on water: aim for a water–cement ratio around 0.45–0.60 by weight and follow the bag's water guidance — add water gradually and never exceed the bag's maximum, since extra water weakens the finished concrete. These are planning estimates, not engineering specifications.
Frequently asked questions
How many mixer loads will my job take?
Divide your total concrete by your mixer's capacity and round up: loads = ceil(total cubic feet ÷ mixer capacity in cubic feet). For example, 2 cubic yards (54 cu ft) in a 9 cu ft mixer is exactly 6 loads. Rounding up matters because a partial load still costs you a full cycle of loading, mixing, pouring, and cleaning.
How many bags of concrete mix fit in one mixer load?
It depends on the bag size. A typical 80-lb bag yields about 0.6 cubic feet of concrete, and a 60-lb bag yields about 0.45 cubic feet. Bags per load = floor(mixer capacity ÷ bag yield). A 9 cu ft mixer holds 15 bags of 80-lb mix (9 ÷ 0.6 = 15) or 20 bags of 60-lb mix (9 ÷ 0.45 = 20). Always round down per load so you don't overfill the drum.
Should I fill my concrete mixer to full capacity?
No — keep each batch at or below the mixer's rated batch capacity, not the drum's total volume. Overfilling makes the mix turn over poorly, mixes longer, and can spill or strain the motor. The capacities in this calculator's presets (3.5, 6, and 9 cu ft) are typical batch capacities for small, medium, and large portable mixers.
How long does it take to batch and pour concrete by mixer?
A common rule of thumb is about 20 minutes per load covering loading, mixing, pouring, and a quick rinse. Total time = loads × minutes per load. For 6 loads at 20 minutes each that's 2 hours of active batching time. Increase the cycle time if you have long hauls, a slow pour, or only one person working.