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Buying Concrete: Bags or Ready-Mix, What to Order and How to Plan the Pour

Published October 14, 2026Last reviewed October 202620 sources

Bags or ready-mix?

Concrete is bought two ways: as dry mix in bags you mix yourself, or as ready-mix delivered by truck and placed straight from the chute. The calculator tells you how much you need. This guide covers how to buy it, what to tell the supplier, and how to get ready for the day the concrete arrives.

Should I use bagged concrete or ready-mix?

It comes down to quantity and effort. Ready-mix is sold by volume, in cubic yards, and truck mixers carry 8 to 12 cubic yards1. Bagged mix is sold by weight, and the bag tells you its yield: about 0.30 cubic feet for a 40 lb bag, 0.45 for 60 lb and 0.60 for 80 lb23. One cubic yard is 27 cubic feet20, so it takes roughly 90, 60 or 45 bags.

Bags suit posts, small pads, steps and repairs. Every bag has to be carried, mixed and placed while the earlier batches are still workable, and the weight adds up quickly: 100 bags of 80 lb is only about 2.22 cubic yards but 8,000 lb to lift. For comparison, a small 8-yard truckload would be about 360 bags. Past about 100 bags, CalcBrite points you to ready-mix suppliers first; that’s our judgment about effort, not an industry rule.

Ready-mix arrives mixed and goes in as one pour, but it comes with conditions: the crew must be ready when the truck arrives1, and suppliers may charge for short loads7.

How do I mix bagged concrete?

Follow the bag. For QUIKRETE Concrete Mix, start with about 6 pints of water per 80 lb bag and add water only until the mix is stiff and moldable, about 6 to 9 pints in total; a mixer needs at least 1 cubic foot of drum capacity per 80 lb bag2. Mixing by hand in a wheelbarrow or mortar box works for small amounts; make sure there are no dry pockets. Standard bagged concrete is meant for sections at least 2 inches thick23.

Not sure how much you need? Enter your slab, footing or post holes and compare the bag count with a ready-mix order.
Concrete Calculator

What to order

What should I tell a ready-mix supplier?

A ready-mix order is more than a volume. NRMCA’s guide to ordering lists the coarse aggregate size, slump, air content, strength or mix requirements, quantity, any extras such as fibers or color, the delivery schedule and truck access1. For a typical residential slab, these are the usual starting points; your plans or local code take priority.

What to specify when ordering ready-mix concrete
ItemCommon starting pointSource
Strength (psi)3500 to 5000 psi is typical; 4000 psi for exterior slabs exposed to moisture or deicers, 3500 psi where they aren’t14
Air contentAir-entrained where the concrete will freeze; about 6% with ¾ or 1 in aggregate14
Slump3 to 5 inches for most work; no more than 5 inches for slabs15
Aggregate size¾ or 1 inch for most work, and smaller than the thinnest section1
QuantityCubic yards, plus 4 to 10% for contingencies16

Does outdoor concrete need air entrainment?

Where it freezes, yes. Air-entrained concrete is required for concrete exposed to freezing temperatures in service, and the purchaser should state the air content or the exposure1. For exterior slabs with ¾ or 1 inch aggregate, NRMCA recommends about 6 percent total air4. Saying “exterior patio, freezes in winter, deicers possible” gives the supplier what they need.

How much extra concrete should I order?

NRMCA suggests ordering 4 to 10 percent more than the volume from plan dimensions, to cover waste, over-excavation and other contingencies16. Small errors add up: a ⅛-inch difference in a 4-inch slab is a 3 percent shortage6, and a second small load to finish a pour is the thing to avoid6. The calculator shows the exact volume and lets you add the allowance you choose.

What to confirm with your supplier

What should I ask before booking?

  • The minimum order and any short-load or returned-concrete charges7.
  • The delivery date and start time, and how fast you can place it if more than one truck is coming17.
  • The time limit to unload. The current ASTM C94 standard leaves it to the purchaser or, failing that, the producer, who prints it on the delivery ticket; earlier editions used 1½ hours from mixing8.
  • How long you get on site before waiting charges start; that is set by each supplier10.
  • Where the driver can wash out the chute710.
  • How the concrete reaches the forms: straight from the chute, by wheelbarrow, or with a pump or conveyor17.

Where can the truck go?

A loaded concrete truck weighs about 80,000 lb and may not manage loose dirt, residential curbs or pathways1. Plan the route before the order. Producers warn about overhead wires and branches, and ask customers to keep the truck off existing driveways, sidewalks, patios, sprinkler systems and septic tanks, mark buried obstacles and have a spotter for backing10. If the truck can’t get close enough, ask about a pump.

Can I add water to ready-mix on site?

Only within the mix design, and only before any concrete has been discharged. Water beyond the design amount delays setting, reduces strength and durability and increases the risk of cracking; if the purchaser asks for more, the purchaser takes responsibility for the quality, and all water added is recorded on the delivery ticket9. If the concrete seems too stiff, ask the driver what the mix allows rather than reaching for a hose.

Preparing the site

What has to be ready before the concrete arrives?

Everything. NRMCA’s finishing guide says to complete subgrade excavation and compaction, formwork and any mesh, reinforcement or embedded items before delivery11. Remove topsoil and soft spots, compact the soil or granular fill evenly, slope it for drainage, and never place concrete on frozen ground511. On dry days, lightly dampen the subgrade and forms just before the pour, without leaving standing water512.

4 inConcrete to the top of the formsCompacted gravel base, dampFirm, evenly compacted subgradeForms and stakes
A slab ready to pour: firm compacted subgrade, a compacted gravel base, forms staked with their tops at the finished height, and a damp (not wet) surface just before the concrete goes in.

How thick should a patio or walkway be?

Use the thickness on your plans or required locally. As a common reference, QUIKRETE’s project instructions call for sidewalks at least 4 inches thick and small slabs normally 4 to 6 inches, depending on the load they carry13.

Do I need a permit for footings or post holes?

Often, and the rules vary by place. Two Minnesota cities show how much: New Ulm requires a permit for a deck, footings at least 42 inches below grade and an inspection after the holes are dug and before concrete is poured14; Duluth puts frost-depth footings at 60 inches and also inspects before the pour15. New Ulm also reminds residents to call the state’s one-call service 48 hours before digging14. Check with your local building department before you dig, and book the inspection before you book the concrete.

Use the footing and post-hole modes for the exact sizes your plans or inspector require.
Concrete Calculator

Pour day

What should I have ready on the day?

Concrete is perishable: the crew should be ready when the truck arrives1. Have enough people to place, level and finish, the tools laid out, and protective gear for everyone. Fresh concrete causes chemical burns: keep it off skin, wear rubber boots, gloves and eye protection, don’t let it soak into clothing, and wash skin promptly with clean water12. Keep children away from fresh concrete1.

How do I finish a slab without ruining the surface?

Place and level the concrete, then bull float it before bleed water appears. Then wait: any finishing done while the concrete is still bleeding or has water on the surface causes dusting, scaling, crazing and blisters. Never sprinkle water or cement on the surface to make finishing easier, and don’t use a garden rake to move concrete sideways. On outdoor slabs, broom the surface after floating for a non-slip finish11.

Can I pour in hot or cold weather?

Heat and wind speed everything up. In hot weather NRMCA advises avoiding the hottest part of the day, dampening the subgrade and forms, having trucks discharge without waiting, starting final finishing as soon as the water sheen has gone and starting curing right after16.

Cold is the bigger risk. Fresh concrete freezes below about 25°F, and frozen concrete can lose more than half its potential strength; protect it until it reaches about 500 psi, roughly two days17. Clear snow and ice, don’t pour on frozen ground, and cover the slab with insulated blankets, tarps, or straw under plastic, paying attention to edges and corners17. For bagged mix, QUIKRETE says to protect it from freezing for the first 48 hours2.

Joints and curing

How far apart should control joints be?

Concrete shrinks as it dries, and joints decide where it cracks. NRMCA puts the maximum spacing at 24 to 36 times the slab thickness, about 10 feet for a 4-inch slab and never more than 15 feet, keeps panels square or nearly so (no more than 1.5 times longer than wide, no L-shapes), and cuts the groove at least a quarter of the slab’s thickness and not less than an inch; saw-cut joints go in within 4 to 12 hours of finishing18. Product instructions for small bagged-mix slabs can be closer: QUIKRETE’s call for joints every 6 to 8 feet2.

12 ft10 ft6 × 5 ft4 in slabjoints ≤ 10 ft apartpanels near squarecut ¼ deep (1 in)
A 12 × 10 ft slab, 4 in thick, laid out with joints no more than 10 ft apart and near-square panels: 4 panels of about 6 × 5 ft. Panel sizes are calculated from the NRMCA rule of thumb.

How long should new concrete cure?

Curing starts as soon as finishing is done and typically continues for 3 to 7 days, with the concrete kept above 50°F; concrete left to dry out can lose as much as half its potential strength compared with concrete kept moist19. QUIKRETE gives 5 days in warm weather (70°F or more) and 7 days at 50 to 70°F for its mix2.

  • Plastic sheeting at least 4 mils thick, laid on the surface as soon as possible, edges overlapped and weighted; it can mark the surface, so skip it where appearance matters19.
  • Wet burlap or continuous sprinkling, kept wet; alternate wetting and drying is not curing19.
  • A curing compound sprayed once the water sheen has gone, ideally in two coats at right angles19.

Before you order: your concrete checklist

  • Measure every pour and run it through the calculator; add the allowance you choose.
  • Decide bags or ready-mix by the bag count, the weight you’d handle and the help you have.
  • Check your plans or local code for thickness, strength and footing depth, and whether you need a permit or inspection.
  • For ready-mix: give the supplier the strength, slump, air content and aggregate size, and say it’s exterior if it is.
  • Ask about minimum orders, short-load charges, the time allowed to unload and waiting charges.
  • Confirm where the truck will park and how concrete gets from the chute to the forms.
  • Have the subgrade compacted, forms set, reinforcement placed and inspections done before the truck is booked.
  • Check the forecast; plan protection for heat, wind or freezing nights.
  • Line up enough helpers, tools, gloves, boots and eye protection.
  • Have curing covers or compound ready before you start finishing.
Ready to order? Get the cubic yards, bag count and a ready-mix quantity for every pour in one place.
Concrete Calculator

Sources

  1. CIP 31: Ordering Ready Mixed Concrete, National Ready Mixed Concrete Association, Concrete in Practice (2000, 2016, 2023) — concrete is sold by volume in cubic yards (cubic meters); order 4% to 10% more than the volume from plan dimensions.
  2. QUIKRETE Concrete Mix No. 1101, product data sheet, The Quikrete Companies; revised October 2022 — “A 40 lb (18.1 kg) bag yields approximately 0.30 ft3 … A 60 lb (27.2 kg) bag yields approximately 0.45 ft3 … An 80 lb (36.2 kg) bag yields approximately 0.60 ft3” (industry source).
  3. SAKRETE High-Strength Concrete Mix, SAKRETE of North America (product page and technical data sheet) — “Yields 0.30 ft3 (40 lb bag); 0.45 ft3 (60 lb bag); 0.6 ft3 (80 lb bag)” (industry source).
  4. CIP 2: Scaling Concrete Surfaces, National Ready Mixed Concrete Association, Concrete in Practice (1978–2014) — exterior slabs: 4000 psi, consistent with ACI 332, or 3500 psi where the concrete won’t stay moist and no deicers are used; air-entrained, about 6 percent with ¾ or 1 in aggregate.
  5. CIP 4: Cracking Concrete Surfaces, National Ready Mixed Concrete Association, Concrete in Practice (1978–2014) — remove topsoil and soft spots, compact the subgrade, never place on frozen ground; slump not over 5 in; air-entrained concrete outdoors where it freezes; keep moist at least 3 days.
  6. CIP 8: Discrepancies in Yield, National Ready Mixed Concrete Association, Concrete in Practice (1979–2016) — “Include an allowance of 4 to 10 percent over plan dimensions for waste, over-excavation and other contingencies”; avoid short loads.
  7. Checklist for Ordering and Scheduling Ready Mixed Concrete, National Ready Mixed Concrete Association and American Society of Concrete Contractors — items to agree with the supplier include “additional charges for items like returned concrete, short loads”.
  8. PIN 82: Ready Mix Concrete/Grout Placement Times, California Department of Health Care Access and Information; effective October 9, 2025 — ASTM C94/C94M-24d no longer sets a fixed time from mixing to placement; the purchaser states a limit, or the producer sets one and prints it on the delivery ticket; earlier editions used 1½ hours.
  9. CIP 26: Jobsite Addition of Water, National Ready Mixed Concrete Association, Concrete in Practice (1995–2023) — water beyond the design amount delays setting, reduces strength and durability and increases cracking; no water once concrete has been discharged; any water added is recorded on the ticket.
  10. Preparing for your concrete pour, Cranesville Block Co. (ready-mix producer, New York) — one producer’s customer instructions: overhead clearance, keep the truck off driveways, septic and sprinklers, mark obstacles, have a spotter and a washout spot; its unloading allowance and overtime charges are its own terms (industry source).
  11. CIP 14: Finishing Concrete Flatwork, National Ready Mixed Concrete Association, Concrete in Practice (1986–2017) — finish subgrade, forms and reinforcement before delivery; bull float before bleed water appears; wait until bleeding stops and the sheen is gone; never sprinkle water or cement; broom exterior slabs; wear protective clothing.
  12. CIP 5: Plastic Shrinkage Cracking, National Ready Mixed Concrete Association, Concrete in Practice (2014) — dampen the subgrade, but not to the point of free-standing water.
  13. Concrete Sidewalks and Small Slabs, The Quikrete Companies (project instructions) — sidewalks at least 4 in thick; small slabs for bases normally 4 to 6 in, depending on the load (industry source).
  14. Residential Deck Information, City of New Ulm, Minnesota — permit required; footing bottoms at least 42 in below grade; footing inspection before pouring; call the state one-call service 48 hours before digging.
  15. Residential Decks, City of Duluth, Minnesota, Construction Services & Inspections — frost-depth footings are 60 in below grade; footings inspected before concrete is poured.
  16. CIP 12: Hot Weather Concreting, National Ready Mixed Concrete Association, Concrete in Practice (1982–2014) — avoid the hottest part of the day; dampen subgrade and forms without ponding; trucks should discharge immediately; start finishing when the sheen has gone and cure at least 3 days.
  17. CIP 27: Cold Weather Concreting, National Ready Mixed Concrete Association, Concrete in Practice (1998, 2014) — fresh concrete freezes below about 25°F and can lose more than half its potential strength; protect it until about 500 psi, about two days; no snow, ice or frozen surfaces; blankets, tarps or straw under plastic.
  18. CIP 6: Joints in Concrete Slabs on Grade, National Ready Mixed Concrete Association, Concrete in Practice (1979–2014) — maximum joint spacing 24 to 36 times the slab thickness, about 10 ft for a 4 in slab, never over 15 ft; near-square panels; groove at least ¼ of the thickness and not less than 1 in; saw-cut within 4 to 12 hours.
  19. CIP 11: Curing In-Place Concrete, National Ready Mixed Concrete Association, Concrete in Practice (1982–2017) — start curing right after finishing and continue typically 3 to 7 days; keep concrete above 50°F; plastic at least 4 mils, wet burlap, sprinkling or curing compound; never alternate wetting and drying.
  20. Guide to the SI, Appendix B.8: cubic yard, cubic foot and short ton factors, NIST Special Publication 811.
Last reviewed:
October 2026
Published:
October 14, 2026
Last updated:
October 14, 2026
Guide version:
1.0

Ordering, finishing, weather, joint and curing guidance comes from the National Ready Mixed Concrete Association’s Concrete in Practice sheets; bag yields, mixing and small-slab instructions from QUIKRETE and SAKRETE product literature; truck access tips from one ready-mix producer’s customer instructions, whose fees and terms are its own. Permit and footing examples are from two Minnesota cities and show how rules vary; your local building department decides. The 100-bag point is CalcBrite’s judgment, not a published threshold. CalcBrite doesn’t recommend a supplier.

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