Bagged Concrete vs Ready-Mix: Which Should You Use?
Both bagged premix and ready-mix concrete make good concrete. The choice is about volume, labor, timing and access. Here is how to decide, with the numbers behind the usual rule of thumb.
What you are actually buying
Bagged concrete is a dry blend of cement, sand and aggregate. You add water and mix it in a wheelbarrow, a tub or a small drum mixer. Each bag yields a fixed volume — around 0.6 cu ft for an 80 lb bag or 9–14 L for a 20–30 kg bag — printed on the label.
Ready-mix is batched at a plant to a specified strength and delivered in a drum truck, ready to place. You order it by volume (cubic yards or cubic meters), and the plant controls the water-cement ratio and consistency. Mini-mix or volumetric trucks, which mix on site, are common in the UK for smaller orders.
The volume threshold
The usual rule of thumb is that bags make sense up to about one cubic yard (0.76 m³). Here is why: one cubic yard is roughly 45 bags of 80 lb premix — 3,600 lb of material to lift and mix, and about 45 mixer loads. Two people with a mixer can manage that in an afternoon, but the first batches will be stiffening before the last are placed, which makes finishing a large slab difficult.
| Volume | 80 lb bags (0.6 cu ft) | 25 kg bags (~11.7 L) |
|---|---|---|
| 0.25 cu yd / 0.19 m³ | 12 | 17 |
| 0.5 cu yd / 0.38 m³ | 23 | 33 |
| 1 cu yd / 0.76 m³ | 45 | 66 |
| 2 cu yd / 1.53 m³ | 90 | 131 |
Cost comparison
Per cubic yard, bagged concrete is usually more expensive than ready-mix, but ready-mix has fixed costs: delivery, and often a short-load fee for orders below a minimum. For a very small job those fees dominate and bags win. Somewhere between about one and three cubic yards the lines cross, depending on local prices. The only way to know is to price both: take the bag count from our bag calculator, multiply by the shelf price, and compare with a delivered quote that includes all fees.
Remember to include equipment: mixer hire, a wheelbarrow, and possibly a concrete pump if the truck cannot reach the pour. A pump adds cost but can save hours of barrowing.
Quality and finish
- Ready-mix arrives uniform, so a large slab finishes evenly with no visible batch lines.
- Bagged mixes vary with how much water each batch gets; too much water weakens concrete.
- Fast-setting bagged mixes are excellent for posts and small repairs but give little working time.
- For any pour you cannot finish in one go, plan a proper construction joint.
Questions to ask a ready-mix supplier
- What is the minimum order, and what is the short-load fee below it?
- What increments do you deliver in (¼ yd, 0.2 m³)?
- How much time is included for unloading before waiting charges start?
- Can the truck reach my forms, and what is the maximum chute reach?
- What mix do you recommend for a patio, driveway or footing in my area?
Mixing bags well
If you choose bags, consistency is everything. Use the same amount of water in every batch — measure it rather than pouring from a hose — and mix for the time the manufacturer recommends, typically a few minutes in a drum mixer. Too much water makes concrete easier to place but weaker and more prone to cracking and dusting. Work in a steady rhythm so each batch is placed against concrete that is still workable.
Have a plan for the labor. A 60 lb or 25 kg bag is manageable for most people, but lifting 50 or more in a session is hard work. Stage pallets close to the mixer, keep the mixer close to the pour, and have at least one person placing and finishing while another mixes.
Other options between the two
- Mini-mix or volumetric trucks mix on site and charge for what you use — useful for 1–3 m³ jobs and common in the UK.
- Trailer-mounted mixers hired from some yards can carry around half a cubic yard of ready-mix.
- Concrete pumps or "line pumps" move ready-mix through a hose when the truck cannot reach.
- Fast-setting post mixes are poured dry into post holes and water added — ideal for fences, not for slabs.
A simple decision rule
Use bags for post holes, small pads, steps and repairs. Get a ready-mix quote for anything over about a cubic yard, or any slab you want to finish in one smooth pour. When in doubt, calculate both with our tools and let the numbers — and your back — decide.
Calculators for this guide
- Concrete Bag Calculator — How many bags of concrete do you need? Compare 40, 60 and 80 lb or 20, 25 and 30 kg bags, total weight and cost — with the math shown.
- Concrete Slab Calculator — Estimate cubic yards, cubic meters and bags of concrete for a slab, patio or pad — with waste factor, the formula and a shopping list.
More guides
Estimates only. This guide explains general methods. Verify quantities with your supplier and follow local building codes; for structural or safety-critical work consult a licensed professional. Editorial policy · Report an error.