Concrete Calculator for Deck Footings: Tubes, Piers & Bags

A concrete calculator for deck footings should first identify the footing type, then calculate the concrete quantity. Most deck searches are really asking one of four different jobs: round form tubes, post holes with a post inside the hole, a continuous rectangular footing under a beam, or a larger drilled pier or caisson.

Use the Concrete Form Tube Calculator for round Sonotube-style deck footings. Use the Concrete Post Hole Calculator when a post occupies part of the hole and concrete fills the ring around it. Use the Concrete Footing Calculator for a continuous rectangular footing, grade beam, or wall footing. Use the Pier & Caisson Concrete Calculator for large drilled shafts, bells, or pier groups that need separate geometry.

Quick answer

For ten round deck footing tubes at 12 inches diameter and 36 inches deep, plan about 0.96 cubic yards with 10% waste, or about 44 common 80 lb bags. That is a material quantity check only. It does not approve the deck design, frost depth, bearing area, reinforcement, inspection, post-base hardware, or contractor scope.

The fastest safe workflow is: confirm the approved footing detail, calculate volume, add waste, compare 60 lb or 80 lb bags against ready-mix minimums, then review the contractor quote line by line.

Pick the calculator by footing shape

Do not force every deck footing into one formula. The right calculator depends on the concrete shape that will actually be filled.

This split is the main advantage over a generic concrete calculator. A deck builder, DIY homeowner, or estimator can keep the material math separate from structural approval and bid scope.

Round deck footing formula

For a round tube or pier:

cubic feet = 3.1416 x radius ft x radius ft x filled depth ft
cubic yards = cubic feet / 27
total order quantity = cubic yards x number of footings x waste factor

A 12 inch diameter tube has a 0.5 ft radius. At 36 inches deep, one tube is:

3.1416 x 0.5 x 0.5 x 3 ft = 2.36 ft3
2.36 ft3 / 27 = 0.087 yd3 before waste
0.087 yd3 x 10 tubes x 1.10 = 0.96 yd3 with waste

For 80 lb bags with a common 0.60 ft3 yield:

2.36 ft3 x 10 x 1.10 / 0.60 = 43.2 bags
round up to 44 bags

If your bag's printed yield is different, use the label. Manufacturer tools such as the QUIKRETE concrete calculator and Sakrete concrete calculators show why bag yield, rounding, and waste matter on small jobs.

60 lb vs 80 lb bags for deck footings

The same footing volume can produce very different bag counts depending on bag size. The calculation below uses common planning yields, not a warranty for any specific product.

For pickup planning, a pallet question is often more important than the volume question. A common 80 lb pallet is about 42 bags, and a common 60 lb pallet is about 56 bags, but the exact count depends on the store and product. Check the How Many Bags of Concrete on a Pallet guide before you send a truck.

When ready-mix becomes worth checking

Deck footings often fall near the awkward middle: too many bags to mix easily, but not enough cubic yards to avoid a minimum-load or short-load charge. The calculator should not decide for you; it should show both paths clearly.

Use the Ready-Mix vs Bags Calculator once the bag count climbs. Ask the supplier about minimum billable yards, short-load fees, delivery windows, wait time, truck access, chute reach, and washout. NRMCA ordering guidance is useful here because concrete dispatch timing and clear instructions can matter as much as the raw yardage.

What the calculator cannot approve

A deck footing quantity calculator is not a deck engineering tool. It should not choose footing diameter, depth, soil bearing capacity, frost depth, rebar, connector hardware, beam spans, joist spans, or ledger details. Those decisions belong to approved plans, local code, the building department, an engineer, or a qualified deck professional.

Use the calculator after those inputs are known. If the inputs are not known, write the unknowns into the quote request instead of guessing. A clean request sounds like this:

Please price ___ deck footings at ___ inch diameter and ___ inch depth, based
on the approved plan. Include layout, digging, tubes/forms, reinforcement if
required, post-base hardware responsibility, inspection timing, concrete,
placement method, cleanup, and exclusions.

If a bidder cannot state the diameter, depth, count, concrete method, and exclusions, the installed price is not ready to compare.

Quote checklist for deck footing concrete

Use this checklist after the calculator gives a material number.

For contractor comparison, use the Deck Footing Contractor Quote Checklist and then normalize the final numbers in the Concrete Quote Reviewer.

Common mistakes that change the bag count

The bag count changes quickly when the field condition is not the same as the plan. Watch for these before buying concrete:

• Over-dug holes. A 12 inch tube placed in a much wider hole may need extra backfill or extra concrete depending on the detail.
• Different filled depth. A 36 inch hole and a 48 inch hole are not close on material quantity across ten or more footings.
• Bell bottoms. A belled footing should be calculated separately from the straight shaft.
• Post displacement. If the post is inside the hole, subtract the post volume or use a post-hole calculator.
• Waste hidden twice. Do not add 10% in the calculator and then again in a supplier worksheet unless you mean to buy that much cushion.
• Bag yield mismatch. Use the product label for yield. Do not assume every 60 lb or 80 lb bag yields the same amount.
• Pallet and payload limits. Concrete dry mix is heavy. Confirm store pallet counts, trailer capacity, pickup payload, and unloading method.

Sources and assumptions

The deck-footing material examples on this page use cylinder and rectangular prism volume formulas, a 10% planning waste factor, common 80 lb bag yield of about 0.60 ft3, and common 60 lb bag yield of about 0.45 ft3. Verify the printed bag yield and the approved deck-footing detail before ordering.

Helpful references for estimator checks include the Decks.com concrete calculator for deck footings, QUIKRETE concrete calculator, Sakrete concrete calculators, Sonotube Builders Tube, and NRMCA ordering resources for ready-mix dispatch planning.