How much concrete for 8 footings 18x18x10?

Data checked October 2026

Short answer

8 pads of 18×18×10 in take 0.56 cubic yards of concrete — 28 × 80-lb bags with 10% extra, or 1 yd³ of ready-mix.

Each pad: 18 × 18 × 10 in = 1.88 cu ft (3.13 × 80-lb bags); × 8 = 15 cu ft.
Bags with 10% extra: 28 × 80 lb or 37 × 60 lb — 2,240 lb to move.
Cost: about $181 in bags vs. $485 for 1 yd³ delivered — bags are the obvious choice.
18 in pads spread a post load over more soil — the direction IRC Table R507.3.1 pushes larger decks and weaker soils.

Adjust it to your exact job

Footing type

What are you pouring?

Pads

Number of pads

Common pad sizes (L × W × thick, in)

Length

= 1' 6"

Width

= 1' 6"

Thick

= 10"

You need

28× 80-lb bags

0.61 yd³ of concrete for 8 × 18×18×10 in pads, including 10% extra · 2,240 lb of bags

Concrete volume: 0.56yd³15 ft³ before waste
Per pad: 1.88ft³3.13 × 80-lb bags
Ready-mix order: 1yd³quarter-yard steps, 1 yd minimum
Finished weight: 1.1tons

Code check (IRC 2021)

Thickness 10 in — meets the ruleR403.1.1: footings at least 6 in thick. Deck footing size comes from Table R507.3.1 (load and soil).

Other bag sizes

Bags needed by size
Bag	Bags	Est. cost
40 lb · 0.3 ft³	55	—
50 lb · 0.375 ft³	44	—
60 lb · 0.45 ft³	37	$179
80 lb · 0.6 ft³	28	$181

Bags or a ready-mix truck?

28 bags

$181

Cheaper ✓ · materials only, before tax

1 yd³ delivered

$485

incl. short-load & delivery fees

At these prices a truck becomes cheaper from about 3.25 yd³ (147 bags). Over 1–2 yd³, a truck also saves hours of mixing: plan on 3–4 minutes per bag in a mixer.

That's 1.1 tons of bags — more than most pickups can carry in one trip. Ask about store delivery.

How deep?

The bottom of every exterior footing must sit at least 12 in below undisturbed ground (IRC R403.1.4) and below your local frost depth, which the building department sets. Dig to firm, undisturbed soil — never pour on loose fill.

Timeline for standard 4000 psi mix

Walk on: 24 hours
Light loads / posts: 24 hours
Keep moist (cure): 5 days ≥70°F · 7 days at 50–70°F
Protect from freezing: 48 hours

Shopping list

28 bags Standard 4000 psi mix — 80-lb bags$181
32 gal Clean water for mixing21–32 gal; start low, never exceed the max

Estimated total$181

Cost estimate

Tap a price to use your store's

80-lb Standard 4000 psi mix
28 bags × $
$181

Materials total$181

Typical U.S. prices checked October 2026. Tap any price to enter your store's.

Did this answer your question?

Compare

8 pads at other sizes

Size	Cubic yards	80-lb bags	60-lb bags	Bag cost	Ready-mix
12×12×12 in	0.3	15	20	$97.05	$485
18×18×10 in	0.56	28	37	$181	$485
24×24×12 in	1.19	59	79	$350	$570
30×30×12 in	1.85	92	123	$546	$698

How this was worked out

18 × 18 × 10 = 3,240 cu in per pad, ÷ 1,728 = 1.875 cu ft. Times 8 pads = 15 cu ft, ÷ 27 = 0.556 yd³.

With 10% extra that is 16.5 cu ft ÷ 0.6 cu ft per 80-lb bag = 27.5, rounded up to 28 bags.

At 0.61 yd³ with waste this is a bag job — a truck's 1 yd minimum plus fees would cost about $485.

The full method, material data and tips are on the main concrete footing calculator page.

Similar jobs

Other sizes people check

Sources

Data behind this answer

Quikrete Concrete Mix No. 1101 — technical data sheet — bag yields (80 lb = 0.60 cu ft, 60 lb = 0.45, 50 lb = 0.375, 40 lb = 0.30), water per bag, curing times; post method: 6 in of dry mix in the hole bottom, 24 h before strain · checked October 2026
Sakrete High-Strength Concrete Mix — TDS — same yields per bag weight; Sakrete recommends +10% overage · checked October 2026
Home Depot & Lowe's listings — Quikrete 80 lb Concrete Mix — $5.98–$6.98 per 80-lb bag; $5.93 bulk tier at 42+ bags; 42 bags per pallet; Fast-Setting 50 lb $7.97 · checked October 2026
Ernest Maier — #3 and #4 steel rebar listings — #4 $0.51/ft and #3 $0.31/ft, sold in 20 ft lengths (2026) · checked October 2026
Published 2026 ready-mix plant price sheets (e.g. Gehring Concrete) — $146–$285 per yd³ before fees; short-load fees $50–$200 · checked October 2026
BLS Producer Price Index — ready-mix concrete (via FRED) — +2.3% Sept 2025 → Sept 2026 · checked October 2026
International Residential Code 2021 — R403.1 footings & Table R403.1(1) — 12 × 6 in minimum footing, width by soil bearing, 12 in below undisturbed ground, 3 in cover over bars cast against earth; deck footings R507.3 · checked October 2026

Short answer

8 pads of 18×18×10 in take 0.56 cubic yards of concrete — 28 × 80-lb bags with 10% extra, or 1 yd³ of ready-mix.

Each pad: 18 × 18 × 10 in = 1.88 cu ft (3.13 × 80-lb bags); × 8 = 15 cu ft.

Bags with 10% extra: 28 × 80 lb or 37 × 60 lb — 2,240 lb to move.

Cost: about $181 in bags vs. $485 for 1 yd³ delivered — bags are the obvious choice.

18 in pads spread a post load over more soil — the direction IRC Table R507.3.1 pushes larger decks and weaker soils.

Adjust it to your exact job

Footing type

What are you pouring?

Pads

Number of pads

Common pad sizes (L × W × thick, in)

Length

= 1' 6"

Width

= 1' 6"

Thick

= 10"

You need

28× 80-lb bags

0.61 yd³ of concrete for 8 × 18×18×10 in pads, including 10% extra · 2,240 lb of bags

Concrete volume: 0.56yd³15 ft³ before waste
Per pad: 1.88ft³3.13 × 80-lb bags
Ready-mix order: 1yd³quarter-yard steps, 1 yd minimum
Finished weight: 1.1tons

Code check (IRC 2021)

Thickness 10 in — meets the ruleR403.1.1: footings at least 6 in thick. Deck footing size comes from Table R507.3.1 (load and soil).

Other bag sizes

Bags needed by size
Bag	Bags	Est. cost
40 lb · 0.3 ft³	55	—
50 lb · 0.375 ft³	44	—
60 lb · 0.45 ft³	37	$179
80 lb · 0.6 ft³	28	$181

Bags or a ready-mix truck?

28 bags

$181

Cheaper ✓ · materials only, before tax

1 yd³ delivered

$485

incl. short-load & delivery fees

At these prices a truck becomes cheaper from about 3.25 yd³ (147 bags). Over 1–2 yd³, a truck also saves hours of mixing: plan on 3–4 minutes per bag in a mixer.

That's 1.1 tons of bags — more than most pickups can carry in one trip. Ask about store delivery.

How deep?

Timeline for standard 4000 psi mix

Walk on: 24 hours
Light loads / posts: 24 hours
Keep moist (cure): 5 days ≥70°F · 7 days at 50–70°F
Protect from freezing: 48 hours

Shopping list

28 bags Standard 4000 psi mix — 80-lb bags$181
32 gal Clean water for mixing21–32 gal; start low, never exceed the max

Estimated total$181

Cost estimate

Tap a price to use your store's

80-lb Standard 4000 psi mix
28 bags × $
$181

Materials total$181

Typical U.S. prices checked October 2026. Tap any price to enter your store's.

Size

Cubic yards

80-lb bags

60-lb bags

Bag cost

Ready-mix

12×12×12 in

0.3

$97.05

$485

18×18×10 in

0.56

$181

$485

24×24×12 in

1.19

$350

$570

30×30×12 in

1.85

123

$546

$698

How this was worked out

18 × 18 × 10 = 3,240 cu in per pad, ÷ 1,728 = 1.875 cu ft. Times 8 pads = 15 cu ft, ÷ 27 = 0.556 yd³.

With 10% extra that is 16.5 cu ft ÷ 0.6 cu ft per 80-lb bag = 27.5, rounded up to 28 bags.

At 0.61 yd³ with waste this is a bag job — a truck's 1 yd minimum plus fees would cost about $485.

The full method, material data and tips are on the main concrete footing calculator page.